Our clinically tested formula releases zinc ions in the mouth and shortens the duration of the common cold. Take Cold-Eeze at the first sign of a cold. Clinically tested to shorten colds by 42% (A clinical study found the Cold-Eeze formula reduces the duration of the common cold by 42%, when taken at the first sign of symptoms and used as directed). The double blind placebo controlled study was conducted at the Cleveland Clinic and published in a peer reviewed journal.