Causes and Risk Factors of Seborrheic Dermatitis

Seborrheic dermatitis is a common skin rash that manifests as red patches with overlying greasy, yellow scales. There is no single cause for the condition, but a variety of risk factors have been noted and there is suspicion about the role of a yeast. The rash is found on parts of the skin that produce lots of oil, such as the scalp, face, upper chest and back, armpits, and groin.

Most experts theorize that there are likely multiple factors working together that ultimately make a person vulnerable to manifesting this inflammatory skin condition. 

One factor frequently linked to the pathogenesis behind seborrheic dermatitis involves a yeast species called Malassezia. This fungal organism normally lives on the skin, but experts suspect that for some reason, those with seborrheic dermatitis mount an abnormal inflammatory or irritative response to its presence.

More specifically, experts propose that Malassezia yeast invades the outer layer of the skin (called the stratum corneum) and releases enzymes (called lipases) that result in free fatty acid formation. These fatty acids then induce the inflammatory process by reacting with triglycerides produces by the sebaceous (oil-producing) glands in the skin.

Despite the scientific evidence pointing towards a connection between seborrheic dermatitis and Malassezia, experts still debate about the strength of the link, and whether it's a direct or indirect one.

Besides the presence of or a person's reaction to the Malassezia organism on their skin, research has found that age and gender may affect who is more susceptible to developing seborrheic dermatitis.

Seborrheic dermatitis is slightly more common in men, which suggests a possible association with sex hormones, like androgens. Seborrheic dermatitis is also more common in people within these two age groups:

• Infants that are three months of age or younger
• Adults between the ages of 30 and 60 years old

While seborrheic dermatitis generally affects healthy individuals, people with certain underlying medical conditions are more prone to manifesting the rash.

Examples of these medical conditions include:

• Parkinson's disease
• Other neurological conditions (e.g., epilepsy and traumatic brain or spinal cord injury)
• Human immunodeficiency virus (HIV)
• Recovering from a stroke or heart attack
• Chronic alcoholic pancreatitis
• Hepatitis C virus
• Down syndrome
• Certain psychiatric diseases like depression or eating disorder
• Zinc deficiency

Similar to having a certain medical condition, people who take these medications are also more susceptible to developing seborrheic dermatitis:

• Interferon
• Lithium
• Psoralen and ultraviolet A (PUVA) therapy

Interestingly, the connection between genetics and the development of seborrheic dermatitis is receiving more and more attention.

In fact, scientists have found 11 gene mutations or protein deficiencies linked to seborrheic dermatitis. The majority of these genes or proteins play a role in the functioning of the immune system or how cells in the outer layer of the skin mature (called epidermal differentiation).

By understanding how genes play a role in the development of seborrheic dermatitis, researchers can better target therapies to ultimately treat this benign, yet potentially burdensome, skin disease.

Besides your genes, age, gender, and health-related factors, various lifestyle-related factors have been linked to seborrheic dermatitis. These factors include:

• Living in a cold, dry climate
• Emotional stress
• Sleep deprivation

Seborrheic dermatitis, while harmless, can be a frustrating, if not a distressing disease for some people. In adults, particularly, seborrheic dermatitis tends to be chronic and relapsing. This means that having a good treatment plan in place is key to keeping the disease at bay.

If you think you have seborrheic dermatitis, be sure to make an appointment with your primary care physician or dermatologist.