Causes of closed acne formation include increased sebum production, elevated androgen levels, and abnormal follicular keratinization. Closed acne is a chronic inflammatory skin disease, mainly manifested as the appearance of pinhead-sized milky white papules on the surface of the skin. 1. Increased sebum secretion: prolonged late nights, obesity, mental stress, high-fat diets, improper cleansing, and the use of poor-quality cosmetics may cause a large increase in sebum secretion, thus triggering closed pimples. 2. Elevated levels of androgen: When the level of androgen rises rapidly, it will prompt the development of sebaceous glands, which will produce a large amount of oil and increase the chances of the occurrence of closed pimples. 3. Abnormal follicular keratinization: abnormal follicular keratinization, such as smaller, clogged and narrowed follicles, will trigger abnormal sebum secretion, thus inducing the formation of closed acne. Closed acne patients should eat a light diet, avoid high sugar, high fat, spicy and stimulating food, eat more fresh vegetables and fruits, drink more water, more exercise can accelerate the metabolism, which can help the treatment and prevention of closed acne, if necessary, timely consultation, and comply with the doctor’s instructions for treatment.