Does zinc actually shorten a cold?

What the evidence says

Zinc is a mineral your body needs for a healthy immune system. Because of this, scientists have tested whether taking extra zinc during a cold, usually as a lozenge that dissolves in your mouth, can make the cold go away faster.

A 2024 Cochrane review, which is a large study that combines results from many trials, looked at this question. It found that zinc might cut a couple of days off how long a cold lasts, but the results were not consistent enough to be certain, and the researchers rated the evidence as inconclusive.

Older reviews, including one published in the Canadian Medical Association Journal, found similar hints that zinc lozenges could shorten colds, especially when started within a day of the first symptom. But trials used different zinc doses and forms, like zinc acetate versus zinc gluconate, and this made it hard to give one clear answer. Some smaller meta-analyses focused only on high-dose zinc acetate lozenges found bigger effects, but these are less certain than a single large, consistent trial would be.

There is also an important safety point. Zinc taken by mouth as lozenges or syrup appears reasonably safe for short-term use, aside from an unpleasant taste or nausea. But zinc nasal sprays or gels are a different story. Several case reports and reviews have linked nasal zinc products to lasting loss of the sense of smell, called anosmia, so these are best avoided even though some oral lozenges are considered lower risk.

Overall, the honest answer is that zinc lozenges might shave a day or two off a cold for some people, but the science is not settled, and it does not seem to stop you from catching a cold in the first place.