Blackheads in the underarms are mainly the result of clogged and oxidized sebaceous glands in the underarms. There are abundant follicular sebaceous gland units in the underarms. Underarm hair follicles may be due to sebaceous gland duct keratinization, bacterial reproduction, immune inflammation and other factors, which will make the sebaceous glands enlarge as well as sebum secretion in large quantities. When the hair follicles are proliferated and over-keratinized, blockage occurs, and sebum excretion is blocked, and sebum and keratin plugs are piled up in the mouths of the hair follicles, and the lipids are oxidized into black in contact with the air, thus blackheads are formed. When blackheads appear in the armpit, you should pay attention to the armpit clean, keep the armpit dry, avoid squeezing and scratching the blackheads, you can follow the doctor’s instructions to apply Vitamin A acid, benzoyl peroxide and other medications to treat the blackheads. When blackheads appear in the armpits, you should go to the hospital in time and get timely treatment under the advice and guidance of the doctor.