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Related Terms

  • Acquired immunodeficiency syndrome, AIDS, acute viral nasopharyngitis, antibody, antigen, antihistamine, antiviral, asthma, avian flu, bronchial tubes, bronchitis, CHD, chemotherapy, cholesterol, coronary heart disease, decongestant, dehydration, diabetes, Fahrenheit, fatigue, flu, heart attack, HIV, human immunodeficiency virus, infection, influenza, larynx, malaise, mucous membrane, mucus, otitis media, pandemic, pneumonia, respiratory syncytial virus, rhinoviruses, RSV, sinus, sinusitis, sputum, Strep throat, stress, trachea, transmission, tuberculosis, viral infection, virus.


  • Influenza, commonly referred to as the flu, is a contagious (able to be spread) infection of the respiratory system that is caused by viruses, including influenza type A, B, and C.
  • Influenza viruses are transmitted through the air in tiny droplets when someone with the infection coughs, sneezes, or talks. Individuals are then exposed to the virus through inhalation, or by contact with objects such as telephones, door handles, railings, or computer keyboards. An infection may occur when the virus is then transferred to the eyes, nose, or mouth.
  • In general, the flu is more debilitating than the common cold, and symptoms such as fever, body ache, extreme fatigue (tiredness), and dry cough are seen more in the flu and are more severe. Some influenza viruses can even cause death in otherwise healthy individuals.
  • Although many individuals confuse common colds with influenza because they both affect the upper respiratory system and present with similar symptoms, they are actually caused by different viruses. The upper respiratory system includes the nose, trachea (windpipe), throat, sinuses (air filled spaces in the skull), bronchial tubes (leads from the trachea to the lungs), and larynx (voice box).
  • According to the Centers for Disease Control (CDC), every year in the United States (U.S.), on average five to 20% of the population gets the flu and more than 200,000 people are hospitalized from flu complications, such as dehydration (loss of water), high fever (over 102 degrees Fahrenheit), and extreme fatigue. About 36,000 people die from flu every year.
  • Some patients, such as older people, young children, and people with certain health conditions that lower immunity, including cancer, human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS), are at high risk for serious flu complications.
  • Children are two to three times more likely than adults to get sick with the flu. Also, children frequently spread the virus to others due to bad hygiene, such as sneezing without covering the nose.
  • Treatment for the flu includes bed rest and plenty of fluids, along with symptomatic treatment such as drugs to fight viral infections, reduce fever, and help with sore throat and cough. Prevention includes an influenza vaccine.
  • Flu epidemics: When a flu epidemic occurs, specific populations are infected with a type of influenza virus that has not been encountered before. The immune system of most of the general population cannot respond to the viral infection, and widespread illness and even death can occur. Some individuals, for reasons unknown, may be immune. Epidemics may be restricted to one locale (an outbreak), more general (an “epidemic”), or even global ().
  • Bird flu: An emerging type of virus infecting humans is the avian influenza virus, or bird flu. Several cases of human infection with bird flu viruses have occurred since 1997, mostly in Asia. No human infections with avian influenza A virus have been identified in the United States. The CDC estimates that the death rate for these reported cases has been about 50% in infected humans and 100% in birds. This virus is mainly transmitted to humans through direct contact with live or dead poultry; however, it is thought that a few cases of human-to-human spread have occurred.
  • H1N1: H1N1 is a subtype of the type A influenza virus that causes an illness commonly known as the flu. The H1N1 subtype currently holds much interest because an ongoing pandemic involves a novel (new) strain of the virus. This outbreak began in late March of 2009 in Mexico and is predicted to continue into the regular flu season of 2009-10. According to the U.S. Centers for Disease Control (CDC), as of September 2009, around 9,000 people in the United States have been hospitalized due to novel H1N1 infection, and fewer than 600 deaths are linked to this new virus. It is estimated that a total of one million people have contracted H1N1 flu in the United States. In the southern hemisphere, the seasonal flu period is between April and November. By late August of 2009, the levels of influenza (including H1N1) had returned to normal in the southern hemisphere, according to the World Health Organization.
  • This novel strain was originally referred to as “swine flu” because it appeared similar to influenza viruses that normally infect pigs (swine) and rarely infect humans. There was widespread concern that eating pork or coming into contact with pigs would increase the risks of contracting the novel H1N1 flu. However, later studies showed that this novel H1N1 strain (henceforth, H1N1 or novel H1N1) is quite distinct from influenza viruses that normally infect pigs. It appears that the virus is derived from multiple viruses that may have originated in swine. Novel H1N1 is spread from humans to humans and is not known to be transmitted by eating pork or from close contact with swine. It has not yet been identified in pigs in the United States, and only isolated herds of swine have been infected around the world. Thus, the term “swine flu” is somewhat of a misnomer. Nonetheless, it is still currently used to refer to novel H1N1.

