Fluorescence in the Sclera, Nails, and Teeth Secondary to Favipiravir Use for COVID-19 Infections.

Favipiravir, an antiviral agent originally used for influenza infections, has become popular due to its beneficial signals in coronavirus disease. It is currently used in some countries within COVID-19 treatment protocols. This is an initial report of favipiravir-related fluorescence observed in three healthcare providers working in the same ward in our hospital. All three individuals had been diagnosed with COVID-19 two months earlier and were treated with favipiravir. None of the three individuals received hydroxychloroquine or tetracyclines. Wood's light examination led to an incidental discovery of favipiravir-induced fluorescence involving the sclera, nails, and teeth. In all patients, white linear, square, and band-like specks of fluorescence were noticed on the sclera of both eyes, some teeth, and the proximal part of all fingernails and toenails. Exposure of the eyes to the Wood's light was for a brief duration of 3 to 5 seconds during examination and photodocumentation. Favipiravir might cause bright white fluorescence of nails, sclera, and teeth, detectable by Wood's light even two months after its cessation.