Hello, pimples all over back,, or over chest is called as tropical acne, and A boil is a red, swollen, painful bump under the skin. It often looks like an overgrown pimple.Boils are often caused by infected hair follicles. Bacteria from the infection form an abscess, or pocket of pus., this needs to be treated with antibiotic, and other additives, please consult a dermatologist.