Risk Factors

  • Current health condition: Those individuals who are at high risk and are most susceptible to infection by influenza viruses include those with chronic lung diseases such as asthma, emphysema (lung disease), chronic (long term) bronchitis (inflammation of the bronchial tubes), bronchiectasis (chronic opening of bronchial tubes), tuberculosis (TB, an infection of the lungs), and cystic fibrosis (scar tissue formation in the lungs). Heart conditions such as coronary heart disease (CHD, which includes high blood pressure, high cholesterol, and heart attack), chronic kidney disease, diabetes, severe anemia (decrease red blood cells that carry oxygen), and diseases that depress immunity, such as cancer, human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS) are risk factors for infection with an influenza virus. Drugs such as chemotherapy and steroids lower immune function and can increase susceptibility to developing the flu.
  • Social exposure: Individuals exposed to large volumes of people during the day are also exposed to many viruses including influenza. Children attending school or playing with their peers are at increased risk of influenza infection and transmission. Individuals working for the public and for large businesses with many workers are at an increased risk. Traveling in airplanes or buses also increases the risk of exposure to influenza viruses.
  • Age: Children and the elderly are especially susceptible to the flu. Children’s immune systems have not adjusted to as many viruses as adults, and their bodies are still developing resistance to most microorganisms. Children may not be as careful about cleanliness such as hand washing, and they also tend to spend an increased amount of time with other children, making it easy for viruses to be transmitted from person to person. Individuals residing in nursing homes or long-term care facilities are also at high risk of contracting influenza due to increased chances of exposure. Elderly individuals are at an increased risk for influenza infection due to a decrease in immunity seen in these individuals usually caused by chronic (long-term) health conditions such as heart, lung, and kidney diseases.
  • Flu season: Both children and adults seem to be most susceptible to the flu in the winter months. In cold months when the air is very dry, people turn on their heating systems, drying the air even more. The dry air tends to dry out the mucous membranes in the nose and throat, the first line of defense against the viruses, allowing the viruses to attack the tissue in the nose and throat. Flu season in the United States starts to peak in November and continues to peak through April.
  • Other risk factors affecting immunity: Stress can lower the resistance to infection by depressing the immune system. Stress during PMS or menopause may increase the chances of developing the flu. Low vitamin and mineral levels, such as vitamins A, C, E, the B vitamins, selenium, and zinc may decrease immunity and increase the chances of getting the flu. Very low fat diets also appear to lower the immune system. Sleep helps the body recharge. Proper sleep (eight hours of uninterrupted sleep for an adult) can help keep the body’s immune system healthy helping it to fight off the flu. Bad hygiene, such as not washing the hands before they are placed near the mouth or nose, can contribute to influenza infection and transmission.


  • Influenza virus: Influenza is an infection caused by the influenza virus. There are three major types of influenza viruses that cause the flu, including types A, B, and C. These types are further divided into virus subtypes and then into strains. There are limitless numbers of strains for the influenza viruses that infect humans, because the influenza virus can evolve and change to escape the immune system’s recognition of the virus. When the influenza virus is no longer recognized by the body’s immunity, the virus can re-infect the individual.
  • Type A viruses most commonly affect adults and are the most severe, while type B viruses typically affect children and may also be severe. Type C causes either a very mild illness (usually in children) or no symptoms at all. It does not cause epidemics and does not have the severe public health impact that influenza types A and B do. Bird flu is caused by a type A influenza virus. Novel H1N1 flu is caused by the H1N1 subtype of the type A influenza virus.
  • Every ten years or so, an influenza virus strain appears that is dramatically different from the other members of its family. When this major change occurs, a pandemic (worldwide epidemic) can occur. Very few people have immune systems that are prepared to deal with this radically new virus, so most of the public is very susceptible to becoming ill.

Signs and Symptoms

  • Adults: Mild cases of the flu present with symptoms very similar to the common cold (sneezing, nasal drainage, stuffy nose, sore throat, and low fever). Symptoms usually appear suddenly and may include fevers of 101 degrees Fahrenheit (°F) or above, cough, muscle aches and pains, headache, sore throat, chills and sweats, loss of appetite, fatigue (tiredness), and malaise (general bad feeling). The fever and body aches can last three to five days, and the cough and lack of energy may last for two weeks or more.
  • Most adults recover from the flu within one or two weeks, but others, especially the elderly and those with compromised immune systems (such as HIV/AIDS or cancer patients), may feel weak and debilitated for several weeks after the infection has gone.
  • Children: Flu symptoms in school-age children and adolescents are similar to those in adults. However, children may experience vomiting and diarrhea with the flu, which are rare in adults. Influenza infection in preschool children and infants is difficult to diagnose since its symptoms are so similar to infections caused by other viruses.


