~ Colds and Flu - Proposed Treatments

A cold is a respiratory infection caused by one of hundreds of possible viruses. However, because these viruses are so widespread, it is perhaps more accurate to say that colds are caused by a decrease in immunity that allows one of these viruses to take hold.

Colds occur more frequently in winter, but no one knows exactly why. Nearly everyone catches colds occasionally, but some people catch colds quite frequently, and others tend to stay sick an unusually long time.

Influenza B, commonly called “the flu,” occurs in the form of a worldwide epidemic every winter. The predominant symptoms of flu are fever, malaise, and muscle aches. Cold-like respiratory symptoms are usually fairly minor with the flu. However, a dangerous type of pneumonia can develop as a complication of influenza, especially in seniors.

Conventional medicine can neither cure nor prevent the common cold. Furthermore, none of the over-the-counter treatments have been found to shorten the duration of a cold or even provide significant temporary relief. Cough syrup, in fact, seems to be no better than placebo. 111,112 Some of the natural treatments described in this section may be able to do better.

People often want to take antibiotics for colds, and many physicians will prescribe them —- even though antibiotics have no effect on viruses. Many believe that when the mucus turns yellow, it means that a bacterial infection has occurred for which antibiotic treatment is indicated. However, viruses can also produce yellow mucus, and even if bacteria have made a home in the excess mucus, they may be only innocent bystanders and produce no symptoms.

Colds, however, can be complicated by bacterial infections. In such cases antibiotic treatment may be indicated.

The situation is somewhat better for influenza. The “flu shot” provides protection against influenza B, but it is often not full protection, and in recent years it has not always been available in full supply. A variety of prescription medications can help prevent both influenza B and influenza A (a relatively less dangerous relative of influenza B), and also reduce their length and severity if you do come down with them.

Principal Proposed Natural Treatments

Remember the old saying "a cold lasts seven days, but if you treat it properly you will get over it in a week"? Actually, it may be possible to prove folk wisdom wrong by using the right natural supplement. The mineral zinc, taken as a nasal gel application, appears to markedly shorten the duration of a cold. Zinc lozenges may help too. In addition, a significant body of research suggests that the herb echinacea can also significantly shorten colds as well as make them less severe. The herb andrographis also seems to help.  Vitamin C might also provide some benefit if used properly.

In addition to these substances for treating colds that have already occurred, there are a few treatments that might help prevent colds: andrographis, ginseng, garlic, and a combination product containing echinacea, propolis, and vitamin C.


One famous alternative treatment for colds is the use of zinc in nasal gel or lozenges. When you take zinc this way, you are not using it as a nutrient. Rather, certain forms of zinc release ions that directly inhibit viruses in the nose and throat.

Taking zinc orally as a nutrient might also be useful in some cases. The immune system does not function properly if you don't have enough zinc in your body. 1,2 Because zinc is commonly deficient in the diet, especially among senior citizens,3 nutritional zinc supplementation may certainly be useful for those who get sick easily. Indeed, a 2-year, double-blind study suggests that zinc and selenium taken together in nutritional doses can reduce the number of infections in nursing home residents.4 Ten other studies performed in third world countries have found that zinc supplements at nutritional doses can increase resistance to infection.5,6 However, more isn't better; once you do have enough zinc, getting extra won't help, and might even hurt.

What Is the Scientific Evidence for Zinc Nasal Gel and Lozenges?

In a double-blind, placebo-controlled trial, 213 individuals with a newly starting cold used one squirt of zinc gluconate gel or placebo gel in each nostril every 4 hours while awake. 7 The results were significant: treated participants stayed sick an average of 2.3 days, while those receiving placebo were sick for an average of 9 days, a 75% reduction in the duration of symptoms.

Somewhat more modest but still significant relative benefits were seen with zinc nasal gel in a double-blind, placebo-controlled study of 80 people with colds. 103

However, a slightly larger study of a similar zinc gluconate nasal gel found no benefit. 113 However, this study has been criticized on the basis of the statistical methods used; 114 in addition, it involved artificial infections with cold viruses rather than a natural cold.

A fourth double-blind, placebo-controlled trial, enrolling 185 individuals, also found no benefit with zinc nasal spray. 89 However, this study used a much lower amount of zinc per application than was used in the other studies of nasal gel: 50 times lower. In addition, the spray contained zinc sulfate rather than zinc gluconate. As noted below, the exact chemical form of zinc appears to markedly influence its ability to kill cold viruses, and of these two forms only zinc gluconate is thought to be effective.

