Natural medicines for the common cold

Along with the colder weather comes cold and flu season. While basic measures such as frequently washing hands and sleeping at least eight hours each night may reduce the risk of contracting a cold, several natural medicines (vitamin C, zinc lozenges, echinacea, green tea, Airborne, etc.)  are widely touted to provide benefits … but, do they?

In the United States, most colds occur during the fall and winter. Beginning in late August or early September, the rate of colds increases slowly over a few weeks and remains high until March or April, when it declines. The seasonal variation may relate to the opening of schools and to cold weather, which prompt people to spend more time indoors and increase the chances that viruses will spread from person to person.

Here is a synopsis of the most up-to-date information on four of the more popular natural medicine treatment of the common cold from the experts at the Natural Standard (NS) and the Natural Medicines Comprehensive Database (NMCD):

Vitamin C:

According to the NMCD:

There is a lot of controversy about the effectiveness of vitamin C for treating the common cold. The majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patient). However, other studies have found no effect with doses up to 3 grams daily.

Some research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. There may also be a dose-dependent response; doses of at least 2 grams per day seem to work better than 1 gram doses.

Tell patients that the high doses used for treating the common cold, 1-3 grams daily, can increase the risk of side effects. Some patients might not think the modest benefit is worth the risk. Explain to patients that taking vitamin C supplements prophylactically does not decrease the risk of catching a cold.

Dietary intake of vitamin C also doesn’t seem to affect the risk of getting a cold.


According to the NS:

Available studies report conflicting results on the impact of zinc on the common cold. Overall, studies suggest that if taken when symptoms begin, zinc may help treat cold symptoms. Effects are strongest in adults. Zinc gluconate is not recommended for sore throats. Further research is needed to clarify which zinc formulas are effective for reducing symptoms. More studies are needed before a firm conclusion may be drawn.

According to the NMCD:

There’s also no reliable evidence that taking zinc supplements can help PREVENT a cold and research is divided on zinc for treating colds.

A lot of research suggests that zinc lozenges providing 9-24 mg elemental zinc per dose started within 24-48 hours of the onset of cold symptoms reduces the severity and duration of colds in adults. The majority of studies use zinc gluconate or acetate lozenges. Lozenges should be taken every 2 hours while awake, starting within 48 hours of symptom onset. But other research shows no effect.

Tell patients who want to try zinc lozenges that they’ll need to take a zinc lozenge every 2-3 hours while awake. Explain that zinc can produce a dry or astringent feeling in the mouth.

Overall, zinc products seem to be beneficial for reducing the duration of symptoms of the common cold in adults by about 1.6 days, but adverse effects such as bad taste and nausea may limit their usefulness.

There is also conflicting evidence on zinc nasal sprays such as Zicam Cold Remedy Nasal Gel. There is concern about side effects related to zinc nasal sprays. Case reports and animal research has linked intranasal zinc to permanent anosmia (loss of sense of smell) in rare instances. In 2009, Zicam nasal sprays were removed from the market in the U.S. due to over 130 reports of loss of smell. Advise patients not to use these products.

Green tea:

According to the NS:

Green tea is made from the dried leaves of Camellia sinensis, an evergreen shrub. Polyphenols, compounds found in green tea, have been shown to have antiviral effects. Early research suggests that specific green tea formulas may help prevent cold and flu symptoms. In children, drinking one to five cups daily has been linked to a reduced risk of developing the flu. More studies are needed to confirm these results.

According to the NMCD:

There is insufficient evidence for using green tea to prevent or treat the common cold.


According to the NMCD:

Teas are often promoted for cold and flu symptoms. Elderflower, rose hip, goldenseal, chamomile, peppermint, slippery elm, ginger, Mormon tea, linden flowers, meadowsweet, and other herbs are used. The hot liquid may be soothing, but there’s no reliable evidence for efficacy. In fact, research suggests hot humidified air doesn’t affect cold symptoms.


According to the NMCD:

 A lot of people are using the product Airborne. Promotional material says that it was “developed by a school teacher who was sick of catching colds in class.” But there is nothing much different about this product and many others promoted for preventing colds. It contains vitamin C, vitamin E, vitamin A, zinc, echinacea, and other ingredients. But there is no reliable evidence that it can prevent or treat a cold. Don’t recommend it.


According to the NS:

Echinacea species belong to the aster family (Asteraceae) that originated in eastern North America. Of the nine identified species, only three are used as medicine. The roots and herbs of the species have been studied for potential immune benefits.

Taking echinacea by mouth is often suggested as a treatment for the common cold. Echinacea may help reduce the length and severity of the common cold. Much research has focused on the potential benefits of echinacea for this purpose. Although most studies report positive effects, some recent high-quality trials found negative results in adults and children. More research is needed before a firm conclusion can be made.

According to the NMCD:

Echinacea is widely used to prevent upper respiratory infections including colds and flu. Echinacea has been studied for prophylaxis against the common cold, but has consistently been shown to be ineffective for this use. Don’t recommend echinacea for PREVENTING colds and flu.

There is controversy about how well echinacea might work for treating colds due to conflicting evidence. Taking some echinacea preparations seems to modestly reduce symptom severity and duration, possibly by about 10% to 30%. But some studies show no benefit.

As a whole, the best evidence appears to be for preparations of the Echinacea purpurea species. If a patient decides to try echinacea, suggest preparations using this species.

Tell patients with ragweed allergies NOT to use echinacea. Echinacea is in the same plant family as ragweed and might have cross-allergenicity.


According to the NS:

Goldenseal is one of the five top-selling herbal products in the United States. Studies on the effectiveness of goldenseal are limited to one of its main chemical ingredients, berberine salts. A small amount of berberine is actually present in most goldenseal preparations.

Goldenseal has become a popular treatment for the common cold and upper respiratory tract infections, and is often added to echinacea in commercial herbal cold remedies. Berberine may have 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.

According to the NMCD:

Lots of natural products are tried for treating a cold or flu … goldenseal (is) , pau d’arco, astragalus, larch arabinogalactan, bee propolis, boneset, wild indigo, and Siberian ginseng. These products are often marketed as “immune system supporters.” They are used alone or in combination with other natural products, such as echinacea. But there’s no reliable clinical evidence that they relieve cold symptoms.


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