  • Physical exam: The flu is usually diagnosed using the typical symptoms, which include cold-like symptoms (runny nose, sore throat, or stuffy nose), a fever of 101 degrees Fahrenheit (°F) or above, cough, muscle ache and pains, headache, sore throat, chills and sweats, loss of appetite, fatigue (tiredness), and malaise (general bad feeling).
  • Those individuals infected by the influenza virus who are otherwise healthy may not need diagnosis by a doctor unless symptoms persist for more than a few weeks or are severe.
  • Laboratory tests: A doctor may do a throat culture, sputum (phlegm from lungs), or blood test to rule out a secondary infection from a bacterium such as Streptococcus (Strep throat) or pneumonia.
  • The most common method for diagnosing the flu is an antigen detection test, which is done by swabbing the nose and throat, then sending a sample to the laboratory for testing. Results are usually available within 30 minutes. This test can determine if an influenza virus is present and what type of virus it is. The results of these tests are helpful in deciding whether pharmacological (drug) treatment is appropriate.


  • If an individual is healthy with a properly functioning immune system, influenza usually is not serious. Although the individual may feel tired and sick, the flu usually goes away within a few days to a few weeks with no lasting effects.
  • Complications of flu arise when the individual’s immune system cannot fight off the viral infection. Complications can include bacterial pneumonia, ear infections, bronchitis (inflammation of the bronchial tubes), sinus infections, dehydration (loss of fluids), and worsening of chronic medical conditions, such as congestive heart failure (CHF), asthma, or diabetes. These complications can be long-term.


  • Healthcare professionals recommend bed rest, adequate liquids, and good nutrition for rapid recovery, and to prevent dehydration (fluid loss). Those individuals infected by the influenza virus who are otherwise healthy may not need treatment by a doctor unless symptoms persist for more than a few weeks or are severe. Treatment for novel H1N1 influenza follows the same guidelines as any other type of flu.
  • There are effective treatments available that can reduce the duration of the symptoms caused by the flu. Over-the-counter (OTC) medications can be purchased without a prescription and may help relieve symptoms associated with the flu, including body aches and pains, stuffy and/or runny nose, and cough. Many products in pharmacies and other retailers contain these medicines separately, or in various combination products. Specific formulations are chosen based upon the patient’s symptoms.
  • Pain relievers and fever reducers: For fever, sore throat, body aches, and headache, acetaminophen (Tylenol®) or ibuprofen (Advil®, Motrin®) may be used over-the-counter. Acetaminophen can cause liver damage, especially if taken chronically, or in doses that exceed four grams daily. Healthcare professionals recommend to carefully follow dosing guidelines when giving acetaminophen to children, as dosing can be confusing. Ibuprofen in prolonged and large doses can cause kidney and liver damage. Also, it is recommended to never give aspirin to children until they reach the age of 18. Aspirin may play a role in causing Reye’s syndrome, a rare but potentially fatal illness in children.
  • Nasal decongestants: Nasal decongestants are useful medications for nasal symptoms, such as “stuffy” nasal passages, associated with the flu. Nasal decongestants help dilate (open) swollen mucous membranes of the nasal passages so the individual can breathe easier. Nasal decongestants include tablets, sprays, inhalers, and nose drops. Nasal decongestants include the oral decongestant pseudoephedrine (Sudafed®), nasal sprays oxymetolazone (Afrin®) and phenylephrine (Neo-Synephrine®), and the nasal inhalers propylhexedrine (Benzedrex®) or levmetamfetamine (Vicks Vapor Inhaler®). They are safe for most patients, but they do have many side effects and conditions in which they should not be used, including in people with heart disease, high blood pressure, thyroid disease, glaucoma (increased pressure in the eyes), diabetes, seizure disorders, enlarged prostate, or by individuals using a monoamine oxidase inhibitor (type of a rarely prescribed antidepressant). Stinging, burning, sneezing, increased nasal discharge, drying of the nostrils, and altered taste may occur. If these effects continue or become bothersome, inform a doctor. Other side effects include rapid or pounding heartbeat, dizziness, trouble sleeping, shaking of the hands, and tremors. Healthcare professionals recommend not using decongestants while pregnant or breastfeeding.
  • Over time, decongestant nose drops, inhalers, and sprays can actually cause rebound congestion, which means the nasal passages are not able to function normally without using these medications. Prolonged use can also cause chronic inflammation of the mucous membranes. Decongestant nasal drops and sprays are not used for more than three days, which helps to stop the potential of nasal rebound.
