Dense small pimples on the forehead may be related to acne, pimples and milia. 1. Acne: The onset of acne is related to factors such as androgen levels, increased sebaceous gland secretion, and bacterial infections, etc. Patients may develop pimples, inflammatory papules, pustules, and cysts on the face and other places. 2. Acne: the onset of acne is mostly related to endocrine, genetic and poor skin care and other factors, the patient’s face, forehead and other places will appear skin color pimples. 3. Corn Papules: The onset of corn papules may be caused by heredity, damaged sweat ducts and other factors, mainly manifested as multiple yellowish-white hard pimples, often occurring on the face. There are many reasons for the dense small pox on the forehead, and it is recommended that patients seek medical examination to clarify the cause of the disease.