Pimples on the shoulders of infants may be caused by eczema, prickly heat, mosquito bites, allergic reactions, folliculitis and so on. 1. Eczema: Inflammatory skin reactions caused by internal and external stimulation of various factors may result in skin erythema, pimples, accompanied by obvious itching symptoms, repeated scratching and stimulation can cause local skin roughness and thickening. 2. Prickly heat: due to high indoor temperature, or not give the baby in time to reduce clothing, coupled with the baby’s metabolism, may cause prickly heat, manifested as pinpoint red pimples, accompanied by mild itching. 3. Mosquito bites: the skin by mosquito bites may also cause local inflammatory reaction, causing localized skin redness, pimples, and even blisters. 4. Folliculitis: local skin due to scratching and other external causes of secondary bacterial infection, can cause folliculitis, manifested as local skin redness, swelling and pimples or even nodules, positive tenderness, part of the white pus can be seen. The baby shoulder lumps, there may be other reasons, need to go to the hospital in time to check, clear cause, timely treatment.