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Associate Professor of Dermatology
University of Athens
Dermatology Academic Department
“A Sygros” Hospital
University of Athens
Seborrhoeic dermatitis is a common dermatological disorder with a prevalence of 2–5%. Clinically, it presents with inflammation and desquamation in lipid-rich areas of the skin such as the face, chest and scalp. Dandruff, which affects 5–10% of the population, is considered to be the mildest form of seborrhoeic dermatitis. Considerable amounts of money are spent each year on therapeutic agents in an attempt to eliminate the problem.(1)
Although it is generally accepted that Malassezia yeasts are associated with seborrhoeic dermatitis, most of the evidence comes from the efficacy of anti‑fungal drugs. The mechanism by which the yeast causes the dermatosis is not clear. Studies have shown that Malassezia stimulates cytokine production by human keratinocytes.(2) The lipase enzyme produced by Malassezia has also been suggested to split triglycerides into irritant fatty acids, which induce scaling or release of arachidonic acid.(3) Investigators have also proposed that impaired cell immunity may facilitate fungal survival in the skin.(4) Increased incidence of seborrhoeic dermatitis has been documented in HIV/AIDS patients and patients with neurological disorders such as Parkinson’s disease, multiple sclerosis and depression.(5) Several traditional treatments of seborrhoeic dermatitis are currently being used.
Selenium sulphide,(6) propylene glycol,(7) sulphur and tar-containing compounds(8) have been successfully used, with efficacy attributed to their keratolytic properties. Lithium has also been used,(9) with efficacy attributed to inhibition of the fatty acid production (necessary for Malassezia proliferation) and to anti-inflammatory properties.
In the past, intermediate- and high-potency corticosteroids(10) have been used in the treatment of seborrhoeic dermatitis, due to their anti-inflammatory properties. When adverse long-term effects on the adrenal cortex and on the skin became apparent, interest shifted to low-potency drugs such as hydrocortisone 1%,(11) with excellent results.
This drug type includes zinc pyrithione,(12) which has both keratolytic and antifungal properties, and topical azoles such as bifonazole,(13) miconazole(14) and ketoconazole.(15)
New topical treatments for seborrhoeic dermatitis
The success of ketoconazole in the treatment of seborrhoeic dermatitis has fuelled interest in the efficacy of new antifungal agents.
Fluconazole is an azole derivative commonly used for dermatoses caused by Malassezia spp. A recent open trial reported complete recovery or improvement in all patients with seborrhoeic dermatitis using fluconazole 2% shampoo twice weekly for two weeks. All cultures for Malassezia spp were negative at the end of the treatment.(16)
The efficacy of metronidazole remains controversial. Although one double-blind, randomised study found that metronidazole gel 1% applied twice daily for eight weeks was more effective than placebo in the treatment of seborrhoeic dermatitis,(17) another double-blind trial evaluating metronidazole gel 0.75% applied at the same frequency showed no superiority over placebo.(18)
Ciclopirox olamine has a broad spectrum of antifungal action, in addition to anti-inflammatory properties. A recent trial demonstrated that ciclopirox olamine 1% cream was as effective as ketoconazole 2% foaming gel in the treatment of facial seborrhoeic dermatitis.(19)
Terbinafine is a fungicidal allylamine. A solution of terbinafine 1% has been successfully used in the treatment of seborrhoeic dermatitis.(20)
Topical immunomodulators such as tacrolimus and pimecrolimus are a new class of medications that have been used in the treatment of seborrhoeic dermatitis. They are potent and lack the adverse events associated with the long-term use of topical corticosteroids.
Topical tacrolimus ointment 0.1% was proven to be effective in the treatment of seborrhoeic dermatitis in an open-label study. The effect is attributed to the anti-inflammatory and antifungal properties of the drug, which have been demonstrated in vitro against Malassezia spp.(21)
In a randomised, open-label study, pimecrolimus cream 1% was found to be as effective as betamethasone valerate in controlling the symptoms of seborrhoeic dermatitis, with fewer relapses and no rebounds.(22)
Other topical therapies: natural therapies
In vitro, cinnamic acid reduces the growth of Malassezia spp; therefore, mild formulations may prove to have therapeutic use.(23) A recent report has shown that 90% of honey diluted in warm water could be used in the treatment of seborrhoeic dermatitis.(24) Dandruff has been successfully treated with 5% tea tree oil shampoo.(25) Topical mud treatment has also been suggested to represent an alternative to the treatment of seborrhoeic dermatitis.(26)
Systemic treatments for seborrhoeic dermatitis
Oral treatments may be considered in patients refractory to topical treatment or when seborrhoeic dermatitis is extremely widespread.
Oral ketoconazole 200mg daily for four weeks is an effective treatment of seborrhoeic dermatitis of the scalp and body. However, use of oral ketoconazole for more than four weeks has been associated with an increased possibility of side-effects.(27)
Itraconazole 200mg daily is effective in the treatment of seborrhoeic dermatitis and lacks the marked hepatotoxicity associated with ketoconazole.(28)
Oral terbinafine, although ineffective in the treatment of pityriasis versicolor, may be effective against seborrhoeic dermatitis when administersd at a dose of 250mg/day for four weeks.(29)
UVB (TL-01) phototherapy
Ultraviolet B (UVB) phototherapy has been reported to produce excellent results in the treatment of seborrhoeic dermatitis.30
Seborrhoeic dermatitis is a chronic, recurring, inflammatory skin disorder. Consequently, attention should be given to the long-term control of the disorder. The ideal treatment agent should offer reduced relapses, increased tolerability and long-term safety, thus ensuring high rates of patient compliance. Ketoconazole shampoo for the scalp and ketoconazole or miconazole cream for skin eruption seem to be the preferred drugs in the prophylactic treatment of seborrhoeic dermatitis. The new topical immunomodulators tacrolimus and pimecrolimus might prove a good alternative prophylactic treatment, provided that their long-term safety is confirmed.
Topical antifungal agents remain the mainstay of therapy in seborrhoeic dermatitis. Their advantages include good efficacy and tolerability, as well as low cost. Tacrolimus and pimecrolimus might be considered as second-line treatment, because they offer symptom control as fast as that of corticosteroids and lack the latter’s long-term adverse effects.