Olivia, aged 10, attends with her parents for follow-up of tinea pedis, which developed after a recent school camp. The foot rash has resolved, but a new perioral erythematous rash has now appeared.

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Professor Dedee Murrell is head of dermatology at St George Hospital and conjoint professor at the University of NSW.

This article is co-authored by Dr Timothy Cowan, a dermatology registrar at St George Hospital, and Henry Lee, a medical student at the University of NSW.