Colds and Flu


Colds and influenza are a major concern for health care professionals, especially when dealing with the young, elderly, and immuno-compromised individuals. The elderly in particular can suffer serious consequences from the flu, a leading cause of death in the elderly. Americans spend over one billion dollars annually on nonprescription treatments for coughs and colds, including antipyretics, antihistamines, cough preparations, and decongestants in various combinations. Although these agents may help the symptoms of colds and flu to subside gradually, they do not address the underlying condition, including immune and nutrition status. Also, many of the agents used conventionally for colds and flu may cause unwanted side effects such as insomnia, hyper-excitability, dry mouth, constipation, drowsiness, or interact with prescription medications. There are several reasons for the recommendation of natural therapeutic agents as a first line of defense or as a complement to drug therapy. These reasons include:

    Pre-existing conditions or medications may preclude traditional OTC therapy; Occupation may eliminate the choice of antihistamines or decongestants (pilot, truck driver); Patient may request a natural product due to belief system; Flu vaccination may not provide adequate immune support.

The common cold, also known as upper respiratory infection (URI), is an acute, self-limiting illness caused by a virus. URIs cause absenteeism from work, accounting for 45 million days of restricted activity in 1996. (1) Preschoolers have the highest rate of infection, experiencing 6-10 episodes per year, while adults average 2-4 colds per year. (2)

Although a viral etiology accounts for the overwhelming proportion of cases (with about 30-50 percent being caused by rhinoviruses (rhino = nose) and 10-15 percent being caused by coronaviruses (corona = crown), (3) a secondary bacterial infection may also be present due to lowered host immunity and stress on the system. Incubation periods for viral URIs range from one to five days, with viral shedding lasting up to two weeks. The enveloped viruses may survive for long periods of time outside a host. With the rhinovirus, the home is the primary site for viral transmission. Mechanisms of transmission of colds and influenza include aerosolization of virus-laden respiratory secretions and direct mucous membrane contact with virus from contaminated hands, other skin surfaces and even furniture. Touching the eyes and nose with contaminated hands will increase transmission rates. There is current evidence that psychological stress can increase the risk and severity of viral infections. (4) , (5)

Similarly, influenza is an acute febrile respiratory illness that occurs in annual outbreaks of varying severity. The causative virus infects the respiratory tract and is highly contagious, producing systemic symptoms early in the illness. Influenza viruses belong to the family Orthomyxoviridae and are divided into three types (Types A, B, and C), which are distinguished by the antigenicity of the internal and external proteins of the virus. Type C infection usually causes either a very mild respiratory illness 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. Efforts to control the impact of influenza are aimed at types A and B. Influenza viruses continually change over time, usually by mutation. This constant changing enables the virus to evade the immune system of its host, so that people are susceptible to influenza virus infection throughout life. Influenza is very contagious and is spread by contact with an infected person. A person is contagious from about two days before symptoms occur until about the fifth day of the illness.

No methods have been developed to effectively prevent colds and influenza to date. Vaccines are not likely to be effective in preventing the common cold, due to the large number of immuno-types and the lack of solid immunity to re-infection with the other viruses. Treatment of colds and influenza is largely symptomatic, with antibiotics not recommended for use in the therapy of uncomplicated colds and influenza due to the viral nature of the disease.

A recent resurgence in the use of nutritional supplements including herbs, vitamins, minerals, and homeopathic medicines has provided new options for the support of cold and flu symptoms as well as for prevention. These agents may not prevent a cold, but may result in less severe symptoms and a decreased need for nonprescription or prescription medications. The purpose of herbs and nutritional agents are to improve host defenses before and during viral invasion. By improving immune functionality and host integrity, the individual stands a better chance of fighting off the infection, or at the very least reducing the severity of symptoms associated with a cold or the flu.


World Health Organization, March 19, 2007.

  • Avian flu (H5N1) totals from 2003- March 19, 2007 are 280 confirmed cases and 169 deaths. That's a death rate of more than 55 per cent, which is considered high for a viral illness.
  • Indonesia had the highest number of cases in 2006 with 56 confirmed cases and 46 deaths.

World Health Organization, March 19, 2007.

  • Indonesia had the highest number of cases in 2006 with 56 confirmed cases and 46 deaths.

Influenza: National Institute for Health/Center for Disease Control, Vital Health Statistics, 2001.

    108,000,000 cases are reported annually in the U.S. 1,765 deaths are due to influenza annually. 357 million report restricted activity days. 75 million work days are lost each year. 10,000 to 30,000 people with diabetes die from complications resulting from the flu and pneumonia.

