What is erythrasma?
Erythrasma is a common skin condition affecting the skin folds such as under the arms, in the groin and between the toes.
Erythrasma does not usually cause any symptoms. It presents as a slowly enlarging area of pink or brown dry skin.
Wood's light fluorescence
What is the cause of erythrasma?
The cause of erythrasma is a bacterial infection. The bacteria responsible for erythrasma are Corynebacterium minutissimum. This may coexist with a dermatophyte fungi or with Candida albicans (thrush).
Erythrasma can be confused with other causes of intertrigo (rashes in the skin folds).
Erythrasma can infect anyone, but is particularly prevalent in those living in a warm climate or who have diabetes.
How is the diagnosis of erythrasma made?
The appearance of erythrasma is often typical. Exposure to longwave ultraviolet radiation (such as with a black light or Wood's light) causes the erythrasma to fluoresce a coral-pink colour due to porphyrins released by the bacteria.
The diagnosis can be confirmed by a swab or scraping for microscopy and culture.
What is the treatment for erythrasma?
Photodynamic therapy using red light (broadband, peak at 635 nm) has also been used to treat patients with erythrasma.