  • There is widespread national abuse of pseudoephedrine tablets as a drug to make methamphetamine (crystal meth or meth), an illegal drug. Methamphetamine is a highly addictive, synthetically produced central nervous system stimulant with effects similar to cocaine. Meth is the most prevalent synthetic drug manufactured in the United States and is easily produced in home laboratories using common store-bought chemicals. The ease of manufacturing meth and its highly addictive potential has caused the use of the drug to increase throughout the nation. Its use has reached epidemic levels in many parts of the country. National and state laws have attempted to stem this criminal activity by establishing limits on sales of pseudoephedrine. The pharmacist or pharmacy representative may ask for a name and address in many states to prove that the pseudoephedrine is purchased legitimately as a decongestant. There may also be limits on the how much pseudoephedrine can be purchased in one transaction as well as over a certain time period. Pseudoephedrine products may not be available in all states over-the-counter (OTC), and may need to be purchased from behind the pharmacy counter. Also, a new oral nasal decongestant formulation (Sudafed PE®) is available that decreases the potential for abuse. Sudafed PE® contains the nasal decongestant phenylephrine and not pseudoephedrine.
  • Antihistamines: Antihistamines dry up excess nasal secretions (mucus), and in this way help to temporarily stop a runny nose. But they can also cause side effects such as dry mouth, constipation, and drowsiness as well as confusion and increased risk of falls if administered to elderly patients. Non-sedating antihistamines include fexofenadine (Allegra® and cetirizine (Zyrtec®). Antihistamines that cause sedation include diphenhydramine (Benadryl®), clemastine (Tavist®), chlorpheniramine (Chlor-Trimeton®), and brompheniramine (Dimetane®.)
  • Cough syrups: Nonprescription cough syrups, containing various combinations of antihistamines, decongestants, and cough suppressants, are available over-the-counter (OTC) for symptomatic relief of cough associated with the flu. Many doctors strongly discourage the use of these combination medications for any child younger than age two, in whom accidental overdoses could be fatal. Coughs associated with the flu usually last less than two to three weeks. If a cough lasts longer than three weeks, a doctor should be seen. If the cough is productive (brings up mucus), the ingredient guaifenesin can help break up the chest congestion (water intake is also important.) If the cough is dry and hacking, a cough suppressant (dextromethorphan) can stop the cough.
  • Lozenges: Sore throat caused by the flu may be self-treated if the pain is minor. Healthcare professionals recommend not self-treating sore throat for more than two days. Lozenges for sore throat contain active ingredients such as the anesthetics benzocaine, menthol, dyclonine, phenol/sodium phenolate, and hexylresorcinol. Phenol/sodium phenolate and hexylresorcinol also have antibacterial properties.
  • Antiviral drugs: Antiviral medications, including amantadine (Symmetrel®), rimantadine (Flumadine®), zanamavir (Relenza®, inhaled), and oseltamivir (Tamiflu®), have been approved by the United States Food and Drug Administration (FDA) for the treatment and prevention of influenza. When used prophylactically, they are about 70-90% effective in preventing illness in healthy adults. These medications are not used preventatively, due to the potential for influenza viral strains to mutate and become resistant to the drugs.
  • When used as a treatment, it is necessary to begin taking the medication within two days after becoming sick. When used in this manner, these medications can reduce influenza symptoms and may shorten the time an individual is sick by one or two days. They also may make the person less contagious. All of these medications must be prescribed by a doctor and taken for three to five days in a row (five days for oseltamivir and zanamivir). The four antiviral medications are effective against influenza viruses only; they will not help symptoms associated with the common cold or many other unrelated illnesses caused by viruses that circulate in the winter.
  • All of the antiviral medications may be effective for influenza A viruses. However, only zanamavir (Relenza®) and oseltamivir (Tamiflu®) are effective for influenza B viruses. These two also can reduce the symptoms associated with the flu, including fever, body aches and pains, and chills. Recent evidence indicates that a high proportion of currently circulating influenza A viruses in the United States have developed resistance to amantadine (Symmetrel®) and rimantadine (Flumadine®). Antiviral drugs require a prescription.
  • In November 2006, the FDA required the maker of oseltamivir (Tamiflu®) to include a warning that people with the flu, particularly children, may be at increased risk of self-injury and confusion after taking oseltamivir (Tamiflu®). The FDA recommends that individuals with the flu who take oseltamivir (Tamiflu®) be closely monitored for signs of unusual behavior.
  • Antiviral medications can cause side effects, including lightheadedness, nausea, vomiting, loss of appetite, and trouble breathing. If symptoms of the flu (such as fever, aches) get worse, individuals should consult with a doctor.