Common Cold: National Institute for Health/Center for Disease Control, Vital Health Statistics Series 10.

    62 million cases are reported yearly. 52.2 million of these affect children under the age of 17. 22 million school days are lost annually. 75% of colds suffered by children under 5 are medically attended.

Signs and Symptoms

[span class=alert]The following list does not insure the presence of this health condition. Please see the text and your healthcare professional for more information.[/span]

Symptoms of colds may include rhinorrhea, sneezing, nasal stuffiness, throat clearing, postnasal drip, cough, and nasal obstruction. A sore throat and/or cough may also be present. Other symptoms may include coryza, pharyngitis, laryngitis, headache, malaise, and fever, usually in various combinations. Ear and sinus problems are often present as well, but these symptoms are usually caused by mucosal edema, which impairs drainage.

Postulated that the unwanted symptoms of colds (i.e. rhinitis) are produced by a viral cytopathic effect that destroys the nasal mucosa. However, one study found that the histological appearance of the nasal mucosa in biopsies taken during colds could not be distinguished from biopsies taken two weeks after the illness, except for a few increased number of polymorphonuclear leukocytes (PMNs) during the cold. (6) In one study, rhinovirus and coronavirus were found not to be destructive of nasal epithelium in vitro. Another hypothesis states that a viral infection of the nose triggers a cascade of inflammatory mediators that result in the common symptoms of colds. (7)

Influenza virus can produce clinical syndromes, such as the common cold, pharyngitis, tracheobronchitis, and pneumonia. Symptoms of influenza include chills, fever, headache, muscular aches/pains, malaise and fatigue, and lack of appetite.

Common Cold

    Rhinorrhea Sneezing Nasal stuffiness Throat clearing Postnasal drip Cough Nasal obstruction Sore throat Coryza Pharyngitis Laryngitis Headache MalaiseFever Ear and sinus problems


    Chills Fever Headache Muscular aches/pains Malaise Fatigue Lack of appetite

Treatment Options


Vaccination - According to the CDC, the influenza vaccine has been shown to reduce hospitalization by about 70 percent and death by about 85 percent in the non-institutionalized elderly. Among nursing home residents, the flu vaccine can reduce the risk of hospitalization by about 50 percent, the risk of pneumonia by about 60 percent, and the risk of death by 75 to 80 percent. However, influenza in the elderly is still ranked as one of the top ten causes of death in those over the age of 65 years. (8) Documented side effects from administration of influenza vaccines range from mental confusion, fatigue, circulatory problems, headache, sexual disturbances, and gastrointestinal complaints among others. (9) About 5-10 percent may experience mild side effects, such as headache or low-grade fever for a short period of time. For some elderly, the vaccine does not provide adequate protection, and therefore, are still at risk and should consider taking additional steps to be prepared for flu season.

Antiviral agents

    Amantadine and rimantadine - chemically related moieties that interfere with the replication cycle of influenza type A viruses. They are not effective against influenza type B or other viral respiratory pathogens. Amantadine- and rimantadine-resistant influenza A viruses can emerge when either of these drugs is administered for treatment; amantadine-resistant strains are cross-resistant to rimantadine and vice versa. There is no evidence that amantadine- or rimantadine-resistant viruses are more virulent or more transmissible than amantadine- or rimantadine-sensitive viruses. Amantadine and rimantadine may cause central nervous system (CNS) and gastrointestinal side effects in some persons. The incidence of CNS side effects is higher among persons taking amantadine than among those taking rimantadine. Such adverse reactions are rarely severe, but may be important for some categories of patients. Serious side effects, such as marked behavioral changes, delirium, hallucinations, agitation, and seizures, have been observed. These more severe side effects have been associated with high plasma drug concentrations and have been observed most often in elderly persons, and persons with renal insufficiency, seizure disorders, or certain psychiatric disorders, who have been taking amantadine for prevention at a dose of 200mg per day. Zanamivir and oseltamivir - new antiviral agents indicated for the treatment of uncomplicated influenza A and B viruses. These agents are viral neuramidase inhibitors, a critical protein of the surface membrane of the influenza virus, which enables the replicated flu virus to bud from the host cells in the respiratory tract. Inhibition of viral neuramidase prevents newly formed flu virus from escaping the infected cells, interrupting the spread of the infection. To date, reported side effects have been transient, including GI upset, nausea, vomiting, and diarrhea.

Nutritional Supplementation

Vitamin C

Vitamin C may be utilized at 4 - 6 times the normal rate by white blood cells during active infection. Vitamin C’s role in colds and influenza is not curative, but it does support a healthy immune system response to viral and bacterial infection. A meta-analysis of sixteen controlled studies evaluating the effects of vitamin C on the common cold provided positive results in decreasing the symptoms and severity of the common cold. Participants ingesting 1gm or more of vitamin C daily reported an overall 40 percent reduction in the symptoms and severity of colds. (10) A meta-analysis of 21 placebo-controlled studies from 1971 to 1993 reported similar results. Although there was no reduction in incidence, individuals, ingesting 1,000mg or more of vitamin C daily reduced the duration of episodes and the severity of symptoms of the common cold by an average of 23 percent. (11) In a double-blind, placebo-controlled survey 168 volunteers received a placebo or vitamin C with both groups taking 2 tablets a day for 60 days. The results were that the active-treatment group experienced significantly fewer colds and recovery if infected was faster than the placebo group. (12)

There is evidence indicating that vitamin C may play an important role in the efficient functioning of the immune system. The results of a study where levels of various types of immunoglobulins (IgA, IgG, IgM) were reported to increase with regular ingestion of 1 gram of vitamin C for 75 days. (13) Regular consumption of vitamin C has also been reported to increase interferons and lymphocytes in human subjects. (14) , (15) Vitamin C demands rise to 5-6 times normal levels within the white blood cells when fighting an infection. Therefore, an increase in Vitamin C during a cold or the flu may be warranted.

Vitamin E

Poor immune response, especially cytokine production and T-cell mediated immune function, has been associated with low levels of vitamin E. (16) Lack of vitamin E is also thought to increase free radical lipid peroxidation, particularly in the elderly. Research has also found that vitamin e may reduce the occurance of the common cold in the elderly. (17)


Human clinical trials on the use of zinc in colds and influenza indicate that zinc gluconate lozenges may be effective in reducing the duration and severity of symptoms. (18) In a meta-analysis of seven randomized, controlled trials, it was determined that zinc gluconate lozenges have a therapeutic effect in treating the common cold. (19) Zinc’s mechanism of action against the human rhinovirus (HRV) involves free ionic zinc (Zn+2), which complexes with proteins of critical nerve endings and surface proteins of the HRV. These complexes interrupt nerve impulses and also block the ability of the rhinovirus to attach to the intercellular adhesion molecule-1 (ICAM-1). This action reportedly interrupts the human rhinovirus infection and reduces the inflammatory processes. (20) The rapid reduction in cold symptoms when taking zinc lozenges is probably due to the inhibition of these inflammatory processes. Zinc is also important because of its role in maturing T-killer cells in the thymus. Individuals deficient in zinc may undergo thymic involution, and therefore, not mature T-killer cells to a fully functioning state.


Many food sources today do not contain the vitamins and minerals that they did in the past, and in particular, the elderly population is known to have suspect nutrient status. Recommending a multiple vitamin daily is the first choice for prevention. Studies support that elderly individuals taking a daily multiple vitamin have a reduced risk for colds and flu. (21)

Thymus Gland Extract

The thymus gland is one of the most important components of the immune system. Thymic lymphoidal cells, or T cells, mature in the thymus gland and enter the circulatory system. Thymus glandular extracts contain small amounts of all the immune components of the thymus gland, with a purpose of enhancing and supporting immune function. Thymus glandular extracts are reported to be useful in chronic viral infections, autoimmune disease, and to support immune function in colds and influenza. (22) Product quality is variable from company to company, and the manufacturing process influences the end product.

Sterols (Sitosterol) and Sterolins (Sitosterolin)

There are many chemical constituents (termed phytochemicals) found in plant medicines that have beneficial pharmacological effects in humans. Some bioactive phytochemicals include tannins, resins, polysaccharides, saponins, glycosides and volatile oils among others. Recent literature has reported that two of these phytochemicals, sterols and sterolins (plant "fats"), occur naturally in fruits, vegetables, seeds and nuts, have clinically beneficial effects in human subjects in many conditions.

Sterol is found in all plant-based foods, and sterolin is a glucoside moiety joined to the sterol chemical structure. Both sterols and sterolins were identified as early as 1922. In the natural state, these plant "fats" are bound to the fibers of the plant, making the sterols and sterolins difficult to be absorbed during the normal transit of digested food through our gut. Seeds are the richest source of the sterols and sterolins, but are usually removed during processing by the food industry.

