What exactly is dandruff?
Dandruff results from the abnormal proliferation of a micro-organism from the Malassezia family, which is a yeast. This phenomenon causes skin cells in the epidermis to renew much too quickly. They appear in clumps on your scalp, forming large dandruff or patches that fall off or become sticky. They look oily and yellowish-grey.
This can be accompanied by an extremely irritated scalp and intense itching. Dandruff is visible in your hair and, in most cases, falls onto your neck and shoulders, particularly during styling. Fatigue, stress, pollution and the winter are factors that can promote or increase malassezia furfur proliferation and thus the appearance of dandruff.
What are the different types of dandruff?
There are two types: dry dandruff and oily dandruff. The way they look provides information about the root cause of the issue.
. In moderate dandruff cases, scales are thin, dry, grey or whitish and do not stick to the scalp; they fall onto the shoulders.
. Thick, greasy and yellowish dandruff sticks to the scalp and is usually accompanied by itching. It is a minor form of seborrhoeic dermatitis. The scalp is often pink and irritated.
. Dry, whitish patches accompanied by underlying redness are psoriasis characteristics. In this case, itchiness also usually occurs.
If you have concerns about severe dandruff, contact your dermatologist.
What causes severe, chronic scaly patches or psoriasis?
Psoriasis is characterised by severe scales with dry areas that appear as thick, clearly-defined patches - particularly on the edge of the scalp - and are round or oval-shaped, with redness and scales. These scales vary in size and can resemble a helmet covering the whole scalp. They are silvery white, compact, dry and particularly sticky. They are generally accompanied by intense itching.
Genetic predisposition, stress, certain infections (eyes, nose and throat and dental in particular), and the use of certain medicines (lithium, synthetic anti-malarials, beta-blockers, etc.) can play a role in the appearance of severe scales with dry areas.
They result from the combination of 3 phenomena:
. Epidermal cell hyperproliferation, which causes the skin to significantly thicken on the patches, with redness and scales.
. Impaired differentiation, i.e. epidermal cell renewal. This process that usually lasts around 30 days is reduced to less than one week (3 to 6 days). The keratinocytes experience problems differentiating while ageing: they keep their nucleus until reaching the horny layer.
. An inflammatory reaction in the dermis.
Severe scales with dry areas progress in successive phases of flare-ups and remissions.
What makes scales severe?
Scales can be related to two diseases: seborrhoeic dermatitis (SD) and psoriasis.
With SD, scales are caused by the same thing as dandruff (Malassezia yeast proliferation) and have more pronounced clinical signs.
Psoriasis is not caused by a fungal proliferation; rather, it is a completely different condition related to a genetic predisposition brought to light by environmental factors.