Integrative Therapies

A Strong scientific evidence

  • Andrographis : Andrographis (Andrographis paniculata) has been widely used in Indian (Hindu) folk medicine and Ayurvedic forms of medicine. Research suggests that andrographis may reduce symptom severity and duration in active respiratory infections if started within 36-48 hours after symptoms develop. Additional studies are needed, especially those that test the effects of andrographis alone for upper respiratory tract infection treatment.
  • Caution is advised when taking andrographis, as adverse effects including drug interactions are possible. Avoid with infertility or patients actively trying to conceive. Use cautiously with diabetes, bleeding disorders, and high or low blood pressure. Use cautiously with blood sugar-altering medications, warfarin or other blood thinning medications, and blood pressure-altering medications. Andrographis should not be used if pregnant or breastfeeding, unless otherwise directed by a doctor.

B Good scientific evidence

  • Echinacea : Although multiple low quality studies have previously suggested that taking echinacea by mouth by adults when upper respiratory tract infection symptoms begin may reduce the length and severity of symptoms, recent data are conflicting. Further research is needed regarding the use of echinacea for treatment of upper respiratory tract infections in adults or prevention of upper respiratory tract infections in adults or children.
  • Avoid if allergic to echinacea, its constituents, or any members of the Asteraceae/Compositae family (ragweed, chrysanthemums, marigolds, daisies). Use cautiously in patients prone to atopic reactions and in those with hemochromatosis and diabetes. Some natural medicine experts discourage the use of echinacea by people with conditions affecting the immune system, such as HIV/AIDS, some types of cancer, multiple sclerosis, tuberculosis, and rheumatologic diseases (such as rheumatoid arthritis or lupus). Use parenteral preparations of echinacea (no longer approved for use in Germany) cautiously. Use tinctures cautiously with alcoholic patients or in patients taking disulfiram or metronidazole. Avoid using echinacea in patients presenting for anesthesia. Use cautiously if pregnant or breastfeeding.
  • Elderberry : Elderberry juice may improve symptoms of influenza such as fever, fatigue, headache, sore throat, cough, and aches. Additional research is needed in this area before a firm conclusion can be reached.
  • Cyanide toxicity is possible. Elderberries must be cooked to prevent nausea or cyanide toxicity. Avoid if allergic to elder or to plants related to honeysuckle. Some reports exist of allergies from contact with fresh elder stems. Use cautiously with diabetes, high blood pressure, urinary problems, or if taking drugs used for any of these conditions. Use cautiously if taking anti-inflammatories, diuretics, or laxatives. Avoid if pregnant or breastfeeding.

