Prickly heat and heat rash in babies

All ages · health · Reviewed 18 June 2026 · All articles

Few things worry a parent more than spotting an unexpected rash on their baby's skin. The good news is that prickly heat, also known as heat rash or miliaria, is one of the most common and least serious skin conditions babies experience. It tends to appear quickly, looks alarming, and then fades just as fast once you cool your baby down. Understanding what causes it, how to recognise it, and what to do about it will help you stay calm and respond effectively the next time it shows up.

Babies are far more prone to heat rash than older children or adults. Their sweat glands are still immature and their skin is delicate, which means they overheat more easily and their bodies struggle to manage temperature changes efficiently. This article covers everything you need to know, based on guidance from the NHS and the American Academy of Pediatrics (AAP).

What is heat rash and why do babies get it?

Heat rash, known medically as miliaria, occurs when sweat glands become blocked and sweat cannot escape to the skin's surface. Instead, sweat leaks into the deeper layers of the skin, causing irritation and the characteristic bumps or blisters you see. According to the NHS, it most commonly affects babies and young children, particularly in warm or humid weather.

Babies are especially vulnerable for several reasons. First, their sweat glands are not yet fully developed, meaning they are less efficient at regulating body temperature. Second, babies spend a lot of time lying in one position, which means skin surfaces can press together and trap moisture. Third, parents and caregivers often dress babies too warmly out of concern for the cold, not realising that the baby is actually overheating. Car seats, slings, and pushchairs can also trap heat around a baby's body, particularly during warm weather or when going indoors after being outside.

There are different types of miliaria, classified by how deep in the skin the blockage occurs. Miliaria crystallina is the mildest form, presenting as tiny, clear, fluid-filled blisters just under the skin surface. These blisters are very fragile and break easily. Miliaria rubra, which is what most people refer to as prickly heat, involves deeper blockages and causes red, raised bumps that can be itchy or cause a prickling sensation. Miliaria profunda is rarer and involves deeper still blockages, leading to firm, flesh-coloured bumps.

How to recognise heat rash in your baby

Heat rash has several distinctive characteristics that can help you tell it apart from other skin conditions. The rash typically appears suddenly, often within minutes to hours after your baby has been in a hot or humid environment. It tends to show up in clusters or patches rather than scattered spots.

The most common locations for heat rash are the neck, chest, armpits, elbow creases, and groin. These are areas where skin folds trap heat and moisture, or where clothing sits closely against the skin. In young babies, the forehead and cheeks are also common sites because babies cannot easily regulate the heat trapped around their heads. The rash may also appear on the back and shoulders, particularly if your baby has been lying down for a long period.

The appearance varies depending on the type. Miliaria crystallina looks like tiny clear or white dewdrops on the skin surface and tends to be painless. Miliaria rubra (true prickly heat) shows up as small red bumps or spots that may feel rough to the touch. Your baby may seem fussy or uncomfortable, especially in the affected area. Babies cannot tell you that their skin feels prickly, but you may notice them rubbing the area or becoming irritable when clothing touches the affected skin.

Unlike some other rashes, heat rash does not typically cause blistering beyond the superficial crystallina type, and it does not weep or crust over unless it becomes infected. The skin around the bumps usually looks relatively normal, without the widespread dryness or scaling you might see with eczema.

Heat rash versus other baby rashes: telling them apart

One of the most common concerns for parents is working out whether a rash is heat rash or something else. Several other skin conditions can look similar, so it helps to know the key differences.

Eczema (atopic dermatitis) is a chronic condition that causes dry, itchy, inflamed skin. It tends to appear in the creases of the elbows and knees, on the cheeks of young babies, and behind the ears. Eczema skin is persistently dry and rough, and does not clear up simply by cooling the skin down. Heat rash, by contrast, appears suddenly in response to heat and fades within a day or two once the baby is cooled. If your baby has a rash that keeps coming back in the same locations, especially in skin folds, and their skin is generally dry, eczema is more likely. Your GP can confirm this.

Nappy rash (diaper rash) is confined to the nappy area and is caused by prolonged contact with urine and faeces, friction, and sometimes fungal infection. It appears as redness, soreness, or spotty patches in the nappy region. Heat rash can overlap with the nappy area but will also appear in other locations on the body.

Newborn rashes such as erythema toxicum and milia are common in the first weeks of life and are completely harmless. Erythema toxicum looks like red blotches with small yellow or white centres and appears on the face, trunk, and limbs. It comes and goes during the first week or two and does not need any treatment. Milia are tiny white spots caused by blocked pores and are most noticeable on the nose and cheeks. Neither of these is related to heat.

Meningitis rash is a medical emergency. It appears as a red or purple rash of small pinprick spots or larger blotches that do not fade when you press a glass against them (the so-called "tumbler test"). If you suspect meningitis, call emergency services immediately. Heat rash fades under pressure.

What to do when your baby has heat rash

The most important step is to move your baby to a cooler environment and allow the skin to breathe. The NHS and AAP both confirm that heat rash usually clears up on its own within a few days once the underlying cause is removed. Here is how to help your baby feel better.

Cool the environment. If it is hot indoors, use a fan to circulate air or move to a cooler room. Air conditioning can help on particularly hot days, but make sure your baby is not placed directly in front of an air conditioning vent, which can be too cold. The goal is a comfortably cool, not cold, temperature.

Remove excess clothing. Dress your baby in loose, lightweight clothing made from natural fibres such as cotton. These fabrics allow air to circulate and absorb sweat more effectively than synthetic materials. Remove any hats or additional layers that might be trapping heat.

