A lot of red pimples on the chest may be caused by folliculitis, acne, contact dermatitis and other reasons. 1. Folliculitis: a lot of red pimples on the chest may be folliculitis. Folliculitis is an inflammatory lesion that occurs in the hair follicle and its surrounding tissues, can be single or multiple, usually caused by bacterial infections, may also be caused by fungal infections. It is characterized by red, papular pimples with redness, swelling and pain. It usually resolves spontaneously after pus formation, while severe cases need to be treated with medications such as erythromycin ointment. 2. Acne: Acne occurs in teenagers, the most common parts of the face, chest and shoulders and back may also appear. A lot of red pimples on the chest may be acne, which is related to a variety of factors such as strong secretion of androgens, abnormal keratinization of the periphery of the hair, and Propionibacterium acnes infection. High-sugar and high-fat diets and late nights are triggering factors. 3. Contact dermatitis: If the patient is allergic, the chest area in contact with sensitizing chemical fiber clothing, metal ornaments, allergic symptoms can occur, the local appearance of dense red pimples, accompanied by itching. The red pimples on the chest may also be due to other reasons, it is recommended to consult a doctor in a timely manner to clarify the cause of the targeted treatment. Daily keep local clean, do not squeeze pimples.