Definition

Seborrhoeic dermatitis is a common non-contagious skin condition affecting millions of people. It is a papulosquamous disorder that affects the sebum-rich areas of the scalp, face and trunk.

Its exact cause is unknown, though cases are often attributed to the overproduction of sebum in the sebaceous glands, the presence of topical organisms such as Malassezia yeasts (formerly known as pityrosporum ovale) and inflammatory or immunologic abnormalities.

Patients with a compromised immune system (such as sufferers of HIV/AIDS) are typically susceptible to more frequent and severe cases of seborrhoeic dermatitis, while neurological conditions such as Parkinson's disease are also understood to induce a higher prevalence. Other factors which may trigger outbreaks include physical trauma (eg scratching), seasonality or emotional stress.

Symptoms

Manifestations of SD skin lesions include:

  • Patchy scaling or thick crusts on the scalp
  • Yellow or white scales that attach to the hair shaft
  • Red, greasy skin covered with flaky white or yellow scales
  • Itching or soreness
  • Skin flakes or dandruff

Hypopigmentation may occur in black patients.

Sebclair

Affected areas

SD occurs on the more oily areas, or where there is a certain amount of hair, such as the scalp, forehead, eyebrows, eyelash line, nasolabial folds, beard and postauricular skin. It may also be present on the skin under the chin.

Chronic disease

SD is characterised by intermittent periods of remission, followed by periods of exacerbation, when patients experience the burning, scaling and itching symptoms associated with the condition. Flare-ups tend to be more common in winter and early spring, with periods of remission usually occurring in summer.

Epidemiology

The global prevalence rate of seborrhoeic dermatitis is 3-5%. Dandruff, the mildest form of SD, is far more common and affects an estimated 15-20% of the population.

Race

Seborrhoeic dermatitis may affect people of all races and ethnic groups.

Sex

Seborrhoeic dermatitis is slightly more prevalent in men than in women.

Age

SD usually occurs with puberty. It peaks at around age 40 and is less severe, but present, among older people. In infants, it occurs as cradle cap or, less frequently, as a flexural eruption or erythroderma.

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