Plant sterols and sterolins have been reported to be effective adjunctive agents in the management and treatment of disease states such as high cholesterol levels, benign prostatic hyperplasia, pulmonary tuberculosis and stress-induced immune suppression and HIV among others. (23) , (24) , (25) , (26) , (27) Some of the most promising uses of these plant "fats" is in the management of autoimmune disorders such as lupus, multiple sclerosis, rheumatoid arthritis and myasthenia gravis. Of note is that the sterols should be combined with sterolin in order to be an effective agent for the immune system. (28)

Sterols and sterolins have been reported to modulate the function of T-cells, significantly enhancing the proliferation of the CD-4 TH-1 cells and increasing the production of the interleukin 2 (IL2) and gamma-interferon (FN-g and IFN-y). (29) These results indicate that sterols and sterolins are adaptogenic in that they modulate the immune and stress response.

Care should be taken if an individual is taking immunosuppressive agents. Based on pharmacology, if an individual is taking hypocholesterolemic agents concurrently with plant sterols and sterolins, a dosage adjustment in the pharmaceutical medication may be necessary.

Herbal Supplementation


Echinacea is one of the most popular herbs in the world. It has non-specific stimulatory effects on the immune system. (30) Research has reported that echinacea may stimulate the alternate and complementary pathway of the immune system, activating white blood cells and macrophages for use in the management and treatment of colds and influenza. (31) , (32) Echinacea is also reported to possess antimicrobial activity against bacteria, fungi, and viruses. (33) There have been several randomized, double-blind, placebo controlled clinical studies in Europe conducted on human subjects using echinacea. Benefits reported include improving the symptoms and severity of colds and influenza. (34) , (35) , (36) , (37) , (38) The reported bioactive constituents include: polysaccharides including echinacin, inulin, and arabinogalactan; caffeic acid; glycoside derivatives including echinacosides, isobutylamides (echinacein and others); essential oils (including humulene, borneol, vanillin); sesquiterpene lactone esters; alkaloids; flavonoids; and others. (39) , (40)

A randomized controlled trial of the effect of echinacea on the incidence and severity of colds and respiratory infections was tested in 109 patients. (41) The liquid succus product of Echinacea purpurea was used in this study. It was determined that treatment with the echinacea succus product does not significantly decrease the incidence, duration, or severity of colds and respiratory infections compared to placebo. However, earlier studies have used the same succus product in double-blind, placebo controlled clinical trial with positive results (the preparation decreased the duration of the common cold). Another study has also reported echinacea is ineffective in treating rhinovirus. (42) The authors reported no significant advantage when using the echinacea product on either the occurrence or severity of the illness. However, the product used in this study may have resulted in sub-therapeutic results.

It should be noted that the immuno-modulating polysaccharides found in the echinacea plant are NOT soluble in alcohol. Therefore, when recommending an echinacea product, it is best not to use alcohol liquid extracts of echinacea due to precipitation of the polysaccharide content and possible loss of the immuno-modulatory properties.


Goldenseal has a long history of use in the United States as a medicinal herb, traditionally for GI disturbances, as an anti-infective agent, and to stimulate bile flow. (43) , (44) , (45) It was initially used by Native Americans and gained popularity with the eclectic medical movement from the 1850s to the 1940s. Most of the current use of goldenseal is for colds and influenza. Combinations of golden seal and echinacea are one of the leading selling herbal supplements in the U.S. market today. Due to the mucous membrane tonifying and the antibacterial properties of the alkaloids in golden seal, this herbal medicine may be useful in managing symptoms associated with colds and influenza. (46) , (47) Berberine, one of the main alkaloids in golden seal, has been reported to exert fever-fighting effects by increasing the immune system’s ability to process fever-producing compounds that are released by pathogens. (48) Strong evidence for the support of goldenseal in colds and flu is still lacking; yet, anecdotally, it remains one of the most popular agents on the market.


Elder has been used as a food and medicinal agent for thousands of years. The flower and berry have been traditionally used in the prevention and treatment of colds, influenza, chronic nasal inflammation, and sinusitis. (49) An extract of the berries of the black elder (Sambucus nigra) has been reported to inhibit the ability of several strains of influenza virus to replicate. It does this by coating the spike-like projections on the virus, preventing it from injecting protein into the host cell membrane. In one study using a liquid extract of elder berry, 90 percent of the individuals with symptoms of influenza B were asymptomatic in 2-3 days, while individuals on placebo did not recover for at least 6 days. (50) Antioxidant properties of elderberry are related to the flavonoid constituents.


