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AT-A-GLANCE
Seborrheic dermatitis is a common inflammatory skin disease affecting various age groups.
Erythematous, greasy, scaling patches and plaques appear on scalp, face, ears, chest, and intertriginous areas.
Severe forms, like generalized erythroderma, rarely occur.
Etiology is unclear but may be related to abnormal immune mechanism, Malassezia, sebaceous glands, and individual susceptibility.
Treatment is based on symptomatic control.
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Seborrheic dermatitis (SD) is clinically characterized by erythematous, scaly patches on sebaceous gland–rich sites, including scalp, face, upper trunk, and intertriginous areas.1 The affected areas present as various appearances from mild pinkish and sometimes greasy scaling to solid adherent crusts. Patients with this condition complain of discomfort, with symptoms of itching and burning, and also have some serious cosmetic problems, leading to psychosocial distress that has a negative impact on their quality of life.2 SD arises in all races and ethnic groups and has a worldwide distribution, but a higher incidence and more-severe forms are observed in AIDS patients and individuals with certain neurologic conditions, such as Parkinson disease.3
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SD usually appears as a chronic and relapsing pattern in adolescents and young adults when the activity of sebaceous glands increases from hormonal effects, with the incidence increasing in patients with older than 50 years of age.4 SD can also affect babies as young as age 2 weeks with peak incidence at 3 months of age, which is called infantile seborrheic dermatitis (ISD; Fig. 26-1). The overall prevalence of SD in general population is between 2.35% and 11.30%, depending on the study.5 A male predominance is observed in all ages without any racial or regional predilection. SD is often influenced by a seasonal impact. It becomes more common and severe in the cold and dry climates, whereas it may be mitigated by sun exposure. However, several cases induced by treatment of psoralen plus ultraviolet A (PUVA) therapy have been reported.6
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The symptoms of SD are mainly chronic, persistent, and recurrent. The red, flaking, and greasy lesions of scalp and face are easily observed, particularly on nasolabial folds (Fig. 26-2); eyebrows, upper eyelid, forehead, postauricular areas (Fig. 26-3); external auditory canal and auricle (Fig. 26-4), with generally symmetrical distribution. SD can appear in other sites, such as occiput and neck. When the sternal area on the chest (Fig. 26-5), upper back (Fig. 26-6), and umbilicus are involved, petaloid or arcuate ...