Skin Care Heat Rash: What Is It and What Causes It? By UPMC, June 12, 2018 The term heat rash is frequently used as a catch-all for a variety of heat-related skin conditions. But what is the true definition of heat rash and what are some typical heat rash symptoms? Knowing how to spot heat rash can help you and your doctor pinpoint the best heat rash treatment. Get expert dermatology care in Pennsylvania, when you need it. Learn more about UPMC eDermatology. What Causes Heat Rash? Heat rash, also called “prickly heat” or “miliaria” is a skin condition that can affect babies, children, and adults in hot weather. The rash usually occurs when your sweat ducts become blocked and perspiration is trapped under your skin. Heat rash often occurs in the summer or in humid climates. Babies are top candidates for heat rash when their parents dress them in clothing that is too hot for the temperature. However, adults can also experience heat rash when they are dressed too warmly or when they stay outside too long in hot and humid weather. RELATED: What’s the Difference Between Sunburn and Sun Poisoning? Know the Heat Rash Symptoms Heat rash symptoms are not difficult to detect. A common sign of heat rash is a cluster of red bumps that resemble pimples on the skin. The red bumps, which can look like blisters, typically pop up on the neck, chest, and arms. They tend to accumulate in places with creases, such as elbow creases, armpits or under the breasts. Some types of heat rash can make you feel an itchy or prickly sensation on your skin. There are different forms of heat rash that can range in severity, so if you think you might have heat rash, consult your doctor. Heat Rash Treatment The best heat rash treatment depends on the severity of the condition. In many cases, removing yourself from the warm environment to a cooler, less humid atmosphere can resolve the issue, according to the Centers for Disease Control. Consider using a dusting powder to promote comfort, and an anti-itch cream can also help relieve itching and discomfort. If your rash symptoms worsen or last longer than a few days, it may be time to visit your doctor. Prolonged symptoms could mean the heat rash has become infected. Look for signs of infection, such as pus, increased pain, swelling, warmth around the affected area, swelling, swollen lymph nodes, a fever, or chills. RELATED: Hydration 101: What You Need to Know Heat rash is a treatable condition when you know what to look for and how to take care of it. For more information on heat-related illnesses and how they affect skin care, contact the UPMC Department of Dermatology.