Zinc lozenges also appear to be helpful. For example, in a double-blind trial, 100 people who were experiencing the early symptoms of a cold were given a lozenge that either contained 13.3 mg of zinc from zinc gluconate or was a placebo. 8 Participants took the lozenges several times daily until their cold symptoms subsided. The results were impressive. Coughing disappeared within 2.2 days in the treated group versus 4 days in the placebo group. Sore throat disappeared after 1 day versus 3 days in the placebo group, nasal drainage in 4 days (versus 7 days), and headache in 2 days (versus 3 days).

Positive results have also been seen in double-blind studies of zinc acetate. 9,10

Not all studies have shown such positive results. 11 However, the overall results appear to be favorable. 12 It has been suggested that the exact formulation of the zinc lozenge plays a significant role. Flavoring agents, such as citric acid and tartaric acid, appear to prevent zinc from inhibiting viruses, and chemical forms of zinc other than zinc gluconate or zinc acetate may not work; in particular, zinc sulfate may be ineffective. 13 Sweeteners such as sorbitol, sucrose, dextrose, and mannitol are fine, but the information on glycine as a flavoring agent is equivocal.


Until the 1930s, echinacea was the number one cold and flu remedy in the United States. It lost its popularity with the arrival of sulfa antibiotics. Ironically, sulfa antibiotics are as ineffective against colds as any other antibiotic, while echinacea does seem to be at least somewhat helpful. In Germany, echinacea remains the main remedy for minor respiratory infections.

Echinacea is generally said to work by temporarily stimulating the immune system, although recent evidence has tended to cast doubt on this belief. 104,105 Contrary to popular belief, however, there is little reason to believe that echinacea strengthens or "nourishes" the immune system when taken over the long term.

There are three main species of echinacea: Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida. A mixture containing all the parts of E purpurea above the ground (flowers, leaves, stems) has the best supporting evidence for effectiveness in treating colds and flus; the root of E. purpurea is probably not effective, while the root of E. pallida may be the active part of that species.

Echinacea has shown promise for reducing the symptoms and duration of colds and aborting a cold once it has started. However, echinacea does not appear to be helpful for preventing colds. It may also not be effective in children.

Reducing the Symptoms and Duration of Colds

Double-blind, placebo-controlled studies enrolling a total of almost 1,000 people have found that various forms and species of echinacea can reduce the symptoms and duration of a common cold, at least in adults. 14-21,115

For example, in one double-blind, placebo-controlled trial, 80 individuals with early cold symptoms were given either E. purpurea extract or placebo. 22 The results showed that individuals who were given echinacea recovered significantly more quickly: in just 6 days among the echinacea group versus 9 days among the placebo group.

Another double-blind, placebo-controlled trial looked at reduction of the severity of cold symptoms. 23 The results in 246 participants showed that treatment with E. purpurea significantly improved cold symptoms such as runny nose, sore throat, sneezing, and fatigue. Symptom reduction with E. purpurea was also seen in a double-blind, placebo-controlled study of 282 people. 115

In addition, two double-blind, placebo-controlled studies enrolling a total of more than 350 participants found similar benefits with a combination product containing E. purpurea and E. pallida root, along with wild indigo and white pine. 106,107

While the above evidence tends to suggest that the above-ground portion of E. purpurea is active against the common cold, two studies have failed to find benefit. One of these was a double-blind, placebo-controlled study enrolling 120 adults, 116 the other an even larger trial (407 participants) involving children. 117 The reason for these negative outcomes is not clear. Aborting a Cold

A double-blind study suggests that echinacea can not only make colds shorter and less severe, it might also be able to stop a cold that is just starting. 24 In this study, 120 people were given E. purpurea or a placebo as soon as they started showing signs of getting a cold.

Participants took either echinacea or placebo at a dosage of 20 drops every 2 hours for 1 day, then 20 drops 3 times a day for a total of up to 10 days of treatment. The results were promising. Fewer people in the echinacea group felt that their initial symptoms actually developed into "real" colds (40% of those taking echinacea versus 60% taking the placebo actually became ill). Also, among those who did come down with "real" colds, improvement in the symptoms started sooner in the echinacea group (4 days instead of 8 days). Both of these results were statistically significant. 

