Medical Health Encyclopedia

Zinc appears to have certain important effects on the immune system and it may have a direct effect on viruses. How it works is not entirely clear, however. Zinc preparations in lozenge or nasal gel form are now available as cold treatments. Studies are very mixed on the effects of zinc on colds. The variance may be due to different zinc preparations. Studies are underway to determine advantages, if any. Some examples include the following:

• A nasal gel (Zicam), which contains zinc gluconate, has shown some success, possibly because the gel sticks to the nasal passages long enough for the zinc to interact with the virus. In a 2003 study, for example, the nasal gel shortened the duration and severity of the cold compared to placebo when it was started within 14 to 48 hours of the onset of symptoms. The supports earlier studies reporting that it shortened the duration of a cold by about two days.
• Zinc lozenges are showing mixed results. One 2000 study suggested that the use of zinc acetate lozenges (e.g., Fast-Dry, Galzin) may be more effective and have a better taste than other formulations, such as zinc gluconate (Cold-Eeze, Orazinc). On the other hand, a 2002 study reported that zinc gluconate reduced cold duration significantly. To further confuse matters, the two zinc lozenge preparations were directly compared in a 2000 study, and neither was effective. The reasons for these conflicting results are not clear.
• A small 2001 study on a nasal spray preparation found no benefits. The spray preparation had less zinc than the nasal gel.

In any case, no one with an adequate diet and a healthy immune system should take zinc for prolonged periods for preventing colds.

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Side Effects. Side effects, particularly of the lozenge form, include the following:

• Dry mouth
• Constipation
• Nausea
• Bad taste (possibly only with zinc gluconate lozenges)
• Severe vomiting, dehydration, and restlessness (signs of overdose, seek medical help)
• Allergic response (rare)