Do zinc lozenges actually work as a cold treatment?

It’s sniffle season. If you have a cold that you can’t kick, you may be researching tips to overcome your infection. After looking into whether vitamin C can stop cold symptoms, we wondered about another commonly promoted cure: zinc. 

Zinc is one of the body’s essential minerals. It’s important for immune system function, wound healing, bone growth, hormone production and our senses of taste and smell. People generally get all the zinc they need from their diet — zinc deficiency is uncommon in the U.S. — but over-the-counter zinc lozenges and nasal sprays are often sold as cold-quashing treatments.

Does it really work? 

A 2024 paper published by the Cochrane Database of Systematic reviews looked at the results of 34 studies on zinc to prevent or treat the common cold. The review’s authors found that when it comes to preventing a cold, there is little to no benefit of regularly taking zinc supplements. 

But zinc shows promise in treating colds.

The Cochrane review found that zinc may reduce the average duration of a cold by around 2.4 days when compared to a placebo. But the authors didn’t give a full-throated endorsement of zinc as a cold cure: They wrote they had “little confidence” in the evidence.

Study results aren’t always consistent. Several experimental studies and meta-analyses have found similar results supporting zinc’s cold-shortening benefits while others haven’t found a significant effect. 

In order for zinc to be even a little effective as a cold treatment, it must be taken as a lozenge or a nasal spray so it can directly affect the nose and throat where respiratory infections take root. But beware — zinc nasal sprays have been linked to permanent loss of smell, leading to FDA warnings about several products.

Dr. Harri Hemilä, a Finnish researcher who has studied how zinc affects colds, told Well Informed that part of the reason study results differ may be because doses and ingredient formulations vary.

Of the 34 studies in the Cochrane review, dosages ranged from 0.044 milligrams to 296 milligrams of zinc per day, and included several types of zinc — zinc acetate, zinc gluconate, and zinc orotate — administered in different forms, such as nasal spray, lozenge, and syrup.

In a 2011 systematic review of 13 studies, Hemilä found that trials using daily doses of less than 75 milligrams lozenges had no effect on cold duration, but those with over 75 milligrams did show a benefit.

“The greatest problem with using zinc lozenges to treat colds is the difficulty in finding proper lozenges,” Hemilä said, noting the ones on the market may be too low of a dose or include ingredients like citric acid that bind to zinc and make a lozenge less effective. 

Common lozenge brands like Cold-EEZE contain around 11-13 milligrams each, meaning a person would need to consume six to seven lozenges a day to surpass that 75 milligram threshold. That may be more than what the package instructs you to take. 

These zinc cold products can cause side effects, most commonly bad taste, nausea, and diarrhea — which people may decide isn’t worth it just to shave a few days off a cold. But in terms of safety,  for a short cold treatment, these higher doses of zinc are unlikely to cause dangerous zinc toxicity. 

“As far as we know, there are no serious risks to taking the lozenges for a few days,” said Dr. Mark H. Ebell, a family medicine professor at Michigan State University.

That doesn’t mean you should be taking this much zinc regularly. The recommended daily intake for adults is 8-11 milligrams, and you shouldn’t take more than 40 milligrams regularly as it can cause dangerous health effects like copper deficiency. 

For someone with a bad cold, it may be worth a try, but don’t expect a miracle. And always talk to your doctor before adding a new supplement to your routine.