Dandruff on the scalp: what causes it and why it becomes excessive

White flakes on a collar are not noticed right away: first a couple of specks on a dark sweater, then a light trail on the shoulders after combing. Dandruff is not a disease in the strict sense, but a visible outward sign that the scalp is shedding faster than usual. Next — where these flakes come from and why one person has almost none, while another's head looks as if it has been powdered.

What dandruff is

Dandruff (Latin pityriasis — "bran") is a condition in which skin particles shed at a high rate and for a long time. Most often this happens on the scalp under abundant hair.

It is not contagious, and the cause is not poor hygiene: with infrequent washing the flakes are simply more noticeable. White flakes are visible on the hair and fall onto clothing, especially on dark hair. The skin underneath may be dry and itchy.

What causes dandruff: main causes

There are several causes, and usually they act together: excessive sweating, increased sebum production, alkaline detergents, alcohol. Dandruff appears when metabolism is disturbed, causing the sebaceous glands to function incorrectly (seborrhea), with excessive proliferation of fungal microflora — and most often with both at once. Heredity plays a role: the structural features of the skin and its secretion.

Skin diseases can produce a similar picture: seborrheic dermatitis, eczema, psoriasis, contact dermatitis as a reaction to dye, spray or gel, ringworm. Seborrheic dermatitis has its own risk factors:

• stress and fatigue, weather extremes;
• oily skin and skin problems such as acne;
• heavy alcohol use, alcohol-based lotions;
• obesity;
• diseases of the nervous system — Parkinson's disease, brain injury, stroke; HIV/AIDS.

The role of fungus and scalp oiliness

Yeast-like Malassezia fungi live constantly on the skin — where there are many sebaceous glands. With good immunity the fungus does not manifest itself; under heavy mental and physical stress or poor nutrition it becomes active. The composition of sebum also changes: the proportion of free fatty acids in it grows, and the secretion loses its sterilizing properties.

The external picture depends on the ratio of sebum and flakes. In oily liquid seborrhea the skin is greasy, the hair looks as if smeared with oil, sticks together in strands and is densely covered with tightly adhering yellowish flakes. In dry seborrhea there is less sebum secretion, but the flakes cover the skin and hair almost entirely; the hair is dry, thin, brittle.

Why there can be a lot of dandruff and why it can be fine

Normally the cell desquamation cycle takes about a month. When the fungus becomes active, cells divide faster and the cycle takes no more than a week: the cell does not have time to fully dehydrate. The mass of flakes exceeds the usual and becomes visible to the naked eye.

The appearance of the flakes also differs. Fine dry crumbs scattering with every movement are a picture of dry seborrhea. Large yellowish, greasy and sticky flakes that stay near the skin are a sign of the oily form. If itching, irritation and individual patches of redness are added, this is seborrheic dermatitis.

The amount of sebum depends on the state of the endocrine and nervous systems, sex and age. It is produced most during puberty: a predominance of androgens over estrogens is more common between the ages of 14 and 25, and in old age there is noticeably less secretion.

Dandruff in children: how it may differ

In infants, seborrheic dermatitis of the scalp is called cradle cap: greasy yellowish crusts on the head, eyebrows and diaper area. A separate cause of flakes in childhood is ringworm: a red or silvery rash on the scalp, sometimes with patchy hair loss.

When dandruff requires a visit to a dermatologist

The diagnosis is made by the appearance and location of the changes; a skin biopsy is rarely needed. A reason to see a doctor is flaking that persists after four weeks of using an anti-dandruff shampoo, severe dandruff or very intense itching, redness and swelling of the scalp, scaly itchy plaques on the face and body. Separately: if the lesions discharge fluid or pus, become covered with crusts, become very red or painful.

The doctor examines the scalp and looks for skin diseases that may underlie the flakes. Seborrheic dermatitis is chronic, runs in waves, but is controllable; psychological discomfort and secondary infections are possible.

Dandruff by itself is not a reason to call an ambulance. 103/112 — if, simultaneously with changes in the scalp, signs of a life-threatening condition appear: for example, a stroke or heart attack.

This material is for reference: it describes how this usually looks, but does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer