Consider oily skin, increased sebaceous gland secretion, and seborrheic dermatitis on the forehead. 1. Oily skin: due to genetic reasons, the sebaceous glands in the skin are more exuberant in secretion, which will lead to greasier skin. 2. Increased sebaceous gland secretion: can be caused by bad habits, if usually often stay up late, or mental stress, often eat some spicy and stimulating food, will also affect the endocrine system leading to increased sebaceous gland secretion of the skin, the symptoms of forehead oil. 3. seborrheic dermatitis: this is a chronic inflammation that occurs in the seborrheic overflow area, and genetic factors, microbial infections and other factors, mainly in the distribution of sebaceous glands, sebum secretion of the parts of the sebaceous gland, due to the inflammation of the infection, there will be greasy symptoms, usually accompanied by mild itching and so on. Oily forehead. There may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.