Give a cool bath. A lukewarm or slightly cool (not cold) bath can help lower your baby's skin temperature and provide immediate relief from itching or discomfort. The NHS advises against using any soaps or bath products that might further irritate the skin. After bathing, pat the skin gently dry and allow the affected areas to air dry fully before redressing your baby.

Avoid creams and ointments. It might be tempting to apply moisturiser or baby lotion, but the NHS cautions against using thick creams or ointments on heat rash because these can further block sweat glands and worsen the condition. Calamine lotion is generally considered safe for soothing the itch, and your pharmacist can advise you. Avoid talcum powder, which can be inhaled and cause lung irritation in babies.

Keep the skin dry. After bathing, make sure you pat all skin folds dry carefully, including the neck, behind the ears, underarms, and groin. Moisture sitting in these creases can prolong or worsen the rash.

Check for signs of overheating. Alongside the rash, look out for other signs that your baby may be too hot, including flushed cheeks, sweating, rapid breathing, or feeling hot to the touch on the chest or back. If your baby seems unwell beyond the rash alone, contact your GP or call a health advice line.

When to seek medical help

Heat rash is usually easy to manage at home and clears without medical treatment. However, there are situations where you should seek advice from a healthcare professional.

Contact your GP or call a health advice line if the rash does not improve after two to three days of cooling measures. Also seek help if the rash spreads rapidly, looks different from the typical heat rash appearance, or if your baby develops a high temperature alongside the rash. A temperature of 38 degrees Celsius or above in a baby under three months, or 39 degrees Celsius or above in a baby between three and six months, requires prompt medical attention according to NHS guidelines.

Signs that a heat rash may have become infected include the skin becoming more red and swollen, areas of the rash feeling warm and tender, the appearance of pus or crusting, or your baby becoming increasingly unwell. A skin infection (bacterial secondary infection) will need antibiotic treatment and cannot be managed at home.

If at any point your baby seems very unwell, is difficult to rouse, has a high-pitched or unusual cry, shows a rash that does not fade under a glass, or has a stiff neck, call emergency services immediately. These can be signs of a serious illness.

Preventing heat rash in hot weather

Prevention is largely about managing your baby's temperature and keeping the skin dry. During warm weather or in warm environments, check your baby regularly for signs of overheating. The general guidance from the NHS is to dress your baby in one more layer than you yourself are wearing, though in very hot weather this rule of thumb can lead to overdressing. Use your hand to feel your baby's chest or back (not hands or feet, which are naturally cooler) to gauge their body temperature.

Avoid dressing your baby in tight or synthetic clothing during warm weather. Choose cotton bodysuits, loose vests, and lightweight fabrics. When out in the sun, use shade, a sun canopy on the pram, or lightweight muslin cloths to protect your baby from direct sunlight without trapping heat. Never leave a sun canopy fully closed over a pram in warm weather as this can raise the temperature inside to dangerous levels.

In cars, check the temperature of your baby's car seat before placing them in it, especially if the car has been sitting in the sun. Car interiors heat up very quickly and car seats can become uncomfortably hot. Use a window shade to reduce heat build-up when the car is parked.

If your baby is in a sling or carrier, be aware that the close contact between your body and your baby generates heat. Choose a breathable carrier and check your baby's temperature frequently. Take breaks in cooler areas and offer feeds regularly to keep your baby hydrated.

During hot nights, make sure your baby's sleep environment is not too warm. The NHS recommends a room temperature of between 16 and 20 degrees Celsius for babies. Use lightweight, breathable bedding and check that your baby is not sweating or flushed during the night.

Keep track of your baby's health, feeds, and sleep

Cubby makes it easy to log symptoms, sleep patterns, and feeds when your baby arrives, so you always have clear records to share with your doctor.

Start free

Frequently asked questions

Is heat rash dangerous for babies?

Heat rash is usually harmless and clears up on its own once your baby cools down. However, if the rash looks infected, your baby has a high temperature, or the rash does not improve after a few days, you should contact your doctor or midwife. In most cases, simple cooling measures are all that is needed.

How long does heat rash last in babies?

Most cases of heat rash in babies clear up within two to three days once the baby is moved to a cooler environment and kept comfortable. The superficial crystallina form can disappear within hours. If the rash persists beyond a few days or worsens, consult your GP for an assessment.

Can I put cream on my baby's heat rash?

The NHS advises against using thick creams or ointments on heat rash because they can block sweat glands further. Calamine lotion may help soothe the itch. Avoid talcum powder, which can be inhaled by babies and cause lung irritation. If you are unsure which product to use, ask your pharmacist or GP before applying anything to your baby's skin.

How do I tell the difference between heat rash and eczema?

Heat rash typically appears suddenly after overheating, looks like tiny red or clear bumps on the skin surface, and improves quickly with cooling. Eczema tends to appear in skin folds, is chronically dry and itchy, and does not clear up simply by cooling the skin. If you are unsure about what is causing your baby's rash, see your GP for a proper assessment. They can examine the rash and advise on treatment if needed.

Where does heat rash usually appear on a baby?

Heat rash most commonly appears on the neck, chest, armpits, elbow creases, and groin, as these are areas where skin can rub together or where clothing traps heat. It can also appear on the face, particularly on the forehead and cheeks of young babies. In babies who spend time in carriers or slings, the rash may appear wherever their skin presses against yours.