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pediatric-skin

Heat Rash in Babies and Toddlers: Small Bumps, Summer Skin

Heat rash causes tiny red or clear bumps from blocked sweat glands. Cooling the skin and avoiding overdressing usually clears it within days.

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Lena Park, PNP — Pediatric NP

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What heat rash looks like

Heat rash presents in a few forms. The most common in newborns is miliaria crystallina, which looks like tiny clear or white water droplets — very superficial and usually not itchy 2. Miliaria rubra, sometimes called prickly heat, causes small red bumps that may feel prickly or itchy; this is the form that most often bothers children 1.

These bumps tend to cluster in areas where sweat collects: the neck folds, under the chin, on the chest, in the diaper area, and in skin creases. In older toddlers who are more active, the back and chest are common sites. The bumps do not usually have pus and are not typically blistered.

Why it happens

Babies and young children have smaller, less mature sweat ducts than adults. When they overheat, their sweat glands activate but the ducts can become blocked by sweat, skin cells, or tight clothing 1. The trapped sweat then leaks into the surrounding skin, triggering inflammation.

Overdressing a baby, using heavy creams or ointments that can block pores, and spending time in hot, humid environments are common contributing factors 2. Babies are not able to regulate their temperature as efficiently as older children and adults, which makes them especially prone to heat rash 1.

Cooling the skin at home

The most effective care for heat rash is removing the source of overheating 2. Moving to a cooler environment — air conditioning or shade — and removing excess layers of clothing allows the skin to breathe and sweat to evaporate.

A gentle, lukewarm bath (not cold) can soothe the skin. Pat skin dry gently rather than rubbing, and keep the affected areas as dry and uncovered as possible. Avoid heavy creams, oils, or ointments on active heat rash, as these can further block sweat ducts 2. Light, breathable, loose-fitting cotton clothing is the best material for a rash-prone baby in warm weather. If air conditioning is unavailable, a fan with a gentle breeze is an alternative 2.

Preventing heat rash

Dressing a baby in a single, breathable cotton layer in warm weather is one of the most effective preventive steps. A general guideline for babies: similar layers to an adult in the same environment, plus at most one light additional layer. Avoiding heavy lotions or petroleum-based products in skin folds reduces pore blockage.

On hot days, limiting time in direct sun and seeking shade or air conditioning for naps and feeding keeps skin cool. Swaddling tightly in warm weather can also contribute to heat rash, so loose, breathable swaddles or sleep sacks are preferable. Avoiding powders (including talcum and cornstarch) is also recommended, as powders do not treat or prevent heat rash and can be inhaled by infants 2.

When home care is not enough

Most heat rash clears within two to three days once the overheating is addressed. If the rash persists beyond three to four days despite consistent cooling measures, if the bumps begin to look filled with pus (miliaria pustulosa), or if the child develops a fever, a provider visit is the right next step 1.

What appears to be heat rash can sometimes be another skin condition — including eczema, a viral rash, or a skin infection — that benefits from an accurate diagnosis. A provider can confirm the cause and advise accordingly.

Common questions

How can I tell heat rash apart from eczema?

Heat rash tends to appear suddenly in warm conditions, clusters in sweaty skin folds, and clears quickly with cooling. Eczema typically shows up in drier, exposed areas like cheeks, elbows, and knees, tends to be itchier, and persists or recurs regardless of temperature. A provider can help sort out the difference if it is not clear.

Should I use calamine lotion or hydrocortisone cream on heat rash?

Cooling the skin is the most effective treatment for heat rash. Calamine lotion may provide mild relief for itchiness. Hydrocortisone cream is not typically recommended without a provider's guidance for heat rash specifically. Most cases resolve simply by reducing heat and avoiding creams that block pores.

My baby has heat rash in the diaper area — is it the same as diaper rash?

Heat rash and diaper rash can overlap in location but are caused by different things. Heat rash in the diaper area often improves when the baby has diaper-free time in a cool environment. If a rash in the diaper area is bright red, raw, or very persistent, a provider can distinguish between heat rash, yeast, and irritant diaper dermatitis.

Talk to a clinician

Lena Park, PNP — Pediatric NP

kids & families. Gale can match you with a licensed clinician for a visit.

Find care →

When to get care right away

  • —Baby develops a fever alongside the rash
  • —Rash bumps become filled with pus or the skin becomes very red, warm, or painful — possible secondary infection
  • —Rash spreads rapidly or does not improve after two to three days of keeping the baby cool
  • —Baby seems excessively sleepy, is not feeding, or is unusually difficult to rouse in a hot environment — possible signs of heat-related illness

If a baby or toddler appears very ill, is limp, very difficult to wake, or is extremely hot to the touch with no sweating, call 911 or go to the nearest emergency department immediately — this may indicate heat exhaustion or heat stroke.

This article provides general health information for parents and is not a diagnosis or personalized medical advice. Consult your child's provider with specific concerns.

References

  1. 1.National Library of Medicine — StatPearls (2024). