Heat rash looks like a cluster of tiny bumps, each about 1 to 3 millimeters wide, similar in size to pimples or small blisters. On lighter skin, the bumps typically appear red. On darker skin tones, they often look grey or white. The rash shows up in areas where you sweat the most or where skin rubs together, and it usually clears up on its own within a few days once you cool down.
The Three Types Look Different
Not all heat rash looks the same. The mildest form produces tiny, clear bumps that look like small water droplets sitting on the skin. These are superficial blockages in your sweat ducts, right at the skin’s surface. They don’t usually itch or hurt, and they break open easily.
The most common type, often called prickly heat, goes a level deeper. It produces small red bumps (or grey and white bumps on darker skin) that feel rough to the touch. This version itches, stings, or creates a prickling sensation, which is where the nickname comes from. The skin around the bumps may look inflamed or slightly swollen.
The least common and most severe type affects a deeper layer of skin. It produces larger, firm, flesh-colored bumps. This version is more likely to develop after repeated episodes of heat rash and can be uncomfortable enough to interfere with your body’s ability to cool itself.
Where It Typically Shows Up
In adults, heat rash clusters in skin folds and anywhere clothing creates friction: the crooks of your elbows, behind your knees, under your breasts, along your waistband, in your groin, and around your neck. Anywhere fabric traps heat and moisture against your body is fair game.
In infants, the pattern is slightly different. The rash tends to appear on the neck, shoulders, and chest first. It can also develop in the armpits, elbow creases, and diaper area. Babies are especially prone because their sweat ducts are smaller and more easily blocked.
How It Feels
The mildest form of heat rash produces little to no sensation beyond a slightly rough or bumpy texture. The more common prickly heat version is harder to ignore. It causes mild to moderate itching, a stinging or burning sensation, and a prickling feeling that gets worse with continued heat exposure. The irritation often intensifies when you sweat more or when clothing presses against the affected area. Cooling off, whether by moving to air conditioning or applying a cool cloth, brings noticeable relief.
Heat Rash vs. Eczema and Other Rashes
Several skin conditions can look similar at first glance, but a few details help you tell them apart. Heat rash appears specifically in sweaty, friction-prone areas and improves quickly with cooling. Eczema tends to cause more intense, persistent itching and develops in patterns tied to allergens or irritants rather than heat alone. Eczema patches also tend to be drier and scalier, while heat rash feels rough with tiny distinct bumps.
Folliculitis, an infection of hair follicles, can also mimic heat rash. The key difference is that folliculitis bumps are centered around individual hairs and may develop visible white or yellow heads. Heat rash bumps are more uniform and aren’t hair-centered. Contact dermatitis, caused by an irritant touching the skin, follows the exact shape of whatever touched you (a watch band, a necklace) rather than spreading across sweat-prone zones.
How It Heals
Most heat rash clears up within a few days once you remove the trigger. The bumps gradually flatten, the redness fades, and the prickling sensation stops. You don’t typically need any treatment beyond cooling your skin, wearing loose clothing, and avoiding further sweating in the affected area. Letting the skin air-dry rather than toweling off aggressively helps, too.
If the rash persists beyond a week, or if the bumps start filling with pus, the surrounding skin becomes increasingly swollen and warm, or you develop a fever, those are signs the blocked sweat ducts have become infected. An infected heat rash may also develop crusting or start oozing cloudy fluid, which looks distinctly different from the clear, water-droplet appearance of uncomplicated heat rash.
Appearance on Different Skin Tones
Redness is the hallmark description of heat rash, but that only applies reliably to lighter skin. On medium to dark skin tones, the bumps may appear grey, white, or simply darker than the surrounding skin rather than red. The texture is often a more reliable indicator than color: run your fingers over the area, and heat rash feels like fine sandpaper or a patch of tiny raised dots. If you notice that rough, bumpy texture in a sweat-prone area during or after heat exposure, and it improves with cooling, you’re likely looking at heat rash regardless of whether it appears red.