The Chinese have valued astragalus for centuries for its immune-enhancing and adaptogenic properties. As an adaptogen, it may modify and improve the body’s response to stress through action on the adrenal cortex. (51) , (52) Studies have reported that astragalus promotes regeneration of cells in the bronchi after viral infection. (53) This potential benefit could help with the lingering phase of bronchial weakness as seen in some individuals with colds and influenza. Astragalus should be able to be taken safely for several months without the risk of suppressing immunologic function. The polysaccharides contained in astragalus are reported to improve natural killer and T-cell function, as well as interferon production by the immune system. (54) Studies have reported that administration of astragalus for one month increased phagocytosis by spleen cells, decreased T-suppressor cell function, and improved T-killer cell function. (55) Astragalus enhances the effects of interferon, and may act not only to improve resistance to colds but decrease the duration of a cold. (56)

Larch Arabinogalactan

Larix is a purified extract of the bark from the Western larch tree. It contains the phytochemical arabinogalactan, an immunomodulating polysaccharide that is also found in Echinacea spp. Larix has been reported to increase NK cells, stimulate the reticuloendothelial system, stimulate macrophage activation, and have antiviral effects in-vitro. (57) Larix has also been used with positive success in children, specifically in otitis media. (58)


Aconitum napellus

Typical Dosage: 6X or 6CSudden onset, especially after exposure to cold wind; Sneezing; Burning throat, worse at night

Anas barbariae(hepatis et cordis extractum)

Typical Dosage: 200COnset of flu symptoms including fever, chills, muscle aches, headache


Typical Dosage: 6X or 6C, 30X or 30CSudden onset; High temperature; Eyes sensitive to light, red; Hot face, burning; Sore throat worse on right side

Bryonia alba

Typical Dosage: 6X or 6C, 30X or 30CFlu-like symptoms with fever, intense thirst, muscle aches, fatigue, headache; Worse from slightest movement

Ferrum phosphoricum

Typical Dosage: 6X or 6C, 30X or 30CCold comes on slowly; Mild fever; Prone to nosebleeds

Gelsemium sempervirens

Typical Dosage: 6X or 6C, 30X or 30CFever and flu-like symptoms; Sluggish and achy with chills

Mercurius vivus

Typical Dosage: 6X or 6C, 30X or 30CvSweating; Sneezing; Excessive salivation; Thick yellowish-green mucus; Bad breath

Natrum muriaticum

Typical Dosage: 6X or 6C, 30X or 30CCold in early stages; Repeated sneezing; Thin clear mucus; Stuffy nose; Cold sores

Acupuncture & Acupressure

Chen Su used Yin Tang (Extra 2) to treat 100 patients for colds and flu. He used 1" 30-31 guage acupuncture needles. After insertion, he manipulated them for about 1 minute to gain sedating effects. He then left the needles in place for 20-30 minutes, turning the needles every 5-6 minutes. Three days was one treatment unit. 77 cases significantly improved, 19 improved, and 4 did not respond for an effectiveness rate of 96%, compared to the control group (p


Aromatherapy for Colds and Flu

The various symptoms of colds and flu may respond well to the use of essential oil therapy. Depending on the symptom being addressed, the oils should be used in a bath or diffuser.

To relieve sinus congestion:

  • Eucalyptus (Eucalyptus globules) 5 drops
  • Lemon (Citrus Limonum) 3 drops Pine (Pinus sylvestris) 2 drops Tea tree (Melaleuca alternifolia) 1 drop

To relieve general flu symptoms:

    Cedarwood (Juniperus mexicana scheide) 4 drops Eucalyptus (Eucalyptus globules) 4 drops Vertiver (Vetivera zizanoides) 3 drops Lemon (Citrus Limonum) 2 drops

To relieve sore throats, a gargle made by adding the following oils to 4 ounces of warm water may be useful:

    Clary sage (Salvia sclerea) 1 drop Eucalyptus (Eucalyptus globules) 1 drop Myrrh (Commiphora Myrrha) 1 drop

Caution: Essential oils should not be used during pregnancy or lactation except under the guidance of a trained aromatherapist or healthcare practitioner.

Traditional Chinese Medicine

Colds and Flu

Extensive information regarding the treatment of this health condition using Traditional Chinese Medicine is available through the link above.

Diet & Lifestyle

    Drink at least 6-8 glasses of quality water daily. Avoid refined sugars. Take in clear broth and soups. Take steps to reduce chronic stress. Get adequate rest. Try to eat more nutrient rich foods, especially fruits and vegetables. Reduce sugar intake. Exercise regularly.

