Fluorescence Detected in Patients With COVID-19 Treated with Favipiravir

Wood's lamp on an arm
Cropped shot of dermatologist using the Wood Lamp for diagnosis of skin condition
The Wood’s lamp examination findings of patients prescribed favipiravir for COVID-19 are reviewed.

Wood’s lamp examinations of patients with COVID-19 treated with favipiravir, a broad-spectrum antiviral that inhibits viral RNA polymerase activity, revealed a fluorescent appearance in their hair and nails, according findings in a letter to the editor published in Dermatologic Therapy describing a study of a small patient cohort.

The study authors of the letter provided pictures of Wood’s lamp results of the hair and nails of 7 patients, 4 men and 3 women, treated with oral favipiravir (6-fluoro-3-hydroxy-2-pyrazine caboxsamide). Patients were treated with 1,600 mg twice a day on the first day, followed by 600 mg twice a day until day 5, reaching a total dose of 8,000 mg of favipiravir.

Patients experienced green and white fluorescence in their nails and green fluorescence in their hairs. Investigators sampled the distal part of patient 3’s fingernail and could not detect favipiravir on toxicological examination.

The study was limited by the inability to detect a possible relationship between the cumulative dose/duration of therapy and the degree of fluorescence seen, as well as the lack of paired hair and nail samples for toxicological analysis.

“Since favipiravir is thought to be phototoxic, it may be necessary to avoid UV exposure during the period until the drug is eliminated from the body,” the letter authors wrote.


Demir B, Cicek D, Turkoglu S, Bozdemir NY, Sarikurt F, Banoglu E. Wood’s lamp examination of hair and nails related to COVID-19 treatment. Dermatol Ther. Published online October 24, 2021. doi:10.1111/dth.15174