C Unclear or conflicting scientific evidence

  • Alizarin : Limited available evidence suggests that alizarin may be of benefit in the treatment of viral infections. Additional research is needed in this area.
  • Avoid if allergic or hypersensitive to alizarin or any plants in the Rubiaceae family. Alizarin may be toxic and should not be handled for long periods of time, rubbed in the eyes, or eaten. Avoid if pregnant or breastfeeding.
  • Andrographis : A combination of andrographis with Siberian ginseng or eleuthero (Eleutherococcus senticosus) called Kan Jang® has been reported effective as part of a regimen to treat influenza in Asian medical systems. Early studies also suggest that andrographis extract may help with upper respiratory tract infection prevention during the winter months if taken daily. Larger studies are required to confirm these results.
  • Caution is advised when taking andrographis, as adverse effects including drug interactions are possible. Avoid with infertility or patients actively trying to conceive. Use cautiously with diabetes, bleeding disorders, and high or low blood pressure. Use cautiously with blood sugar-altering medications, warfarin or other blood thinning medications, and blood pressure-altering medications. Andrographis should not be used if pregnant or breastfeeding, unless otherwise directed by a doctor.
  • Arginine : Arginine, or L-arginine, is considered a semi-essential amino acid because although it is normally synthesized in sufficient amounts by the body, supplementation is sometimes required. Early study suggests that arginine supplements may decrease the risk of respiratory infections. Large, well-controlled studies are needed to clarify this relationship.
  • Avoid if allergic to arginine, or with a history of stroke, or liver or kidney disease. Avoid if pregnant or breastfeeding. Use caution if taking blood-thinning drugs (like warfarin or Coumadin®) and blood pressure drugs or herbs or supplements with similar effects. Blood potassium levels should be monitored. L-arginine may worsen symptoms of sickle cell disease. Caution is advised in patients taking prescription drugs to control sugar levels.
  • Astragalus : Astragalus (Astragalus membranaceus) is often used in Chinese medicine as a part of herbal mixtures to prevent or treat upper respiratory tract infection. Anti-viral activity has been reported in laboratory and animal studies, and in limited human reports. However, most studies have been small and poorly designed. Due to a lack of well-designed research, firm conclusions cannot be drawn at this time.
  • Caution is advised when taking astragalus supplements, as adverse effects including drug interactions are possible. Astragalus should not be used if pregnant or breastfeeding, unless otherwise directed by a doctor.
  • Blessed thistle : Human research of blessed thistle as a treatment for viral infections is lacking. Additional study is needed in this area.
  • Blessed thistle is generally considered to be safe when taken by mouth in recommended doses for short periods of time, with few reported side effects such as birth defects, bleeding, breathing problems, bruising, cancer of the nose or throat, increased production of stomach acid, itching, kidney disease, liver toxicity, skin rash, stomach discomfort, stomach ulcers, and vomiting. Allergic reactions to blessed thistle including rash may occur, as well as cross-sensitivity to mugwort and Echinacea. Cross-reactivity may also occur with bitter weed, blanket flower, Chrysanthemum, coltsfoot, daisy, dandelion, dwarf sunflower, goldenrod, marigold, prairie sage, ragweed or other plants in the Asteraceae/Compositae family. Avoid if pregnant or breastfeeding.
  • Boneset : Boneset (Eupatorium perfoliatum) is native to eastern North America and was used by Native Americans to treat fevers, including dengue fever and malaria. Boneset is used homeopathically, meaning in very dilute amounts. Homeopathic boneset was found in limited available study to decrease symptoms associated with influenza.
  • Homeopathic medicine is regulated by the U.S. Food and Drug Administration (FDA) and is not currently known to have side effects due to the very small amount of active substance used in their preparation. Avoid if allergic or hypersensitive to boneset (Eupatorium perfoliatum), any of its constituents, or related members of the Asteraceae/Compositae family such as dandelion, goldenrod, ragweed, sunflower, and daisies. Use cautiously in small children, elderly individuals, or individuals suffering from a chronic condition. Use cautiously even in the amounts recommended by manufacturers, as boneset may promote sweating, the production of urine, and catharsis. Avoid with known liver or kidney conditions and in patients who ingest moderate to large amounts of alcohol. Avoid if pregnant or breastfeeding.
  • Bovine colostrum : Bovine colostrum is the pre-milk fluid produced from cow mammary glands during the first two to four days after birth. Bovine colostrum confers growth, nutrient, and immune factors to the offspring. Bovine colostrum has shown potential for immune stimulation. However, early evidence has not shown any benefit for treating upper respiratory tract infections, although bovine colostrum may reduce symptoms. Further studies are required before a conclusion can be made.
  • Avoid if allergic to dairy products. Use cautiously because toxic compounds, such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and dichlordiphenyldichloroethylene (DDE), have been found in human colostrum and breast milk. Thus, it is possible that these agents may be found in bovine colostrum. Avoid with, or if at risk of, cancer. Use cautiously with immune system disorders or atherosclerosis (hardening of the arteries). Use cautiously if taking medications, such as anti-diarrheal agents (e.g. Imodium®), insulin, or CNS agents (such as amphetamines, caffeine). Avoid if pregnant or breastfeeding.
  • Chiropractic : Chiropractic care focuses on how the relationship between musculoskeletal structure (mainly the spine) and bodily function (mainly nervous system) affects health. There is currently not enough reliable scientific evidence to conclude the effects of chiropractic techniques on respiratory tract infections.
  • Use extra caution during cervical adjustments. Use cautiously with acute arthritis, conditions that cause decreased bone mineralization, brittle bone disease, bone softening conditions, bleeding disorders, and migraines. Use cautiously with the risk of tumors or cancers. Avoid with symptoms of vertebrobasilar vascular insufficiency, aneurysms, unstable spondylolisthesis, or arthritis. Avoid if taking drugs that increase the risk of bleeding. Avoid in areas of para-spinal tissue after surgery. Avoid if pregnant or breastfeeding due to a lack of scientific data.
  • Cranberry : Limited laboratory research has examined the antiviral activity of cranberry. Further research is warranted in this area.
  • Avoid if allergic to cranberries, blueberries, or other plants of the Vaccinium species. Sweetened cranberry juice may affect blood sugar levels. Use cautiously with a history of kidney stones. Pregnant and breastfeeding women should avoid cranberry in higher amounts than what is typically found in foods.
  • Garlic : Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. However, this has not been demonstrated in well-designed human studies.
  • Avoid if allergic or hypersensitive to garlic or other members of the Lilaceae (lily) family (like hyacinth, tulip, onion, leek, chive). Avoid with a history of bleeding problems, asthma, diabetes, low blood pressure or thyroid disorders. Stop using supplemental garlic two weeks before dental/surgical/diagnostic procedures and avoid using immediately after such procedures to avoid bleeding problems. Avoid in supplemental doses if pregnant or breastfeeding.
