The oil on the scalp with small bumps and hair loss is commonly seen in seborrheic dermatitis, this disease is the result of a combination of intrinsic and extrinsic factors, such as excessive sebum secretion, Malassezia infection, immune response, destruction of the skin barrier, heredity, and so on. 1. Excessive sebum secretion: affected by androgen, seborrheic dermatitis occurs in adolescent men and women with high sebum secretion, more in men than in women, resulting in oily skin, easily blocking pores and causing folliculitis, and in severe cases, affecting the hair follicles leading to alopecia, which is easy to recur. 2. Malassezia infection: Malassezia survives and reproduces in the human body by breaking down sebum and triggers an inflammatory reaction. 3. Immune response: Some studies have found that seborrheic dermatitis patients have decreased T-lymphocyte function, which is related to the body’s immunodeficiency, such as AIDS and other diseases. 4. Skin barrier disruption: The skin barrier function is impaired due to over-cleaning, hair dye stimulation, etc. Therefore, it is more sensitive to local stimuli and more susceptible to microbial and toxin irritation. 5. Genetic factors: There is a genetic correlation for seborrheic dermatitis. If there are symptoms of scalp oil with small bumps and hair loss, it is recommended to see a doctor as soon as possible to receive treatment, so as not to delay the condition.