An analysis of 13 placebo-controlled studies showed that zinc lozenges can shorten the duration and decrease the symptoms of the common cold, including pharyngitis. A 40% reduction in the duration of symptoms was noted by combining the studies. The key is to take adequate doses. 75 mg of zinc acetate was needed for maximum effect. Occasionally, the zinc had to be discontinued due to constipation or a bad taste, but other side effects for short-term use were uncommon. Long-term use is not recommended. A deficiency in copper can result.
See Open Respiratory Medicine Journal(click here), 2011;5:51-58.