Primary prevention
Spread to others may be limited by physical measures including hand-washing, covering the mouth and nose when sneezing or coughing, efficient disposal of tissues carrying nasal secretions, and staying away from work or school. There is no evidence to support use of facemasks.[15][16][17][18]
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Supplements
Vitamin C: vitamin C supplementation has been found to have no benefit in preventing colds.[19][20]
Vitamin D: vitamin D deficiency may be associated with a longer duration of acute respiratory infection, but its effect on the incidence and its severity among healthy adults remains inconclusive.[21] Studies have found that vitamin D3 supplementation does not prevent upper respiratory tract infection in children or adults, even at high doses.[22][23]
Zinc: no firm recommendations can be made with regard to prophylactic zinc supplementation because of insufficient data. Zinc supplementation was shown to prevent up to half of common cold episodes in healthy children <10 years of age. However, such efficacy was not observed in healthy adults, even when a higher dose was used.[24] Oral zinc supplements may be useful for children in regions (such as in developing countries) where there is known to be a high prevalence of zinc deficiency.[25]
Echinacea: the evidence for prophylactic echinacea is inconclusive.[26]
Secondary prevention
Contact with nasal mucus or phlegm coughed up by people with the common cold should be avoided. Hands should be washed before eating or before touching nasal, eye, or oral regions. Avoiding others with a cold, especially during the first few days of illness, reduces the chance of contagious spread.[15]
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