Seborrheic dermatitis (SD) is a chronic and relapsing inflammatory skin condition of sebum-rich areas such as the scalp. It is characterized by erythema, mild- to- moderate scaling resulting in an oil and flaky scalp and is sometimes associated with pruritus. In the adult population, its prevalence is up to 5%, with a higher prevalence in immunocompromised patients and in patients with neurological condition. When only mild scaling without visible inflammation is observed, SD is called dandruff. The prevalence of dandruff in the general population has been estimated between 15% and 20%. Various environmental, intrinsic and host immune factors may contribute to the development of SD, leading to an alteration of the sebaceous gland activity and sebum composition, epidermal barrier function and skin surface fungal colonization, which ultimately leads to inflammation. Among these factors, lipophilic Malassezia fungi may play a key role.¹