Prevention

Because colds and flus are easily spread, everyone should always wash his or her hands before eating and after going outside. Ordinary soap is sufficient. Waterless hand cleaners that contain an alcohol-based gel are also effective for every day use and may even kill cold viruses. (They are less effective, however, if extreme hygiene is required. In such cases, alcohol-based rinses are needed.)

Antibacterial Products

Antibacterial soaps add little protection, particularly against viruses. In fact, one study suggests that common liquid dish washing soaps are up to 100 times more effective than antibacterial soaps in killing respiratory syncytial virus (RSV), which is known to cause pneumonia. Wiping surfaces with a solution that contains one part bleach to 10 parts water is very effective in killing viruses.

Temperature

Colds are not caused by insufficiently warm clothes or by going outside with wet hair. A 2002 study reported, however, that in older adults cold temperatures can thicken the blood and may increase the risk for respiratory infections and even circulatory and heart problems. (This danger does not appear to affect people under 55 years of age.)

Dietary Factors

Foods Containing Lactobacilli (Good Bacteria). Researchers are also studying the possible protective value of certain strains of lactobacilli bacteria found in the intestines. Some of these strains, particularly acidophilus, are used to make yogurt. According to one Finnish study, children attending day care who ate milk containing the strain lactobacilli GG 10 - 20% fewer respiratory infections. (The strain used was not the kind found in most commercial yogurt products.)

Vitamins. Studies are mixed whether vitamin supplements protect against upper respiratory infections. Large doses of vitamin C, for example, may help reduce the duration of a cold, but they do not appear to protect against one in the first place, even after exposure to a cold virus. Two studies in 2002 on multivitamins reported opposite results, with one finding fewer infections and one finding no difference. It is possible that vitamin C or multivitamin supplements may be helpful in specific people, such those who are vitamin deficient or have medical problems that impair their immune systems.

Studies on vitamin E specifically have been largely negative. A 2002 study, in fact, reported a higher incidence and greater severity of respiratory infections in older adults who took 200 mg of vitamin E daily.

In contrast, a 2006 study conducted in Japan found people who took 500 mg of vitamin C daily had fewer colds than people who took 50 mg of the vitamin. Vitamin supplementation, however, had no apparent effect on the duration of the cold or severity of symptoms, the study noted.

Factors Associated with a Lower Risk for Respiratory Infections

Breastfeeding. Some evidence suggests that women who breastfeed reduce the risk of respiratory infections in their children. Low Stress and Active Social Life. More than one study has reported that people with low stress who also have an active social life have fewer colds than people who have high stress levels or those who have low stress and few social connections.

Review Date: 12/21/2006
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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