Clinical Lab Assessment

Some of the following laboratory testing can provide information necessary for diagnosis and treatment. In addition, the tests listed may also give insight to functional metabolism and functional nutrient status in the body.

Adrenal Function Profiles

Adrenal insufficiency can contribute to impaired resistance to infection. Stress activates the HPA axis and has impact on the immune system, particularly through the adrenal hormones. In assessing the HPA axis, adrenal functional abnormalities are relatively simple to identify and address (e.g., when compared to hypothalamic dysregulation or pituitary imbalance).

Thyroid Profile

Low thyroid function can result in poor resistance to infections. Assessment of thyroid hormone production, peripheral hormone conversion, cellular sensitivity response, thyroid hormone antibody activity, and hormone feedback response mechanisms can provide critical information for intervention with a goal of optimal function.

Organic Acids

Organic acids analysis is a useful method for measurement of biochemical intermediates in urine. These intermediates can offer information about key enzyme functions and nutrient competence (amino acids, nutrient cofactors, minerals, and fatty acids). A subset of organic acids, the dysbiosis markers, may provide useful information regarding gastrointestinal pathogens that can contribute to immune compromise.


Plasma or salivary cortisol measurements can be used as a marker in the evaluation of stress syndromes that may relate to increased susceptibility to infections.

Clinical Notes

    If an antibiotic is given, recommend the use of probiotic acidophilus/bifidus 10-20 billion units, twice a day, two hours apart from the antibiotic dose. This may reduce the risk of antibiotic induced diarrhea. Ensure adequate nutrition status with a multivitamin. Additional vitamin C should be considered. The sooner homeopathy is implemented with the onset of symptoms, the better the effect. Homeopathics can be combined with herbal and nutritional approaches. Consider echinacea or elder as the primary herb for recommendation. Goldenseal is secondary if there is upper respiratory involvement. Combination products may contain two or more of these agents or related products. Diabetics may need zinc first because of already established compromised zinc status. Homeopathics should be considered as a first line of defense for at risk populations, multiple drug users, and for individuals who cannot risk side effects of conventional therapy due to occupation.


