Research zinc lozenges having a positive ZIA value reduced the duration of common colds in a dose-response manner. ZIA 25 lozenges reduced duration of colds by about 1-1/2 day, while lozenges having a ZIA value of 44 reduced the duration of colds by 4.8 days, and lozenges having a ZIA value of 100 reduced the duration of colds by 7 days. Lozenges having a zero ZIA did not have any effect on colds. Zinc lozenges released negatively charged zinc species at physiologic pH (as shown in the lower-left corner of the above figure) and increased the duration and severity of common colds in a dose-response manner. Although we do not know of any commercial zinc lozenges with a negative ZIA value, it is possible that they are on the market.