Seborrheic dermatitis and androgenetic alopecia are possible causes of greasy hair and severe hair loss. 1. Seborrheic dermatitis: Seborrheic dermatitis causes two types of damage when it involves the scalp, which ultimately leads to the occurrence of greasy hair and severe hair loss. For scaly scalp damage, the patient’s scalp can appear red spots, small pieces of chaff-like flakes, hair oil secretion, hair thinning, severe hair loss and other symptoms. Scab type scalp damage occurs in more obese patients, in addition to the hair is obviously greasy, hair loss is obvious, patients can also appear on the scalp thicker, flaky, greasy scab. 2. Androgenic alopecia: androgenic alopecia is a common cause of clinical hair loss, and scalp hair follicles are too sensitive to the role of androgens have a certain relationship. In addition to the obvious symptoms of hair loss such as shifting of the hairline on the forehead and temples, baldness, and progressive hair loss, patients may also suffer from increased oil secretion from the scalp, increased dandruff, shrinkage of hair follicles, and thinning and softening of the hair. Therefore, greasy hair and severe hair loss may also be caused by androgenic alopecia. To summarize, it is recommended that patients go to the hospital to clarify the cause of the disease and follow the doctor’s instructions in time to avoid further aggravation of the condition.