  1. National Institute of Allergy and Infectious Disease, National Institute of Health. Common Cold Fact Sheet. Mar2001.
  2. National Institute of Allergy and Infectious Disease, National Institute of Health. Common Cold Fact Sheet. Mar2001.
  3. View Abstract: Makela MJ, et al. Viruses and bacteria in the etiology of the common cold. J Clin Microbiol. 1998;36(2):539-42.
  4. View Abstract: Padgett DA, et al. Stress exacerbates age-related decrements in the immune response to an experimental influenza viral infection. J Gerontol A Biol Sci Med Sci. 1998;53(5):B347-53.
  5. Gruzelier J, et al. Mind-body influences on immunity: lateralized control, stress, individual differences predictors, and prophylaxis. Ann N Y Acad Sci. 1998;851:487-94.
  6. View Abstract: Winther B, et al. Histopathologic examination and enumeration of polymorphonuclear leukocytes in the nasal mucosa during experimental rhinovirus colds. Acta Otolaryngol Suppl (Stockh). 1984;413:19-24.
  7. View Abstract: Winther B, et al. Viral-induced rhinitis. Am J Rhinol. 1998;12(1):17-20.
  8. National Vital Statistics Reports, Vol 48, No. 11. Jul2000.
  9. Palache AM. Influenza subunit vaccine - ten years experience. Eur J Clin Res. 1992;3:117-138.
  10. Pauling L. How to Live Longer and Feel Better. New York: WH Freeman and Company; 1987:118-21.
  11. View Abstract: Hemila H. Does vitamin C alleviate the symptoms of the common cold? – A review of current evidence. Scan J Infec Dis. 1994;26(1):1-6.
  12. View Abstract: Van Straten M, Josling P. Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey. Adv Ther. May2002;19(3):151-9.
  13. View Abstract: Prinz W, et al. The effect of ascorbic acid supplementation of some parameters of the human immunological defense system. Int J Vit Nutr Res. 1977;47:248-256.
  14. Yonemoto RH, et al. Enhanced lymphocyte blastogenesis by oral ascorbic acid. Proceedings of the American Association for Cancer Research. 1976;17:288.
  15. View Abstract: Dahl H, et al. The effect of ascorbic acid on production of human interferon and the antiviral activity in vitro. Acta Pathol Microbiol Scan [B]. 1976;84B:280-84.
  16. View Abstract: Meydani SN, et al. Antioxidant modulation of cytokines and their biologic function in the aged. Z Ernahrungswiss. 1998;37(1):35-42.
  17. View Abstract: Meydani SN, et al. Vitamin E and Respiratory Tract Infections in Elderly Nursing Home Residents. JAMA. Aug 2004;292(7):828-836.
  18. View Abstract: Garland ML, et al. The role of zinc lozenges in the treatment of the common cold. Ann Pharmacother. 1998;32:63-69.
  19. View Abstract: Marshall S. Zinc gluconate and the common cold. Review of randomized controlled trials. Can Fam Physician. 1998;44:1037-42.
  20. View Abstract: Novick SG, et al. Zinc-induced suppression of inflammation in the respiratory tract, caused by infection with HRV and other irritants. Med Hypotheses. 1997;49(4):347-57.
  21. View Abstract: Girodon F, Galan P, Monget AL. Impact of Trace Elements and Vitamin Supplementation on Immunity and Infections in Institutionalized Elderly Patients. Arch Intern Med. 1999;159:748-754.
  22. View Abstract: Kosmala M, et al. Pharmacological Properties of the Extract of Thymus Gland (Thymomodulin-TFX) and Its Effects on Reproduction. Acta Pol Pharm. 1993;50(6):447-52.
  23. Bouic PJD. Immunomodulation in HIV/AIDS: The Tygerberg/Stellenbosch university experience. AIDS Bulletin. Sept1997;6(3):18-20.
  24. Clerici M, Bevilacqua M, Vago T, et al. An Immunoendocrinological Hypothesis of HIV Infection. Lancet. Jun1994;343:1552-1553.
  25. View Abstract: Donald PR, Lamprecht JH, Freestone M, et al. A Randomized Placebo-controlled Trial of the Efficacy of Beta-sitosterol and Its Glucoside as Adjuvants in the Treatment of Pulmonary Tuberculosis. International Journal of Tuberculosis and Lung Disease. Jul1997;1(5):518-522.
  26. View Abstract: Berges RR, Windele J, Trampisch HJ, et al. Randomized, Placebo-controlled, Double-blind Clinical Trial of B-sitosterol in Patients with Benign Prostatic Hyperplasia. Lancet. Jun1995;345(8964):1529-32.
  27. View Abstract: Plat J, Kerckhoffs DA, Mensink RP. Therapeutic Potential of Plant Sterols and Stanols. Curr Opin Lipidol. Dec2000;11(6):571-6.
  28. View Abstract: Plat J, Kerckhoffs DA, Mensink RP. Therapeutic Potential of Plant Sterols and Stanols. Curr Opin Lipidol. Dec2000;11(6):571-6.
  29. View Abstract: Plat J, Kerckhoffs DA, Mensink RP. Therapeutic Potential of Plant Sterols and Stanols. Curr Opin Lipidol. Dec2000;11(6):571-6.
  30. Snow JM. Echinacea (Moench) spp. Asteraceae. Protocol Journal of Botanical Medicine. 1996;2(2):18-23.
  31. View Abstract: Vomel VT. The effect of a nonspecific immunostimulant on the phagocytosis of erythrocytes and ink by the reticulohistiocyte system in the isolated, perfused liver of rats of various ages. Arzneim Forsch/Drug Res. 1984;34:691-95.
