Seborrheic dermatitis (SD) is a common inflammatory skin condition that mainly affects young adults and includes areas with a high concentration of sebaceous glands, like the scalp, face and trunk. 

SD can present as mild patches to diffuse scaling on the scalp. In infants, it appears as yellowish, scaly patches known as "cradle cap". Several environmental triggers, such as fungal colonization by Malassezia spp., sebaceous gland activity, immunosuppression and endocrine, neurogenic and iatrogenic factors, may promote SD development in adults. However, in children, excessive sebaceous gland activity from maternal hormones and cutaneous microbiome alterations may trigger early-onset SD.

SD is typically diagnosed clinically, and laboratory or instrumental investigations are rarely required. Treatment targets modulating sebum production, reducing skin colonization by Malassezia spp. and controlling inflammation. 

In adults, mild-to-moderate scalp SD is treated with topical antifungals (like 2% ketoconazole, ciclopirox, miconazole) or anti-inflammatory (utilizing mild-to-moderate potency corticosteroids) or keratolytic/humectant (propylene glycol) agents. Mild-to-moderate facial or body areas SD are treated with topical ketoconazole 2%, ciclopirox, clotrimazole, mild-to-moderate potency corticosteroids, lithium succinate/gluconate and topical calcineurin inhibitors. However, in severe and/or resistant cases, systemic antifungal therapies, like terbinafine and itraconazole, and UVB phototherapy may be administered. 

In children, baby shampoos with emollient agents and vegetable oils or medical device shampoos with anti-inflammatory and antifungal properties containing piroctone olamine, bisabolol, alyglicera and telmesteine, are recommended. Besides pharmacological treatments, a suitable cosmetic approach may also improve therapeutic outcomes if correctly prescribed.

Clinical guidance on 2% ketoconazole use:

• Ketoconazole, 1% to 2% shampoo, can be applied twice weekly for 4 weeks. Ketoconazole, 2% shampoo, applied once weekly for 6 months, can prevent relapse. 
• Ketoconazole, 2% foam, can be used twice daily for 4 weeks. This regimen, followed for up to 12 months, has shown high safety profile.
• Ketoconazole, 2% gel, can be applied twice weekly for 4 weeks. This regimen has demonstrated fast efficacy and a low rate of recurrences after discontinuation.
• Ketoconazole 2% foaming gel is given twice weekly for 1 month, followed by once weekly for 3 months. This regimen has shown a substantial reduction of erythema and Pityrosporum orbiculare count.

Source: DallOglio F, Nasca MR, Gerbino C, Micali G. An overview of the diagnosis and management of seborrheic dermatitis. Clin Cosmet Investig Dermatol. 2022;15:1537-48.