  • Ginseng : For more than 2,000 years, the roots of ginseng have been valued in Chinese medicine. Ginseng (CVT-E002) may be safe, well tolerated, and potentially effective for preventing acute respiratory infections and illnesses caused by the flu or the respiratory syncytial virus. More study is needed in this area.
  • Avoid with a known allergy to plants in the Araliaceae family, such as English ivy. There has been a report of a serious life-threatening skin reaction, possibly caused by contaminants in ginseng formulations.
  • Goldenseal : Goldenseal has become a popular treatment for upper respiratory tract infections, and is often added to echinacea in commercial herbal cold remedies. Animal and laboratory research suggests that the goldenseal component berberine has effects against bacteria and inflammation. However, due to the very small amount of berberine in most goldenseal preparations, it is unclear whether goldenseal contains enough berberine to have the same effects.
  • Avoid if allergic or hypersensitive to goldenseal or any of its constituents, like berberine and hydrastine. Use cautiously with bleeding disorders, diabetes, or low blood sugar. Avoid if pregnant or breastfeeding.
  • Guided imagery : Therapeutic guided imagery may be used to help patients relax and focus on images associated with personal issues they are confronting. Experienced guided imagery practitioners may use an interactive, objective guiding style to encourage patients to find solutions to problems by exploring their existing inner resources. Biofeedback is sometimes used with imagery to enhance meditative relaxation. Interactive guided imagery groups, classes, workshops, and seminars are available, as well as books and audiotapes. Preliminary research in children suggests that stress management and relaxation with guided imagery may reduce the duration of symptoms due to upper respiratory tract infections. Additional research is needed to confirm these results.
  • Guided imagery is usually intended to supplement medical care, not to replace it, and guided imagery should not be relied on as the sole therapy for a medical problem. Contact a qualified healthcare provider if mental or physical health is unstable or fragile. Never use guided imagery techniques while driving or doing any other activity that requires strict attention. Use cautiously with physical symptoms that can be brought about by stress, anxiety, or emotional upset because imagery may trigger these symptoms. If feeling unusually anxious while practicing guided imagery, or with a history of trauma or abuse, speak with a qualified healthcare provider before practicing guided imagery.
  • Licorice : Historically, licorice has been used for its expectorant and anti-tussive effects. The herbal combination product, KanJang®, has been studied for the treatment of uncomplicated upper respiratory tract infections. Results are mixed, and additional study is needed.
  • Avoid with a known allergy to licorice, any component of licorice, or any member of the Fabaceae (Leguminosae) plant family. Avoid licorice with congestive heart failure, coronary heart disease, kidney or liver disease, fluid retention, high blood pressure, hormonal abnormalities or in patients taking diuretics. Licorice may cause abnormally low testosterone levels in men or high prolactin or estrogen levels in women. This may make it difficult to become pregnant and may cause menstrual abnormalities.
  • Moxibustion : Moxibustion is the application of heat to various points on the body. It is widely used traditionally in China for treatment of upper respiratory tract infections in children, including colds and flu. However, at this time reliable clinical evidence is insufficient.
  • Individuals not trained in moxibustion should not perform this procedure on themselves or others. Use cautiously over large blood vessels and thin or weak skin. Avoid with aneurysms, any kind of “heat syndrome,” cardiac disease, convulsions or cramps, diabetic neuropathy, extreme fatigue and/or anemia, fever, inflammatory conditions, allergic skin conditions or ulcerated sores, or skin adhesions. Avoid if pregnant or breastfeeding. Avoid areas with an inflamed organ, contraindicated acupuncture points, or on the face, genitals, head, or nipples. Avoid in patients who have just finished exercising or taking a hot bath or shower. Use cautiously with elderly people or with large vessels. It is considered not advisable to bathe or shower for up to 24 hours after a moxibustion treatment.
  • Propolis : Propolis is a natural flavonoid-rich resin created by bees, used in the construction of hives. Propolis is produced from the buds of conifer and poplar trees, in combination with beeswax and other bee secretions. There is some evidence to support the use of propolis for the prevention or treatment of upper respiratory tract infections in children, though current data are generally inadequate. Further research is needed before a clinical recommendation can be made.
  • Avoid if allergic or hypersensitive to propolis, black poplar (Populas nigra), poplar bud, bee stings, bee products, honey, and Balsam of Peru. Severe allergic reactions have been reported. Use cautiously with asthma or gastrointestinal disorders. Avoid if pregnant or breastfeeding because of the high alcohol content in some products.
  • Sorrel : There is currently not enough evidence on the proposed antiviral effects of sorrel. More research is needed.
  • Avoid large doses of sorrel because there have been reports of toxicity and death. This may be because of the oxalate found in sorrel. Many sorrel tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery. These sorrel formulations may cause nausea or vomiting when taken with the prescription drugs metronidazole (Flagyl®) or disulfiram (Antabuse®). Avoid if pregnant or breastfeeding.
  • Thymus extract : Preliminary evidence suggests that both intramuscular and oral thymus extract may be useful for reducing the presence of symptoms associated with respiratory tract infections. Additional study is needed.
  • Avoid if allergic or hypersensitive to thymus extracts. Use bovine thymus extract supplements cautiously. Avoid use with an organ transplant or other forms of allografts or xenografts. Avoid with thymic tumors, myasthenia gravis (neuromuscular disorder), or untreated hypothyroidism. Avoid if receiving immunosuppressants or hormonal therapy. Avoid if pregnant or breastfeeding.
  • Turmeric : Turmeric is a perennial plant native to India and Indonesia, and it is often used as a spice in cooking. Based on early research, turmeric may help treat various viral infections. However, reliable human studies are lacking in this area. Well-designed trials are needed.
  • Avoid if allergic or hypersensitive to turmeric (curcumin), yellow food colorings, or plants belonging to the Curcuma or Zingiberaceae (ginger) families. Use cautiously with a history of bleeding disorders, immune system deficiencies, liver disease, or gallstones. Use cautiously with blood thinners (e.g. warfarin). Use cautiously if pregnant or breastfeeding.
  • Vitamin E : Vitamin E may have a protective effect against colds and influenza. Additional research is needed to better understand the effectiveness of Vitamin E for respiratory infection prevention.
  • Caution is advised when taking vitamin E supplements, as adverse effects including an increase in bleeding and drug interactions are possible. Vitamin E supplements should not be used if pregnant or breastfeeding, unless otherwise directed by a doctor.
  • Wild indigo : Preliminary evidence has shown immunostimulative properties of wild indigo extracts for respiratory tract infections. However, available clinical studies have been conducted using the combination Esberitox N (Echinaceae purpurea radix, Baptisia tinctoria radix and Thuja occidentalis herba). Additional study is needed using wild indigo alone.
  • Avoid if allergic or hypersensitive to wild indigo (Baptisia australis), its constituents, or members of the Fabaceae family. Use cautiously if taking immunosuppressive agents. Avoid if pregnant or breastfeeding.

