Its diagnosis is based on the pruritic (itchy) papulopustules found in a follicular pattern in these regions.

[3] Pustules are caused by an overgrowth of the yeast Malassezia furfur (formerly Pityrosporum ovale), which plugs the follicles.

This yeast is lipophilic, requiring fatty acids that are present in oily skin to proliferate.

It has been shown that Malassezia yeast grows by consuming fatty acids with carbon chain lengths C11 to C24.

[3] Overgrowth is associated with oily skin, humidity or other pre-existing dermatologic conditions such as seborrheic dermatitis and severe dandruff.