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Farmer with rash on left hand
Last reviewed: August 2022
Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief, 2022.
Edited by the DermNet content department
Background
A 50-year-old farmer has developed a rash on the back of his left hand. He initially applied an udder cream that he uses on his dairy cows, but this was unhelpful. He was given a steroid cream by another farmer which is hindering rather than helping.
Where else should you look?
A unilateral, marginated, scaly eruption on the back of the hand is very suggestive of a dermatophyte infection. His interdigital web spaces on the feet and his groin should be checked for clinical evidence of tinea.
What investigation is required?
What is the diagnosis?
This is tinea incognito, a fungal infection that has been modified by the application of topical steroids. They make the eruption spread and very often push the fungus into the follicles producing follicular pustules.
What treatment is needed?
Tinea incognito usually requires an oral antifungal agent such as terbinafine or itraconazole. If the causative fungus has been acquired from an animal, then input from a vet should be sought.