Newborns with red rashes may be caused by neonatal toxic erythema, mosquito bites, heat rash and other causes. 1. Neonatal toxic erythema: neonatal toxic erythema is a kind of allergic reaction of the skin caused by the stimulation of foreign materials such as clothing, diapers and shower gel after the birth of newborns, the symptoms are mild and severe, most of which can be reduced by themselves without special treatment, and usually subside within a week. 2. Mosquito bites: newborns’ skin is relatively delicate, mosquito bites, skin will grow a red rash. 3. Heat rash: the newborn’s sweat ducts are not well developed, and the metabolism is relatively fast, the body sweats a lot, usually wrapped in too much clothing or in the high temperature, hot environment, a lot of sweat is not easy to evaporate, epidermal stratum corneum impregnated with swelling, sweat ducts narrowed or blocked, the sweat overflow into the surrounding tissues, it will be long out of the red rash. Newborns with red rashes may also have other causes, such as eczema, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.