Acne at 40 years old is usually due to the high production of oil, which is hindered in the process of elimination and blocked in the hair follicles. Acne at 40 is usually caused by the blockage of oil in the passage from the hair follicle to the skin surface. Then the cause of oil blockage may be related to the frequent consumption of spicy, stimulating and greasy food. In addition, excessive use of oily skin care products may also trigger acne, and irregular sleep may cause hormonal disorders in the body, which may stimulate the secretion of oil to block the hair follicles and produce acne. For patients who still have acne at the age of 40, it is recommended that they go to a regular hospital in a timely manner and under the guidance of a professional doctor for active treatment.