People most often take zinc in the form of lozenges to reduce the duration of cold symptoms. Scientific studies are inconsistent, but if zinc has an effect, it probably is small and occurs only when it is taken very soon after cold symptoms develop.
Some people take zinc to slow the progression of age-related macular degeneration, which is an eye disease, or to help heal wounds because zinc deficiency delays wound healing. In developing countries, once weekly supplements containing zinc and iron during the first year of life may decrease mortality due to diarrhea and respiratory infections. In children older than 6 months who are undernourished or who have a zinc deficiency, zinc supplementation may help treat diarrhea.
Zinc may also help decrease blood glucose levels in people with diabetes or pre-diabetes.
Mild zinc deficiency impairs growth in children and can be corrected with zinc supplementation.
Zinc is generally safe, but toxicity can develop if high doses are taken. The common side effects of zinc lozenges include the following:
Because zinc is a trace metal and can remove other necessary metals from the body, intake of zinc lozenges should be limited (for example, to no more than 14 days). Zinc sprays may irritate the nose and throat.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health (NIH), National Center for Complementary and Integrative Health: Information on some complementary health approaches for the common cold, including zinc, vitamin C, echinacea, probiotics, nasal saline irrigation, buckwheat honey, geranium extract, and garlic