Preventing Colds

Several studies have attempted to discover whether the daily use of echinacea can prevent colds from even starting, but the results have not been promising.

In one double-blind, placebo-controlled trial, 302 healthy volunteers were given an alcohol tincture containing either E. purpurea root, E. angustifolia root, or placebo for 12 weeks. 25 The results showed that E. purpurea was associated with perhaps a 20% decrease in the number of people who got sick, and E. angustifolia with a 10% decrease. However, the difference was not statistically significant. This means that the benefit, if any, was so small that it could have been due to chance alone.

Another double-blind, placebo-controlled study enrolled 109 individuals with a history of four or more colds during the previous year, and gave them either E. purpurea juice or placebo for a period of 8 weeks. 26 No benefits were seen in the frequency, duration, or severity of colds. (Note: this paper is actually a more detailed look at a 1992 study widely misreported as providing evidence of benefit. 27)

Three other studies also failed to find statistically significant preventive effects. 90,91,118

A study often cited as evidence that echinacea can prevent colds actually found no benefit in the 609 participants taken a whole. 92 Only by looking at subgroups of participants (a statistically questionable procedure) could researchers find any evidence of benefit, and it was still slight.

However, a recent study using a combination product containing echinacea, propolis, and vitamin C did find preventive benefits. 119 In this double-blind, placebo-controlled study, 430 children age 1 to 5 years were given either the combination or placebo for 3 months during the winter. The results showed a statistically significant reduction in frequency of respiratory infections. It is not clear which of the components of this mixture was responsible for the apparent benefits seen.


Andrographis is a shrub found throughout India and other Asian countries, sometimes called "Indian echinacea" because it is believed to provide much the same benefits. It has been used historically in epidemics, including the Indian flu epidemic in 1919, during which andrographis was credited with stopping the spread of the disease. 36 Recently, it has become popular in Scandinavia as a treatment for colds.

Although we don't know how andrographis might work for colds, some evidence suggests that it might stimulate immunity. 37 Interestingly, the ingredient of andrographis used for standardization purposes, andrographolide, does not appear to affect the immune system as much as the whole plant extract.

According to a few well-designed studies, andrographis can reduce the symptoms of colds. It may offer the additional useful benefit of helping to prevent colds.

Reducing Cold Symptoms

A total of seven double-blind, placebo-controlled studies enrolling a total of about 900 people have found that andrographis (or a combination containing it as the presumed primary ingredient) significantly reduces the duration and severity of cold symptoms. 38-40,120

For example, a 4-day, double-blind, placebo-controlled trial of 158 adults with colds found that treatment with andrographis significantly reduced cold symptoms. 41 Participants were given either placebo or 1,200 mg daily of an andrographis extract standardized to contain 5% andrographolide. The results showed that by day 2 of treatment, and even more by day 4, individuals given the actual treatment experienced significant improvements in symptoms as compared to participants in the placebo group. The greatest response was seen in earache, sleeplessness, nasal drainage, and sore throat, but other cold symptoms improved as well.

Three other double-blind, placebo-controlled studies, enrolling a total of about 400 people, evaluated an herbal combination treatment containing both andrographis and Eleutherococcus senticosus. 42,108 One study suggests that this combination may be more effective than echinacea. 121

The same combination has also shown promise in two double-blind studies for reducing the duration, severity, and rate of complications of influenza. 122

Andrographis has also been compared to acetaminophen (Tylenol). In a double-blind study of 152 adults with sore throat and fever, participants received andrographis (in doses of 3 or 6 g per day for 7 days) or acetaminophen. 43 The higher dose of andrographis (6 g) decreased symptoms of fever and throat pain to about the same extent as acetaminophen, but the lower dose of andrographis (3 g) was not as effective. There were no significant side effects in either group.

Preventing Colds

According to one double-blind, placebo-controlled study, andrographis may increase resistance to colds. 44 A total of 107 students, all 18 years old, participated in this 3-month trial that used a dried extract of andrographis. Fifty-four of the participants took two 100-mg tablets standardized to 5.6% andrographolide daily—considerably less than the 1,200 to 6,000 mg per day that has been used in studies on treatment of colds. The other 53 students were given placebo tablets with a coating identical to the treatment. Then, once a week throughout the study, a clinician evaluated all the participants for cold symptoms.

