Dermatitis or seborrhoeic dermatitis of the scalp is an inflammatory skin disease (or dermatosis). It takes the form of oily flakes or dandruff on the scalp, mainly affecting the forehead, around the ears (and sometimes even the nasal concha and external auditory canal), and sometimes the face itself, particularly the forehead and T-zone (eyebrows, nose and nasolabial folds). These areas are generally the richest in sebum and therefore favourable to the proliferation of fungi. In men, the sternum may also be affected.
On light-coloured skin, the patches may be accompanied by redness (the surface of which is a whitish or yellowish colour similar to that of pus) with skin particles that may be detached, while in dark-coloured skin there is often associated depigmentation. In almost all cases, pruritus (itching) is reported.
The diagnosis is clinical, and it is sometimes difficult to distinguish between incipient scalp psoriasis, especially if there is little redness, eczema or ringworm of the scalp. In these cases, the concomitant involvement of other areas of the body, a possible atopic background, the course of the disease and a mycological sample of the scales can help guide the diagnosis.
Seborrhoeic dermatitis is a benign, non-contagious disease, but it is chronic, with recurrent outbreaks. Unsightly and often the cause of embarrassment, its visible lesions can have a detrimental effect on quality of life. It mainly affects men, with six men affected for every woman. It can also affect infants, known as "cradle cap". After the age of 40, the disease is less common and almost exclusively affects men.
