Seborrheic Dermatitis

What is seborrheic dermatitis?

Seborrheic dermatitis is a common skin condition in infants, adolescents, and adults. The characteristic symptoms—scaling, erythema, and itching—occur most often on the scalp, face, chest, back, axilla, and groin.
Seborrheic dermatitis is a clinical diagnosis based on the location and appearance of the lesions. The skin changes are thought to result from an inflammatory response to a common skin organism, Malassezia yeast.

Treatment with antifungal agents such as topical ketoconazole is the mainstay of therapy for seborrheic dermatitis of the face and body. Because of possible adverse effects, anti-inflammatory agents such as topical corticosteroids and calcineurin inhibitors should be used only for short durations.
Several over-the-counter shampoos are available for treatment of seborrheic dermatitis of the scalp, and patients should be directed to initiate therapy with one of these agents. Antifungal shampoos (long-term) and topical corticosteroids (short-term) can be used as second-line agents for treatment of scalp seborrheic dermatitis.

Seborrheic dermatitis is a chronic inflammatory dermatologic condition that usually appears on areas of the body with a large density of sebaceous glands, such as the scalp, face, chest, back, axilla, and groin.
Although it can be associated with human immunodeficiency virus infection and neurologic disease (e.g., cerebrovascular event, Parkinson disease), seborrheic dermatitis typically occurs in healthy persons.

Its prevalence is 1% to 3% in the general population and 34% to 83% in immunocompromised persons. It has a bimodal distribution, with peaks at two to 12 months of age and in adolescence and early adulthood. It is more common in men and is typically more severe in cold and dry climates and during periods of increased stress

DIAGNOSIS

Seborrheic dermatitis is a clinical diagnosis based on the location and appearance of lesions.
In infants, it may present as thick white or yellow greasy scales on the scalp; it is usually benign and resolves spontaneously.
adolescents and adults, seborrheic dermatitis typically presents as flaky, greasy, erythematous patches on the scalp , nasolabial folds , ears, eyebrows , anterior chest, or upper back.

The differential diagnosis is lengthy, but the correct diagnosis can usually be made clinically by the characteristic distribution of lesions and varying course of the disease. If the diagnosis is uncertain, a biopsy demonstrating parakeratosis in the epidermis, plugged follicular ostia, and spongiosis can confirm the presence of seborrheic dermatitis. The diagnosis can be challenging in patients with darker skin, but the same principles apply.

PATHOPHYSIOLOGY

Although the pathophysiology of seborrheic dermatitis is not completely understood, the mechanisms of effective therapies coupled with results of recent biomolecular studies provide clues about the causes.

Malassezia yeast seems to cause a nonspecific immune response that begins the cascade of skin changes that occur in seborrheic dermatitis.Malassezia is a normal component of skin flora, but in persons with seborrheic dermatitis, the yeast invade the stratum corneum, releasing lipases that result in free fatty acid formation and cause the inflammatory process to begin.Malassezia thrive in high-lipid environments, so the presence of free fatty acids enhances the growth of the yeast. The inflammation causes stratum corneum hyperproliferation (scaling) and incomplete corneocyte differentiation, which alters the stratum corneum barrier and impairs its function, thus increasing access for Malassezia and allowing water to more readily leave the cells.

Antifungals decrease the Malassezia population, whereas anti-inflammatories such as corticosteroids and calcineurin inhibitors decrease the inflammatory response. Many of the current treatments for seborrheic dermatitis have multiple effects (antifungal, anti-inflammatory, regulation of stratum corneum production), thereby combatting the skin changes on multiple levels. The severity of symptoms can be affected by stress and sun exposure, and often has a variable course despite treatment.

TREATMENT

The treatment of infantile seborrheic dermatitis consists primarily of emollients that help loosen scales (e.g., mineral or olive oil, petroleum jelly). Scales can then be removed by rubbing with a cloth or infant hair brush. One study showed that ketoconazole 1% to 2% cream is effective and seems to be safe when used twice daily for two weeks. There are no shampoos that have been approved by the U.S. Food and Drug Administration for treatment of seborrheic dermatitis in children younger than two years.

Treatment of seborrheic dermatitis in adolescents is identical to that in adults ; the primary goals are to lessen the visible signs of the condition and to reduce pruritus and erythema. Treatment includes over-the-counter shampoos and topical antifungals, calcineurin inhibitors, and corticosteroids . Because seborrheic dermatitis is a chronic condition, ongoing maintenance therapy is often necessary.

SCALP

For mild seborrheic dermatitis of the scalp, over-the-counter dandruff shampoos containing selenium sulfide, zinc pyrithione, or coal tar can control symptoms at a fraction of the cost of other treatments. Tea tree oil shampoo may also decrease symptoms.
For long-term control, antifungal shampoos containing ketoconazole 2% (Nizoral) or ciclopirox 1% (Loprox) can be used daily or at least two or three times per week for several weeks, until remission is achieved.

Once-weekly use of these medicated shampoos can prevent relapse.These shampoos should remain on the hair for at least five minutes to guarantee adequate exposure to the scalp.Depending on the severity of scalp inflammation, topical corticosteroids can be beneficial, but long-term use is associated with adverse effects and can be expensive.

Fluocinolone 0.01% solution (Synalar) or shampoo (Capex) and betamethasone valerate 0.12% foam (Luxiq) can reduce itching and inflammation. For moderate to severe cases, clobetasol 0.05% shampoo (Clobex) twice weekly alternating with ketoconazole 2% shampoo twice weekly can reduce acute symptoms more quickly and maintain control longer after discontinuing use, compared with ketoconazole alone.

What may appear to be a worsening of symptoms despite continued use of a treatment may actually represent the natural, varying course of the disease. Often, reassurance and maintenance of therapy are all that is needed, reserving changes in treatment for persistent worsening of symptoms.
Patients with symptoms that do not respond to any of the therapies outlined above may benefit from systemic anti-inflammatories and should be referred to a dermatologist.