Seborrhea is a common, chronic inflammatory skin condition that primarily affects areas of the body rich in sebaceous glands, which produce oil (sebum). The condition is characterized by increased sebum discharge, often leading to the formation of greasy scales. Seborrheic dermatitis is the official medical term for the resulting inflammatory skin disorder. In adults, a mild form on the scalp is known as dandruff, and in infants, it is called “cradle cap.”
Defining Characteristics and Presentation
The visual characteristics of seborrheic dermatitis involve patches of skin that are red, inflamed, and covered with scales that can be white, yellow, greasy, or flaky. These scales range from fine, loose flakes (common dandruff) to dense, diffuse, and adherent crusts on the scalp. These skin changes are frequently accompanied by sensations of itching (pruritus) and occasionally a burning feeling.
The condition favors areas where oil-producing sebaceous glands are highly concentrated. This includes the scalp, which is the most common site, as well as the face, specifically the sides of the nose, the eyebrows, and the eyelids. Other affected areas include the ears, the chest, the upper back, the armpits, and the groin area.
The presentation differs depending on the age of the individual. In adults and adolescents, the rash tends to be more localized and persistent, often requiring ongoing management. Scaling is usually more prominent at the hairline and around the ears, and the overall course is marked by periods of flare-ups and remission.
In infants, the condition is known as cradle cap and typically appears as thick, greasy, yellowish, or brown scales on the scalp. Cradle cap is usually not itchy or painful for the baby and often resolves spontaneously within the first year of life. However, seborrheic dermatitis in infants can occasionally extend to the face, neck, diaper area, and intertriginous areas (skin folds).
Underlying Causes and Contributing Factors
The development of seborrheic dermatitis is multifactorial, involving the skin’s oil production, a naturally occurring yeast, and the body’s immune response. A microbe called Malassezia yeast, a normal component of the human skin flora, is believed to play a significant role. This lipophilic yeast thrives on the lipids found in the skin’s sebum.
When sebum is overproduced, the Malassezia population proliferates and produces irritating metabolites, such as free fatty acids, causing a local inflammatory response. The skin’s reaction to this yeast overgrowth leads to the characteristic redness, scaling, and inflammation. The effectiveness of antifungal treatments supports this mechanism.
Hormonal factors are implicated, particularly during the two peak periods of incidence: infancy and adolescence. Maternal hormones in newborns stimulate sebaceous glands, leading to the oil production that contributes to cradle cap. Similarly, hormonal changes during puberty increase sebaceous lipid production, creating a favorable environment for Malassezia colonization.
The condition is also influenced by non-microbial and environmental triggers that can cause flares. These factors include high stress or fatigue, changes in season, and certain neurological conditions like Parkinson’s disease. People with compromised immune systems, such as those with HIV infection, show a higher prevalence of the condition.
Management and Treatment Options
Management focuses on modulating oil production, reducing the Malassezia yeast population, and controlling inflammation. For the scalp, over-the-counter medicated shampoos are the first line of defense, containing ingredients like zinc pyrithione or selenium sulfide. These ingredients decrease the colonization of the lipophilic yeast on the skin surface.
Other effective shampoo ingredients include antifungal agents like ketoconazole (available over-the-counter or by prescription), and coal tar or salicylic acid, which help soften and remove thick scales. Shampoos should be applied to the affected area and left on for several minutes before rinsing to allow the active ingredients to work. For mild cases, the frequency of use may be reduced to a maintenance schedule after the condition is brought under control.
For more severe cases or affected areas outside of the scalp, prescription treatments are necessary. Topical antifungal creams, such as ketoconazole or ciclopirox, are applied directly to the skin to reduce yeast colonization. Low-potency topical corticosteroids, like hydrocortisone, may be used for short periods to quickly reduce inflammation and itching during an acute flare.
Alternative prescription options include topical calcineurin inhibitors (pimecrolimus and tacrolimus), which can be used as steroid-sparing agents to manage long-term cases, especially on the face. If self-care measures fail to improve symptoms, or if the skin appears infected, seeking professional medical advice is recommended. In severe or resistant cases, a healthcare provider may consider systemic antifungal medications.