Skin fungus

Skin mycoses are infections caused by microscopic fungi that feed on the keratin of the most superficial layer. They are not a matter of hygiene — that is the misconception that does most harm — but of environment: heat, moisture and macerated skin are the conditions that favour them, which is why they appear in the folds, under the breasts, in the groin, between the toes.

The typical shape helps recognition: a rounded patch spreading from the periphery, with a red, scaling edge and a centre that tends to clear. This is why it is called ringworm: it looks like a ring. Itching is almost always present, but it is not the orienting sign.

What really changes matters is something else, worth knowing before buying anything at the pharmacy. A corticosteroid cream on a mycosis makes it look better and makes it worse. The steroid quells the redness and the itch, so the patient is convinced it is working, but it removes the brake on fungal growth: the patch spreads and loses its typical appearance, becoming much harder to recognise. This picture has a name — tinea incognita — and it reaches the clinic weeks late.