Seborrheic dermatitis causes are not very well known, but are probably a combination of the following factors:

Skin oil: Increased production of sebum or skin oil

Yeast: An overgrowth of Malassezia furfur, a yeast that normally lives on the skin, especially the skin with many sebaceous glands

Immune response: Some people develop an immune response to Malassezia for unclear reasons

Other factors that contribute to seborrheic dermatitis include:

-Bacteria

-Genetics

-Hormones

-Nervous system disorders such as Parkinson’s disease

-A weakened immune system

-Underlying illnesses such as HIV, psoriasis, acne, rosacea, epilepsy, eating disorders, and alcoholism

-Triggers such as stress, hormonal changes, use of certain cleaning products or medications, fatigue, seasonal changes, heat or sun

Seborrheic dermatitis is more prevalent in men and especially in cold, dry climates and times. It usually becomes more severe when stress increases. In infants, the condition is often called “cradle cap” and usually resolves on its own. However, in adults, symptoms may improve without treatment or may worsen over several years.