Bumps on the chest may be caused by mosquito bites, flat warts, keloids, sebaceous cysts, lipomas and other factors. 1. mosquito bites: mosquito bites may be localized allergic reactions, causing redness, swelling, and also accompanied by a significant itching sensation, resulting in the short-term appearance of pimples on the chest. 2. flat warts: flat warts are caused by human papilloma virus infection, resulting in benign skin growths. If they occur on the chest, localized bumps may appear. 3. Keloids: Keloids can be found on the chest and usually occur in people with keloid scarring. If the local skin is damaged, excessive tissue proliferation, fibrous hyperplasia, keloid can be formed. 4. Sebaceous cysts: The sebum secreted by sebaceous glands cannot be normally discharged from the follicles and accumulates locally, which may form cysts and lead to localized pimples. 5. Lipoma: Lipoma is a slow-growing lump of fat, the cause of which has not been fully clarified, but is considered to be related to heredity, which may lead to localized bumps. In addition, acne, folliculitis, malignant tumors and other diseases can also lead to the appearance of localized bumps. It is recommended not to use medication blindly, but to go to the hospital first for examination to understand the cause, and treat with the doctor’s advice.