Heat rash, which some people call prickly heat or miliaria, is a skin flare that happens after the skin gets too warm. These rashes can feel itchy, uncomfortable, and prickly.
This article gives an overview of heat rash in babies, including pictures to help identify it. We also discuss the causes, treatments, and prevention methods.
Why do babies get heat rash?
Babies are prone to heat rash because they are less able to regulate their body temperature than adults.
Heat rashes appear when sweat gets trapped under the skin. Because babies have smaller sweat glands and are less able to regulate their body temperature, they are more vulnerable to heat rash than adults.
Tight clothes, swaddles, and blankets can also cause heat rashes. In most cases, the rash will go away on its own without treatment.
Babies are more likely to get heat rash for several reasons:
- Babies have little control over their environment and cannot take off extra clothing or move away from heat sources.
- Babies' bodies are less effective at regulating temperature.
- Babies tend to have more skin folds, which can trap heat and sweat.
Types of heat rash
Miliaria occurs when the skin traps sweat. The sweat irritates the outer layer of skin and causes a rash.
Doctors divide heat rash into three types based on its severity:
- Miliaria ruba is the most common type of heat rash. This type of rash happens when there is a blockage in the sweat glands near the surface of the skin, or the epidermis, and the second layer of skin, or the dermis. It causes bumps, discoloration such as redness, and itching.
- Miliaria crystallina is the least severe form of heat rash. It happens when there is a blockage in the sweat glands in the epidermis. This type of heat rash can cause tiny clear or white blisters.
- Miliaria profunda is the most severe type of heat rash, but it is uncommon. When sweat in the dermis leaks into the dermis, it can cause intense flushing and burning. Babies with miliaria profunda may also develop signs of heat exhaustion. The rash may become infected.
With rashes that cause redness, the redness may be easier to see on light skin and more difficult to see on dark skin, though the process causing the redness is the same.
Doctors call the tiny blisters of a heat rash vesicles. Sometimes, these vesicles become inflamed and swollen, causing miliaria pustulosa. This type of heat rash is more prevalent in babies.
Babies with miliaria pustulosa may be less able to sweat, increasing their risk of heat-related illness.
Image credit: Jurfeld, 2018.
Symptoms and diagnosis
For most babies, the only symptom of heat rash is a rash on parts of the body that have had exposure to heat.
Swaddling, warm clothes, poor ventilation, and being near heat sources such as space heaters can all increase the risk. A caregiver might notice a rash on an area of the body that was particularly warm.
Heat rashes are also more likely to appear in skin folds, such as in the neck or groin.
The symptoms of heat rash include:
- a rash that may appear red
- tiny pin-sized blisters on a large area of the skin
- hot skin
Different types of heat rash can have slightly different symptoms:
- Miliaria crystallina can sometimes look similar to tiny beads of sweat trapped under the skin. The blisters do not look red or inflamed.
- Miliaria rubra often itches, so babies may persistently scratch their skin. They may have tiny red bumps or blisters on red and irritated-looking patches of skin.
- Miliaria profunda usually causes deep blisters that may look like pimples. They are usually skin-colored.
- Miliaria pustulosa causes irritated pustules that look like painful blisters. They may scab over or break open and bleed.
In most cases, heat rash clears up fairly quickly and does not cause too much discomfort, so it may not require a trip to the doctor.
The signs of a heat rash are obvious, especially in hot weather. If a caregiver is unsure about a rash, a doctor can usually diagnose the rash based on its appearance.
Treatments and home remedies
Miliaria usually goes away on its own within a few days without treatment.
Caregivers can ease a baby's discomfort and speed up healing with the following methods:
- Move the child to a cool area at the first sign of a heat rash.
- Keep the skin cool and dry.
- Apply a cool compress to the affected area.
- Rinse away oil and sweat with cool water, then gently pat the area dry.
- Regularly clean skin folds to make sure trapped sweat and oil do not make the rash worse.
- Allow the baby to go naked to keep the skin cool.
- Use air conditioning or fans to help keep the skin cool.
- Keep the baby well-hydrated. This may involve nursing breastfed babies on demand and ensuring that older babies have constant access to water.
Do not use rash creams on the skin unless a doctor recommends a specific cream. A heat rash is not an allergic reaction, and it is not dry skin. Using creams that treat these conditions may not help.
For severe heat rashes or rashes that do not go away on their own, a doctor might prescribe a steroid cream to speed up healing.
In rare cases, heat rashes can become infected, especially if a baby scratches them. An infected heat rash may cause a fever and other signs of illness.
If a baby has a fever or seems sick, see a doctor. They might prescribe antibiotics to clear up any bacterial infection.
Dressing a baby appropriately for the climate can help prevent heat rash.
Risk factors for heat rash in babies include:
- wearing clothes that are too warm for the season
- living in a very warm climate
- sitting near heat sources, such as space heaters or heat lamps
- swaddling, especially if the weather is warm or the baby is sweating
To reduce the risk of heat rash in babies, try the following:
- Dress babies in seasonally appropriate clothing. There is no need for babies to always be in a swaddle or covered with a blanket, especially in warm weather.
- Choose loose-fitting, breathable clothing, such as cotton pants or a gown.
- Keep babies out of direct sun.
- In hot weather, use air conditioning and fans to keep babies cool.
- Avoid putting babies directly in front of space heaters or other heat sources.
- Monitor babies for signs of excess sweating. If a baby looks flushed or is sweating, move them to a cooler area.
Heat rash is not usually dangerous. It can, however, be a sign that a baby is at risk of overheating. Overheating can cause a number of serious health issues, so it is important to heed the warning and move the baby to a cooler spot. Keeping the baby cool and comfortable can quickly clear up the rash.
If the rash does not go away on its own within a couple of days, if the baby seems very uncomfortable, or if the rash begins spreading, see a doctor.