D Fair negative scientific evidence

  • Echinacea : Initial research suggests that Echinacea may not be helpful for treatment of upper respiratory tract infections in children. Additional research is needed in this area.
  • Avoid if allergic to echinacea, its constituents, or any members of the Asteraceae/Compositae family (ragweed, chrysanthemums, marigolds, daisies). Use cautiously in patients prone to atopic reactions and in those with hemochromatosis and diabetes. Some natural medicine experts discourage the use of echinacea by people with conditions affecting the immune system, such as HIV/AIDS, some types of cancer, multiple sclerosis, tuberculosis, and rheumatologic diseases (such as rheumatoid arthritis or lupus). Use parenteral preparations of echinacea (no longer approved for use in Germany) cautiously. Use tinctures cautiously with alcoholic patients or in patients taking disulfiram or metronidazole. Avoid using echinacea in patients presenting for anesthesia. Use cautiously if pregnant or breastfeeding.


  • Vaccination: Experts suggest that one of the best ways to prevent the flu is to get a flu vaccination each year. New vaccines are created annually to predict the type of influenza that will be most prevalent each year. This is because the genetic makeup of the influenza virus is constantly changing, leading to new types (or strains) of the virus.
  • The virus continually undergoes two different types of changes: antigenic drifts and antigenic shifts. Antigenic drift refers to continual, but gradual, genetic changes in the virus. Influenza types A and B undergo antigenic drift. In contrast, antigenic shift refers to drastic genetic changes that occur quickly. Antigenic shift results in new influenza A virus subtypes in humans. These changes occur as a result of genetic re-assortment, or the re-arrangement of viral genes, when two different virus strains infect a cell at the same time.
  • Traditionally, vaccines have been created through re-assortment, but advancements in reverse genetics may change that. Reverse genetics enables viruses to be created completely from DNA material.
  • There are two types of vaccines, including an injection (flu shot) and a nasal-spray vaccine.
  • The flu shot is an inactivated vaccine (containing killed virus) that is given with a needle. The flu shot is approved for use in people six months of age and older, including healthy people and people with chronic medical conditions such as diabetes, asthma, and heart disease.
  • Target populations for the flu shot include children aged six months to five years, adults that are in close contact with children aged 6 months to five years, such as teachers and day care workers, people 50 years of age and older, healthcare workers, all care givers of high risk people such as those with HIV/AIDS or cancer, and people with chronic health conditions such as asthma, as well as pregnant women.
  • The best period to receive any of the influenza vaccines is soon after the vaccine becomes available in the fall of each year. Flu shots are given yearly to protect individuals against the strain of influenza prevalent for a particular year.
  • The nasal-spray flu vaccine is a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “Live Attenuated Influenza Vaccine”). The nasal flu vaccine is approved for use in healthy people five to 49 years of age who are not pregnant.
  • Flu Mist® is the first nasal spray vaccine for influenza and has been approved by the U.S. Food and Drug Administration (FDA). The live virus is frozen until use. Healthcare professionals recommend thawing in a refrigerator. It should not be refrozen after thawing because of decreased vaccine potency. If the nasal vaccine is not available, the injection can be used where available.
  • A prescription is needed for the influenza vaccine (both injection and nasal forms) and is available from a doctor or various flu clinics.
  • Healthcare professionals recommend that some individuals should not be vaccinated. These include people who have a severe allergy to chicken eggs, people who have had a severe reaction to an influenza vaccination in the past, people who developed Guillain-Barre syndrome (a disorder where the immune system attacks the nervous system) within six weeks of getting an influenza vaccine previously, children less than six months of age (the influenza vaccine is not approved for use in this age group), and people who have a moderate or severe illness with a fever (it is recommended that these patients wait until symptoms lessen to get vaccinated).
  • Cleanliness: Clean the hands thoroughly and often to prevent transmission of the influenza virus. Carrying a bottle of alcohol-based hand rub containing at least 60% alcohol for times when soap and water are not available is a good idea. These gels kill most germs, and are safe for older children to use themselves. Many healthcare professionals recommend not over-using antibacterial soaps and cleansers. The skin contains natural bacteria that can be harmed with repeated use of soaps. Keeping the kitchen and bathroom countertops clean, especially when someone in the family has the flu, is important. Wash children’s toys before and after play when a cold is present in the house. Sneezing and coughing into tissues keeps the viruses from spreading. Used tissues should be discarded right away. A face mask can be worn to protect the individual from the influenza virus and to keep an infected person from transmitting the virus.
  • Avoiding prolonged contact: Healthcare professionals recommend to avoid close, prolonged contact with anyone who has the flu.
  • Careful travel: Traveling to Southeast Asia or to any region with bird flu outbreaks puts an individual at risk. Healthcare professionals recommend the people avoid domesticated birds such as pigeons, avoid open-air markets, and wash the hands, watch children carefully, and stay clear of raw eggs.

Author Information

  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (


Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to Selected references are listed below.

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