Patients Should Avoid Greasy Lotions, Laura E. Skellchock, M.D.

Seborrheic dermatitis is a chronic, recurrent, benign inflammatory condition affecting areas of the skin that are rich in sebaceous glands.  It is relatively common, with an estimated incidence of 2 to 5 percent of the population. It is seen more often in males, and peaks in infants up to 3 months old and then again in adults between the ages of 30 and 60. More involved cases are seen in patients with AIDS or Parkinson’s disease.

Etiology

The exact cause of seborrheic dermatitis is unknown, but both sebum and microbes contribute to its development. Patients with seborrheic dermatitis often have enlarged sebaceous glands. The proportion of lipid components seems to change in this condition. Compared to normal skin, the proportion of cholesterol, triglycerides, and paraffin is increased while the proportion of squalene, free fatty acids, and wax esters is decreased.  Follicular organisms such as Pityrosporum ovale may be causative factors since a decrease in their population is associated with a clearing of the condition. Seborrheic dermatitis is seen in a variety of neurologic conditions, thus implicating the nervous system. In Parkinson’s disease, sebum production is increased, and seborrheic dermatitis often improves after treatment with levodopa.  Patients with supraorbital injuries, polio, facial paralysis, quadriplegia, or syringomyelia have seborrheic dermatitis more often than expected. Extensive, severe cases of seborrheic dermatitis often are associated with AIDS. Emotional stress often exacerbates the condition, as can the dry, cool air of the winter season.

Clinical Manifestations

All patients with seborrheic dermatitis tend to have oily skin, especially of the face, upper back, shoulders, chest, axillae, and groin. The skin in these areas is erythematous and scaly, with prominent follicular openings.  Infants up to 3 months old are affected primarily on the scalp (cradle cap) and intertriginous areas.

Involvement of the scalp can be dramatic, with extension onto the frontal forehead, auricular grooves, and ears. This condition may be complicated by otitis externa. The dermatitis may predispose these areas to infections with bacteria and candida. In any child whose condition is especially tenacious or chronic, one must consider conditions such as scabies, atopic dermatitis, or Histiocytosis X.  Leiner’s disease is characterized by widespread exfoliative erythroderma. Infants with this disorder are quite ill, with vomiting, diarrhea, anemia, and skin infection. Deficiency in leukocyte chemotaxis or low levels of C5 inhibitor may be at fault.

Adults with seborrheic dermatitis have yellowish erythematous scaling plaques in the scalp, temples, eyebrows, glabella, supra- and retroauricular grooves, external ear canals, paranasal skin and nasolabial folds. Widespread dandruff is the simple way to describe this. More extensive disease can involve the mid-upper chest and back, axillae, suprapubic abdomen, and crural folds. Blepharitis involving the lid margins and eyelashes can be seen as well. Itching, stinging, blurred vision, and even conjunctivitis may occur. The most severe skin cases can become generalized, leading to erythroderma. Complications of high cardiac output and infection must be ruled out in these cases.  Depending on the site of involvement, the differential diagnosis in adults includes psoriasis, atopic dermatitis, external otitis media, contact dermatitis, pityriasis versicolor, pityriasis rosea, candidiasis and rosacea.

Treatment

In infants, treatment should be aimed at removing the excess crust and doing no harm. Frequent washing of the scalp and the use of mineral or vegetable oil to loosen the crusts can be all that is necessary. In more difficult cases, low-potency topical steroids such as hydrocortisone can be used briefly. Any secondary skin infection must be adequately treated.  In adults, the disease course is often more chronic and intermittent; patients should be informed of this. Regular use of a dandruff shampoo is often adequate treatment. Shampoos containing selenium sulfide, zinc pyrithione, chloroxine, sulfur and salicylic acid, or tar preparations are helpful. The proven efficacy of the recently developed ketoconazole shampoo reinforces the role of P.  ovale in the etiology of this disorder.  The shampoo must stay in contact with the scalp for 10 to 15 minutes for maximal results. To remove stubborn scale, keratolytics containing salicylic acid or simple oils are applied to the scalp at bedtime and covered with a shower cap.  For more difficult cases, application of a topical liquid corticosteroid may be required. Topical antifungal creams often are efficacious as well.

Explain to patients that various factors are involved in the development of this skin disease. Caution them to avoid any conditions that they feel exacerbate their condition, including extremes of weather, greasy lotions and creams, and excessive stress.

Dr. Skellchock is Clinical Associate Professor of Dermatology at the University of California, San Francisco, and a dermatologist at Kaiser Permanente in Oakland, California.

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