Newborn infants may have Erythema toxicum, a rash that is characterized by patchy redness with central vesicles. The rash is temporary, and the location may move (transient). (Image courtesy of the Centers for Disease Control and Prevention.)

To prevent or treat heat rash in an infant, dress the baby in light-weight cotton, use a fan with a gentle breeze (if air conditioning is unavailable), and avoid the use of powders.

Miliaria are caused by obstruction of the sweat glands. There are three stages of Miliaria called Miliaria sudamina, Miliaria rubra, and Miliaria profunda (listed from mildest and most superficial to the most severe and deep forms). The condition occurs in those exposed to heat for prolonged periods of time, in infants, and in the obese. This picture is a close-up of the most severe form. Note the numerous papules on the surface of the skin.

Erythema toxicum neonatorum is a skin condition seen in about half of newborn infants. It consists of reddish patches that have raised clear bumps in the center. This condition may be present at birth or appear shortly thereafter. It usually lasts several days and clears up without treatment.