Zinc for the Common Cold 

Meenu Singh and Rashmi R Das 

The common cold is one of the most frequent ailments, and it is a primary cause of  medical visits and missed school and work. Since 1984, trials in high-income nations studying  the effect of zinc in the treatment of common cold symptoms have yielded inconsistent findings.  The goal is to see if zinc (regardless of the zinc salt or formulation) is effective in lowering the  occurrence, intensity, and duration of common cold symptoms. In addition, we wanted to see  whether there were any potential causes of heterogeneity in the data and if so, what the clinical  implications were. Zinc given within 24 hours after commencement of symptoms shortens the  length of common cold symptoms in healthy adults, however due to the heterogeneity of the  findings, care is advised. Due to a lack of research, no solid recommendations on preventive zinc  supplementation can be provided at this time. When using zinc lozenges (rather than zinc syrup  or pills), the expected benefit must be weighed against the potential for adverse effects, such as a  poor taste and nausea. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6457799/