Red pimples on the chest may be caused by acne and Malassezia folliculitis. 1. Acne: Acne occurs on the cheeks and forehead, followed by the chest, back and shoulders, and is mostly symmetrically distributed, often accompanied by enlarged pores and seborrhea. The various types of lesions include pimples at the mouth of hair follicles, inflammatory papules and pustules as well as nodules, cysts and scarring. It can lead to red pimples on the chest. 2. Malassezia folliculitis: Malassezia folliculitis is an inflammatory damage of hair follicles caused by Malassezia. It occurs in the neck, chest, shoulders and back, and is mostly symmetrical. Typical lesions are inflammatory follicular papules, papules or small pustules, hemispherical, 2 to 4 mm in diameter, surrounded by a red halo, which can be extruded powdery fat-like material, often tens to hundreds of dense or scattered distribution. There may be other reasons for the red pimples on the chest, it is recommended to go to the dermatology department for an interview, under the guidance of the physician reasonable medication.