Sebum is the oily substance secreted by sebaceous glands in the skin. This oil on the skin has the protective function of keeping skin from losing moisture and becoming excessively dry, and providing a layer of defense against infectious microorganisms.
Seborrhea is the excessive production of sebum. It is important to note that the definition of "excessive" varies with the age and gender of the individual. Sebum production is influenced by age, sex and hormonal status.
Because the largest sebaceous glands are on the face, scalp and groin, these areas are subject to become excessively oily due to seborrhea. All sebaceous glands distribute sebum through a connection to hair follicles, making sebaceous glands and hair follicles the functional units for dispensing sebum to the surface of the skin. The anatomical proximity of sebaceous glands and hair follicles explains why oily skin and oily hair usually occur together in seborrhea. Sebum production is largely controlled by the hormones with the androgenic male hormones playing a central role in both males and females. As males begin to mature into adulthood at about age 13 to 16, androgen levels rise and sebum production increases. Sebum production reaches its highest level in males at about 20, and then slowly declines as male's age. It is interesting to note that Sebum production remains higher in healthy females, but declines markedly after menopause.
The defining symptom and major complaint associated with seborrhea of the scalp is excessive oiliness of the scalp and hair. A greasy-looking scalp is unsightly and excessively oily hair is both unattractive and difficult to style. In males-young males especially-seborrhea often occurs in conjunction with acne (see Acne of the Scalp). Seborrhea can often be managed at home by keeping the scalp clean with shampooing as often as necessary. Some over-the-counter shampoos are labeled for use on oily hair. Seborrhea that is resistant to home treatment should be referred to a physician for examination. Medical treatment may include a medication that reduces sebum synthesis. Additional examination may be necessary if an underlying hormonal dysfunction is suspected.
Seborrheic Dermatitis of the Scalp
Seborrheic Dermatitis is the condition that causes excessive oiliness. Seborrheic Dermatitis shares some features with psoriasis , and some researchers have proposed that seborrheic dermatitis and psoriasis may have some genetic predispositions in common. Other Researchers believe that the cause is a fungal infection. Excessive skin oiliness may be a predisposing factor.
Seborrheic dermatitis is seen most frequently in infants up to 3 months old (when the condition is called "cradle cap"), and in adults over age 30-40, more commonly in men than in women. It is seen frequently in persons infected with the human immunodeficiency virus (HIV), indicating that immune system dysfunction is an underlying or contributing cause of seborrheic dermatitis. An immune dysfunction is also suggested by the frequency of secondary fungal and bacterial infections.
The symptoms and clinical features of seborrheic dermatitis of the scalp include:
Mild to moderate seborrheic dermatitis may be kept in check by frequent shampooing with over-the-counter anti-dandruff shampoos. More severe disease requires medical attention appropriate to the condition; seborrheic dermatitis and psoriasis of the scalp share many features and must be differentiated before treatment.
When a diagnosis of seborrheic dermatitis is confirmed, medical treatment may include:
Diseases and Disorders of the Scalp