Causes

Seborrheic dermatitis is thought to be due to a combination of an over production of skin oil and irritation from a yeast called malessizia.

Seborrheic dermatitis appears to run in families. Stress, fatigue, weather extremes, oily skin, infrequent shampoos or skin cleaning, use of lotions that contain alcohol, skin disorders (such as acne), or obesity may increase the risk.

Neurologic conditions, including  Parkinson's disease, head injury and stroke may be associated with seborrheic dermatitis. Human immunodeficiency virus (HIV) has also been linked to increased cases of seborrheic dermatitis.

Symptoms

Seborrheic dermatitis can occur on many different body areas. Usuallky it forms where the skin is oily or greasy. Commonly affected areas include the scalp, eyebrows, eyelids, creases of the nose, lips, behind the ears, in the outer ear, and middle of the chest.

Seborrheic dermatitis in infants, also called cradle cap, is a harmless, temporary condition. It appears as thick, crusty, yellow or brown scales over the child's scalp. Similar scales may also be found on the eyelids, ear, around the nose, and in the groin. Cradle cap may be seen in newborns and small children up to age 3 .

Cradle cap is not contagious, nor is it caused by poor hygiene. It is not an allergy, and it is not dangerous. Cradle cap may or may not itch. If it itches, excessive scratching of the area may cause additional inflammation, and breaks in skin may cause mild infections or bleeding.

In general, symptoms of seborrheic dermatitis include:

Skin lesions
Plagues over large area
Greasy, oily areas of the skin
Skin scales - white and flaking, or yellowish, oily and adherent -- dandruff
Itching - may become more itchy if it gets infected
Mild redness
Hair loss

Signs & Tests

The diagnosis is based on the appearance and location of the skin lesions.

Treatment

You can treat flaking and dryness with over-the-counter dandruff or medicated shampoos. Shampoo the hair vigorously and frequently (preferably daily). Loosen scales with the fingers, scrub for at least 5 minutes, and rinse thoroughly. Active ingredients in these shampoos include salicylic acid, coal tar, zinc, resorcin, ketoconazole, or selenium.

Shampoos or lotions containing selenium,ketoconazole, or corticosteroids may be prescribed for severe cases. To apply shampoos, part the hair into small sections, apply to a small area at a time, and massage into the skin. If on face or chest, apply medicated lotion twice per day. Recently, creams classified as topical immune modulators are being used.

Seborrheic dermatitis may improve in the summer, especially after outdoor activities.

For infants with cradle cap:

1. Massage your baby's scalp gently with your fingers or a soft brush to loosen the scales and improve scalp circulation.

2. Give your child daily, gentle shampoos with a mild soap while scales are present. After scales have disappeared, you may reduce shampoos to twice weekly.

3. Be sure to rinse off all soap.

4. Brush your child's hair with a clean, soft brush after each shampoo and several times during the day.

5. If scales do not easily loosen and wash off, apply some mineral oil to the baby's scalp and wrap warm, wet cloths around his head for up to an hour before shampooing. Then, shampoo as directed above. Remember that your baby loses a lot of heat through his scalp. If you use warm, wet cloths with the mineral oil, check frequently to be sure that the cloths have not become cold. Cold, wet cloths could drastically reduce your baby's temperature.

6. If the scales continue to be a problem or concern, or if you child seems uncomfortable or scratches his scalp, contact your physician. He may prescribe a cream or lotion to apply to your baby's scalp several times a day.

Seborrheic dermatitis is a chronic (life-long) condition that can be controlled with treatment. It often has extended inactive periods followed by flare-ups. A more extreme form of this condition overlaps with psoriasis of the scalp and is called sebopsoriasis.

Complications

• Psychological distress, low self esteem, embarrassment

• Secondary bacterial or fungal infections

Call for an appointment with your health care provider if seborrheic dermatitis symptoms do not respond to self-care or over-the-counter treatments.

Also call if patches of seborrheic dermatitis drain fluid or pus, form crusts, or become very red or painful.

Prevention

The severity of seborrheic dermatitis can be lessened by controlling the risk factors and by paying careful attention to skin care.

References

Hbif TP, ed. Clinical Dermatology, 5th ed. Philadelphia, PA:  Mosby Elsevier; 2009.