There are many causes of red bumps under the nostrils, such as perioral dermatitis, folliculitis, acne and so on. 1. Perioral dermatitis: Perioral dermatitis is most common in young women, and can show red papules on the nose and around the mouth, and in severe cases, pustules may appear, resulting in the phenomenon of red bumps under the nostrils. 2. Folliculitis: Inadequate local hygiene and cleanliness, bacterial infections, and lowered immunity can cause bacterial infections, leading to the phenomenon of red bumps under the nostrils, which are usually accompanied by symptoms such as swelling and pain. 3. Acne: the body’s hormone level secretion is more exuberant, but also lead to the sebaceous glands under the nostrils clogged, thus appearing acne, causing the phenomenon of red bumps under the nostrils. There are many reasons for red bumps under the nostrils, if you can’t get relief for a long time, it is recommended that you go to the hospital in time to improve the examination and give standardized treatment after a clear diagnosis.