  32. View Abstract: See DM, et al. In vitro effects of echinacea and ginseng on natural killer and antibody-dependent cell cytotoxicity in healthy subjects and chronic fatigue syndrome or acquired immunodeficiency syndrome patients. Immunopharmacology. 1997;35(3):229-35.
  33. Wichtl M, in N. A. Bisset, ed. Herbal Drugs and Phytopharmaceuticals. Stuttgart: Scientific Press; 1994:182-84.
  34. Schoneberger D. The influence of immune-stimulating effects of pressed juice from Echinacea purpurea on the course and severity of colds. Forum Immunologie. 1992;8:2-12.
  35. Braunig B, et al. Echinacea purpurea root for strengthening the immune response in flu-like infections. Zeitschrift Phytother. 1992;13:7-13.
  36. Braunig B, et al. Therapeutical experiences with Echinacea pallida for influenza-like infections. Naturheilpraxis. 1993;1:72-75.
  37. View Abstract: Grimm W, et al. A Randomized Controlled Trial of the Effect of Fluid Extract of Echinacea purpurea on the Incidence and Severity of Colds and Respiratory Infections. Am J Med. Feb1999;106(2):138-43.
  38. View Abstract: Brinkeborn RM, et al. Echinaforce and Other Echinacea Fresh Plant Preparations in the Treatment of the Common Cold. A Randomized, Placebo Controlled, Double-blind Clinical Trial. Phytomedicine. Mar1999;6(1):1-6.
  39. View Abstract: Bauer R, et al. Analysis of alkamides and caffeic acid derivatives from Echinacea simulata and E. paradoxa roots. Planta Medica. 1991;57:447-449.
  40. View Abstract: Wagner H, et al. Immunstimulerend wirkende polysaccharide (heteroglykane) aus hoheren Pflanzen. Arneim-Forsch. 1985;35:1069-1075.
  41. View Abstract: Grimm W, et al. A Randomized Controlled Trial of the Effect of Fluid Extract of Echinacea purpurea on the Incidence and Severity of the Colds and Respiratory Infections. Am J of Medicine. 1999;109:139-143.
  42. View Abstract: Turner RB, et al. Ineffectiveness of echinacea for prevention of experimental rhinovirus colds. Antimicrob Agents Chemother. Jun2000;44(6):1708-9.
  43. Sabir M, et al. Study of some pharmacological actions of berberine. Indian J Physiol Pharmacol. 1971;15(3):111-32.
  44. Newall CA, et al. Herbal Medicines: A Guide for Health Care Professionals. London, England: The Pharmaceutical Press; 1996:151-52.
  45. View Abstract: Berberine. Altern Med Rev. Apr 2000;5(2):175-7.
  46. View Abstract: Zhang MF, et al. Antidiarrheal and anti-inflammatory effects of berberine. Chung Kuo Yao Li Hsueh Pao. 1989;10(2):174-76.
  47. View Abstract: Sun D, et al. Berberine sulfate blocks adherence of Streptococcus pyogenes to epithelial cells, fibronectin, and hexadecane. Antimicrobial Agent and Chemotherapy. 1988;32(9):1370-1374.
  48. Sabir M, et al. Study of Some Pharmacological Actions of Berberine. Indian J Physiol Pharmacol. 1971;15(3):111-32.
  49. Newall CA, et al. Herbal Medicines: A Guide for Health Care Professionals. London, England: The Pharmaceutical Press; 1996:151-52.
  50. View Abstract: Zakay-Rones Z, et al. Inhibition of several strains of influenza virus in-vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B in Panama. J Altern Complement Med. 1995;1(4):361-369.
  51. Chang CY, et al. Effects of Astragalus membranaceus on enhancement of mouse natural killer cell activity. Chung Kuo I Hsueh Ko Hsueh Yuan Hsueh Pao. 1983;5(4):231-34.
  52. View Abstract: Zhao KS, et al. Positive modulating action of shengmaisan with Astragalus membranaceus on anti-tumor activity of LAK cells. Immunopharmacology. 1990;20(3):471.
  53. Chang H, et al. Pharmacology and Application of Chinese Materia Medica. Singapore; Chinese University of Hong Kong. World Scientific. 1987:4.
  54. View Abstract: Chu DT, et al. Immune restoration of local xenogeneic graft-versus-host reaction in cancer patients in in-vitro and reversal of cyclophosphamide-induced immune suppression in the rat in vivo by fractionated Astragalus membranaceus. Chung Hsi I Chieh Ho Tsa Chih. Jun1989;9:351-54.
  55. View Abstract: Chu DT, et al. Immune Restoration of Local Xenogeneic Graft-versus-host Reaction in Cancer Patients in In-Vitro and Reversal of Cyclophosphamide-induced Immune Suppression in the Rat in vivo by Fractionated Astragalus membranaceus. Chung Hsi I Chieh Ho Tsa Chih. Jun1989;9:351-54.
  56. Geng CS, et al. Advances in immuno-pharmacological studies on Astragalus membranaceus. Chung Hsi I Chieh Ho Tsa Chih. 1986;6(1):62-64.
  57. View Abstract: Hauer J, et al. Mechanism of Stimulation of Human Natural Killer Cytotoxicity by Arabinogalactan from Larix occidentalis. Cancer Immunol Immunother. 1993;36(4):237-44.
  58. View Abstract: Kelly GS. Larch Arabinogalactan: Clinical Relevance of a Novel Immune-enhancing Polysaccharide. Altern Med Rev. Apr1999;4(2):96-103.