By the end of the trial, only 16 people in the group using andrographis had experienced colds, compared to 33 of the placebo-group participants. This difference was statistically significant, indicating that andrographis reduces the risk of catching a cold by a factor of two as compared to placebo.

Vitamin C

Vitamin C may mildly reduce symptoms of colds when they occur, but it probably does help prevent colds.

Treating Colds

Numerous studies have found that vitamin C supplements taken at a dose of 1,000 mg or more daily can modestly reduce symptoms of colds and help you get over a cold faster. 50,51,100 In addition, one study suggests that vitamin C can enhance the effect of standard cold treatments, such as acetaminophen. 109

Note: In most of these studies, participants used vitamin C throughout the cold season, and found that when they developed colds, the colds were less severe. (This method of using vitamin C does not, however, appear to help prevent colds. See below.) Many people use vitamin C for colds in a different way: they only begin taking it when cold symptoms start. Relatively few studies have evaluated this approach. 53,109   Preventing Colds

Although one recent study suggests that regular use of vitamin C throughout the cold season can help prevent colds, 100 most other studies have found little to no benefit along these lines. 99 Vitamin C has shown a bit more promise for prevention of one type of cold, the “post-marathon sniffle.” These are colds that develop after endurance exercise; use of vitamin C before and during competition may help keep you cold-free afterwards. 54,55 In addition, vitamin C seems to help prevent respiratory infections among individuals who are actually deficient in the vitamin. 56


Although most people in the West think of ginseng as a stimulant, in Eastern Europe ginseng is widely believed to improve overall immunity to illness. As we have seen, echinacea does not seem to prevent respiratory infections. But it appears that regular use of ginseng might be able to provide this important benefit.

There are actually three different herbs commonly called ginseng: Asian or Korean ginseng (Panax ginseng), American ginseng (Panax quinquefolius), and Siberian "ginseng" (Eleutherococcus senticosus). The latter herb is actually not ginseng at all, but some herbalists believe that it functions identically.

A double-blind, placebo-controlled study looked at the potential immune-stimulating effects of Panax ginseng. 57 This trial enrolled 227 individuals at three medical offices in Milan, Italy. Half were given ginseng at a dose of 100 mg daily, and the other half took placebo. Four weeks into the study, all participants received influenza vaccine.

The results showed a significant decline in the frequency of colds and flus in the treated group compared to the placebo group (15 versus 42 cases). Also, antibody measurements in response to the vaccination rose higher in the treated group than in the placebo group.

In addition, two other double-blind, placebo-controlled studies found some evidence that American ginseng may be able to prevent flu-like illness in seniors. 123 In these trials, enrolling a total of about 100 people, use of American ginseng reduced the number of viral respiratory infections (technically, either influenza virus or RSV infection) by about 90%.


The herb garlic has a long history of use for treating or preventing colds. However, up until 2001, there was no scientific evidence that it actually works for this purpose. In fact, many people joked that garlic merely makes you smell so bad people stay away from you, and so you don't catch their cold.

However, there is now some evidence that garlic may really work.

In one 12-week, double-blind, placebo-controlled trial, 146 individuals received either placebo or a garlic extract between November and February. 96

The results showed that participants receiving garlic were almost two-thirds less likely to catch cold than those receiving placebo. Furthermore, participants who did catch cold recovered about one day faster in the garlic group as compared to the placebo group.

Benefits were also seen in a smaller double-blind study. 124

Note that these studies do not indicate that taking garlic will help once you already have a cold.

Essential Oil Monoterpenes: May Reduce Symptoms

Eucalyptus is a standard ingredient in cough drops and in oils meant to be added to humidifiers. A standardized combination of three essential oils, including oils derived from eucalyptus, has been tested for its usefulness in respiratory conditions. The studied combination includes cineole from eucalyptus, d-limonene from citrus fruit, and alpha-pinene from pine. Numerous double-blind trials have found them effective for sinus infections, acute bronchitis, chronic bronchitis, and other respiratory conditions, in both adults and children. 68–72,101 These oils are all in a chemical family called monoterpenes.

In studies, this essential oil combination was taken at a dose of 300 mg 3 to 4 times daily. Other than minor gastrointestinal complaints, no side effects have been reported with this essential oil combination. However, be advised that essential oils can be toxic if taken to excess. Maximum safe doses in young children, women who are pregnant or nursing, and individuals with severe liver or kidney disease have not been established.

