what causes seborrheic dermatitis

Seborrheic dermatitis is caused by a combination of factors rather than a single known cause. The main contributors include an inflammatory reaction to an overgrowth of Malassezia yeast, which naturally lives on the skin, especially in oily areas. This yeast overgrowth, combined with immune system overreaction, leads to skin inflammation and the characteristic rash. Other factors that play a role include genetic predisposition, excess skin oil (sebum) production, stress, cold and dry weather, hormonal changes, certain medications, and skin irritants. It is not caused by poor hygiene or allergies. The condition is common in areas of the skin rich in sebaceous (oil) glands, such as the scalp, face, and upper chest. It can be aggravated by stress, fatigue, certain medical conditions (like Parkinson’s disease and HIV), and environmental factors such as weather changes. In infants, hormones from the mother are believed to trigger seborrheic dermatitis, commonly seen as cradle cap. The disease tends to be more frequent in men and people with oily skin. In summary, seborrheic dermatitis results from a complex interplay of yeast overgrowth, immune system response, skin oil, genetics, and environmental triggers.