Seborrheic dermatitis, also known as seborrheic eczema, is a chronic, papular, scaly, inflammatory skin disease that occurs in areas where sebum is secreted. It can be accompanied by varying degrees of itching and commonly affects areas such as the face and trunk, where sebaceous glands are abundant. It is more frequently seen in adults and newborns. The exact cause of the disease is still not completely understood. It is generally believed to be related to increased sebum secretion, changes in the chemical composition of sebum, and colonization and infection by Malassezia yeasts. Factors like stress, diet, deficiency of B vitamins, and alcohol consumption can also influence the occurrence and development of the disease. Therefore, seborrheic dermatitis is not contagious.