SCN9A and Kallmann syndrome: In the current article, we establish a robust correlation between anosmia resulting from methimazole treatment or COVID-19 and a decrease in NaV1.7 expression in the superficial layer of the olfactory epithelium of mice, hamsters, primates, and humans, and we demonstrate the utility of NaV1.7-targeted fluorescent Tsp1a peptides in detecting the changes in NaV1.7 expression in OSNs.