Heat rashes are one of the most common rashes in infants and toddlers. They start when something obstructs the openings of sweat glands on the skin, perhaps excessive clothing or because the baby has been lying in one position for a prolonged period. Heat rash is common during summer months because of overheating, but also appears during the cooler fall or winter months, usually because of overdressing. The rash shows up as tiny little red spots and bumps, and is most common on the chest, abdomen, back, neck, and upper arms. Heat rash usually disappears on its own in a day or two. Cool baths may be helpful, and avoidance strategies are important: Avoid "over-swaddling" (dressing your baby in too many layers of clothing) and keep the ambient temperature at a comfortable level. Rashes that look similar to heat rash include viral or fungal skin infections and drug reaction rashes. Your baby's doctor can help to distinguish among these if there is any question.
