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Seborrheic Dermatitis: New Formulations for Treatment
Janet G. Hickman, MD
Seborrheic dermatitis is a common cutaneous disorder occurring in at least 3%–5% of the population.1 Dandruff, the less inflammatory form of seborrheic dermatitis, occurs in 50%–80% of teenagers and adults.2
Seborrheic dermatitis is diagnosed clinically by observing:
There may be symptoms of:
There are no diagnostic or necessary laboratory tests and biopsy is seldom needed.
In infancy, seborrheic dermatitis presents as “cradle cap”— thick yellow flaking at the vertex of the scalp. It may also cause diaper dermatitis in infants and intertriginous rash in infants and adults. Seborrheic dermatitis is absent in the preadolescent child but recurs after puberty. The course is usually chronic and intermittent with flares induced by:
Seborrheic Dermatitis in Systemic Disease
Worsening of seborrheic dermatitis is a common finding in Parkinson’s disease and related neurological conditions. Pronounced seborrheic dermatitis is one of the earliest and most common findings in HIV/AIDS, even in the era of highly active antiretroviral therapy (HAART).3
It is important to distinguish seborrheic dermatitis from dermatophyte infections. Scalp flaking with hair loss, or scalp flaking in preadolescent children, especially if accompanied by lymphadenopathy, should be evaluated with microscopic examination and culture to detect tinea capitis. Similarly, finding erythematous flaking areas on the face or body beyond the typical distribution should raise the suspicion of tinea corporis. Lupus erythematosus and rare conditions such as Langerhans cell histiocytosis may mimic seborrheic dermatitis and might be considered if the clinical course and response to treatment are atypical.
While the detailed pathophysiology of seborrheic dermatitis remains to be clarified, the following are involved:
Sebum is necessary to support the growth of Malassezia. Although Malassezia yeasts are common colonizers of most adult scalps, only some individuals develop the flaking and inflammatory response of seborrheic dermatitis. The frequency of positive family histories implies a genetic component to the propensity to develop seborrheic dermatitis. The exact mechanism by which Malassezia yeasts induce inflammation is not fully understood. Lipases created by the organism produce free fatty acids such as oleic acid from sebum. Experimentally, application of oleic acid to scalps of susceptible individuals can mimic the scaling and erythema of seborrheic dermatitis.1 Other proposed mechanisms of inflammation initiation are alternative complement activation and Toll-like Receptor (TLR) stimulation by Malassezia.
Treatment approaches include:
Many patients mistakenly believe the flaking of their face or scalp is “dry skin”; they need to be encouraged to shampoo regularly and use gentle but effective facial cleansers. Greasy and oily face and scalp products can aggravate the condition and should be avoided. It is especially important for African-American patients to find suitable scalp products; newer gel formulations of medications for seborrheic dermatitis may successfully replace greasy pomades.
Vehicle choice is important as the poor barrier function of skin with active seborrheic dermatitis makes it prone to stinging or burning. Propylene glycol containing nonalcohol gels (or anhydrous gels) are well tolerated and have the advantage of being acceptable for hairy areas, e.g., the beard, as they do not leave a residue. Additionally, the use of the anhydrous gel formulation eliminates the potential for adverse effects associated with sodium sulfite-containing cream. Some cream formulas cake on the skin accentuating the flaking, whereas ointments may be too greasy.
Treatment Shampoos for Seborrheic Dermatitis and Dandruff
First-line treatment includes the use of an antiseborrheic (antidandruff) shampoo. The scalp is a reservoir for Malassezia; regular use of a treatment shampoo improves long-term control. Dandruff shampoos depend on the anti-Malassezia efficacy of the following active ingredients:7,8
In general, the efficacy of these active ingredients parallels their anti-Malassezia potency. Note that formulation also makes a difference to efficacy, with micro-dispersed ZPT or selenium sulfide more effective than standard formulas. The incorporation of non-oily conditioners into some antidandruff products makes them more acceptable cosmetically. The addition of menthol can give some short-term itch relief. Salicylic acid, urea, or glycolic acid may assist scale removal. Among herbal products, tea tree oil has shown some efficacy against Malassezia.9,10
Seborrheic dermatitis is a common problem of variable severity which prominently affects the facial skin and scalp surface. Although Dr. Hickman rightly asserts that a biopsy is rarely needed to establish the diagnosis, some degree of medical investigation may be warranted. Ninety to ninety-five percent of those with HIV infection and some 35% of those afflicted with neurological disorders (such as, but not limited to, Parkinson’s Disease) will develop seborrheic dermatitis.1 Hereditary or acquired zinc deficiency may present as seborrheic dermatitis; psoriasis and rosacea may overlap clinically with it; and facial dermatophytosis may closely mimic it.2 Drugs, including gold derivatives, anabolic steroids, cimetidine, psoralens, and some psychotropic agents may induce seborrheic dermatitis.3 Acute onset seborrheic dermatitis may be a sign of eating disorders, such as occult anorexia nervosa or bulimia.4
Because we do not really know the cause of seborrheic dermatitis, we treat a number of putative etiologic factors. This explains why such diverse drugs as anti-inflammatory agents (corticosteroids and topical calcineurin inhibitors), keratolytics (salicylic acid) and anti-fungal agents (ketoconazole and ciclopirox) may be of benefit. Tachyphylaxis is not rare, and therefore periodic rotation of therapeutic agents may be necessary.5 This is particularly evident when treating scalp disease with shampoo products.
As is true of many rosacea patients, those with seborrheic dermatitis are more susceptible to cutaneous irritation.6 This is especially true on the face. Therefore, it is wise to consider the formulation of potential treatment modalities. The newest ketoconazole product is supplied in a rapidly vanishing and well-tolerated anhydrous gel formulation which also has the advantage of once-daily use.
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