Other Proposed Natural Treatments

Various other natural treatments have shown some promise for preventing or treating colds and flus.

Preventing Respiratory Infections

Use of multivitamin/multimineral supplements, or supplements containing zinc and selenium alone, may help prevent respiratory infections in elderly individuals. 4,93,98,125 However, serious concerns have been raised that one of the researchers involved in studying this topic might have engaged in questionable scientific practices.

A 7-month, double-blind, placebo-controlled study of 571 children in day care centers in Finland found that use of milk fortified with the probiotic bacteria Lactobacillus GG modestly reduced the number and severity of respiratory infections. 73

One small double-blind study suggests that the supplement arginine might also be helpful for preventing colds in children. 77

There is some evidence that the supplement glutamine may, like vitamin C, help prevent post-exercise infections. 78–83 For example, a double-blind, placebo-controlled study evaluated the benefits of supplemental glutamine (5 g) taken at the end of exercise in 151 endurance athletes. 84 The result showed a significant decrease in infections among treated athletes. Only 19% of the athletes taking glutamine got sick, as compared to 51% of those on placebo.

In contrast, some evidence suggests that a combination of vitamin E and beta-carotene treatment might increase risk of exercise-associated colds. 126

The thymus gland plays a role in immunity. A 1-year, double-blind, placebo-controlled trial of 16 children with frequent respiratory infections found that treatment with thymus extract could reduce the rate of infection. 85 However, a double-blind, placebo-controlled trial of 60 athletes failed to find any significant evidence of benefit with thymus extract for preventing post-exercise infections. 86

One study widely reported as showing that the supplement colostrum can help prevent colds was actually far too preliminary to prove anything at all. 127

There is some evidence that elements in kelp might help to prevent infection with several kinds of viruses, including influenza. 87 However, the evidence thus far is more theoretical than practical.

Various herbs are said to enhance immunity over the long term, including ashwagandha, astragalus, garlic, maitake, reishi, and suma. However, there is as yet no meaningful evidence that they really work. In addition, several herbs, including ginger, kudzu, osha, and yarrow, are said to help avert colds when taken at the first sign of infection; but again, there is no scientific evidence that they are effective.

Products containing colloidal silver are sometimes used in the belief that they will prevent colds and otherwise strengthen the immune system; however, because colloidal silver can cause permanent color changes in the skin, we recommend that you do not use it. 88

One study in seniors found that use of vitamin E did not help prevent respiratory infections and even somewhat increased the severity of infections that did occur. 102

Some seniors do not respond fully to the influenza vaccine. There is some evidence that vitamin E supplements may strengthen the immune response to vaccinations. 74 Similarly, evidence from two double-blind trials, 93,94 but not a third, 102 suggests that combined multivitamin/multimineral supplements may improve their response. However, in another trial, a multivitamin tablet without minerals actually worsened participants' response to the vaccine. 95

Two studies suggest that combined multivitamin/multimineral supplements can also improve immune response to the vaccine. 93,94 However, two others failed to find benefit, 102,128 and in one study a multivitamin tablet without minerals actually worsened participants' responses to the vaccine. 95 The reason for these discrepancies is unclear; however, serious concerns have been raised that one of the scientists who reported benefits in some of these trials engaged in questionable scientific practices.

In a double-blind, placebo-controlled study of 124 people, the supplement chlorella at a dose of 200 mg or 400 mg daily failed to enhance response to influenza vaccine. 129

Treatment of Respiratory Infections

A standardized product containing elderberry combined with small amounts of echinacea and bee propolis has been widely marketed as a cold and flu remedy. Weak evidence suggests that this mixture may stimulate the immune system and also inhibit viral growth. 75 In a preliminary double-blind study, the combination significantly reduced the recovery time from epidemic influenza B (a relatively mild form of influenza). 76 Another small double-blind study found similar benefits in both influenza A and B. 130

Inhaled essential oils have shown a slight bit of promise for the treatment of colds. 110

Other herbs sometimes recommended to reduce cold symptoms, but that lack supporting scientific evidence, include marshmallow, mullein, and peppermint.

Homeopathic approaches to colds and flus are also discussed in the homeopathy database, in two separate chapters titled, respectively, influenza and common cold.

References. . .

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