Based on well documented evidence, Matrixx’s Zicam caused anosmia (loss of smell) as a result of a toxic descruction of the olfactory epithelium. The implicated component or ingredient is zinc that, while critical for maintenance of normal smell function through its action as a cofactor in carbonic anhydrase VI, given directly into the nostrils at high concentrations, can initiate direct toxic destruction of the olfactory epithelium. Though these cells have been shown to regenerate in animal studies, the same cannot be said for humans. The symptoms suffered by users include a rapid onset of a burning sensation when the product is sprayed directly into the nasal passage. As a result of this acute toxicity, consumers suffer loss of smell and taste along with a loss of appetite and decrease in quality of life.
Alarmingly, Matrixx notice of this issue can be traced back over a decade but certainly to Dr. Bruce Jafek, a distinguished otolaryngologist in Denver, CO who reported this effect in 2003.