Skin patches after sun exposure

Pityriasis versicolor almost always leaves the same doubt: "I finished the treatment, but the patches are still visible. Does that mean the fungus is still there?" Not necessarily — and it is a distinction worth understanding, because it avoids restarting courses of therapy that are not needed.

The condition is linked to the proliferation of Malassezia yeasts, microorganisms that are a normal part of the skin microbiota. They do not come from outside and are not "caught": what changes is their balance, favoured by heat, humidity and sweating. This is why it typically appears or worsens in the warm months.

During the active phase the patches may show fine superficial scaling, and that is the component that responds first: as proliferation is controlled it tends to resolve. The difference in colour, however, is slower. Malassezia temporarily alters pigmentation in the areas involved, and colour normalisation — especially in the lighter patches — can take weeks or months after the active infection has gone.

The practical consequence is that a residual patch is not proof that treatment failed. Judging by colour alone leads to wrong conclusions: the activity of the condition must be distinguished from the pigmentary outcome. It should also be said that pityriasis versicolor tends to recur, particularly when temperature, humidity and sweating again favour the yeast.