Heat rash: How to spot it and what to do

July 2026 tied with July 2024 as the warmest July ever recorded worldwide, while the contiguous United States experienced its hottest month on record. As lingering heat waves continue to affect communities across the country, the U.S. Centers for Disease Control and Prevention is warning people to recognize and prevent heat-related illnesses, including heat stroke, heat exhaustion, and heat cramps.

But one heat-related condition that people do not always recognize is heat rash. Because its symptoms can resemble other skin problems, many people may not immediately recognize it as a heat-related illness.

What is heat rash?

Heat rash is also known as miliaria or prickly heat. It is caused when ducts from eccrine sweat glands that lead to the skin's surface are blocked or inflamed.

Eccrine sweat glands help your body maintain a steady temperature. When your internal temperature rises, these glands release water that rises to the surface of your skin through tiny ducts. There it quickly evaporates, cooling your skin and the blood beneath.

However, sweat ducts may get blocked when you sweat excessively in hot temperatures, particularly if skin folds or tight-fitting clothes hinder their function. Sweat is then trapped beneath the skin, causing inflammation in the form of a rash.

What are the signs of heat rash?

Heat rash appears as small, itchy, red bumps that may resemble tiny pimples or blisters. In people with darker skin tones, these small, itchy bumps may not appear red, but will look slightly darker than surrounding skin.

Where and when is heat rash likely to occur?

Heat rash can appear on the neck, scalp, chest, groin, or elbow creases.

Heat rash can occur whenever the body sweats, making it common in hot, humid climates and during exercise, fever, or hospitalization.

Heat rash also can occur in newborns, as their eccrine sweat glands are not fully developed. In newborns, heat rash looks like very thin blisters or water drops widely distributed on the face, trunk, arms, and legs. Call your pediatrician for advice if you notice a rash like this.

How can you treat heat rash?

Heat rash is usually easy to treat with home remedies. These same measures can help relieve symptoms and prevent heat rash in both adults and babies.

• Cool down. The first step is to get out of the heat and cool and dry your skin. Use a fan or air conditioner, take a cool shower, or apply cool compresses to the affected areas. It's important to know that some people are more vulnerable to heat, and to make plans to help stay safe when temperatures are dangerously high.
• Prevent irritation. To prevent skin irritation, avoid wearing clothes made from synthetic materials, which can trap heat. (While dry-fit clothing helps to wick away moisture from the skin, it often can be too tight fitting.) Instead, wear light, loose-fitting cotton clothing that allows airflow over your skin. If a heat rash occurs around your groin area, avoid wearing undergarments until it clears up.
• Try anti-itch products. Use an over-the-counter topical corticosteroid cream or calamine lotion for itching. However, avoid baby powder, oily or greasy moisturizers, and sunscreen, as they can further block sweat ducts.

Heat rash typically goes away within one to two days once you cool down your body. More severe heat rashes can last a week or longer. See your doctor (or follow up with your pediatrician) if a heat rash has not cleared up after a week. Also seek immediate care if you experience pain, intense itching, or the rash appears infected.