Prickly heat, also known as miliaria or heat rash, commonly affects infants but can occur in children and adults as well. Heat rash develops when excessive sweating blocks pores in the skin. Because babies and children have smaller pores, they are more prone to heat rash than adults, according to the website, Baby Center.
Symptoms
Babies often develop heat rash in skin folds, such as the insides of the elbows, the armpits, neck and chest, and groin. Children and adults usually develop heat rash in skin folds and where clothing rubs on the skin. The rash can appear as tiny red bumps or clear blisters. In some cases the rash can feel annoyingly prickly or itchy.
Types
MayoClinic.com lists three types of heat rash classified by the depth of the skin affected.
Miliaria crystallina, the mildest form of heat rash, affects only the surface of the skin. Common in infants, this type of heat rash causes tiny, clear blisters that are not itchy or painful.
In miliaria rubra, the blockage extends deeper into the outermost layer of skin. Babies between 1- to 3-weeks-old often develop this type of heat rash, characterized by itchy red bumps and a lack of sweat on the affected areas.
The final and most serious type of heat rash, miliaria profunda, extends into the dermis under the outermost layer of skin. Usually this type only affects adults with a history of chronic miliaria rubra, causing goosebump-like nodules and lack of sweating that can cause heat exhaustion.
Cause
While not serious in itself, heat rash is a sign of overheating. MayoClinic.com explains that it occurs when excessive sweating blocks the sweat ducts, so that more sweat becomes trapped under the surface of the skin. Children can develop heat rash after playing hard outdoors in hot, humid weather. Heavy lotions and creams that block the sweat ducts, for example thick sunscreen, can contribute to heat rash. Children can also overheat while playing outdoors in the winter if they are over-dressed against the cold. A medication for attention-deficit/hyperactivity disorder called clonidine can also cause heat rash in kids, says MayoClinic.com.
Treatment
Heat rash will clear up on its own and most cases do not require any medications or special treatments. Allowing the child to cool down treats heat rash effectively. Baby Center recommends applying a cool, wet washcloth or a lukewarm bath with some baking soda to speed the process. Once the skin has cooled, the rash rapidly disappears.
Prevention
Dressing children in light-weight, "breathable" clothing and having them avoid hard play in hot humid weather can help prevent heat rash. Loose-fitting, natural fibers such as cotton are best for keeping cool. MayoClinic.com also recommends avoiding heavy creams or lotions on the skin because they can block pores.
