Heat rash â€” also known as prickly heat and miliaria â€” isn't just for babies. Though it's most common in infants, heat rash affects up to a third of adults living in tropical climates and can plague anyone during hot, humid weather.
Heat rash develops when your sweat ducts become blocked and perspiration is trapped under your skin. Symptoms range from superficial blisters to deep, red lumps. Some forms of heat rash can be intensely itchy or prickly.
Most often, heat rash goes away on its own. Severe forms of heat rash may need medical care, but the best way to relieve symptoms is to cool your skin and prevent sweating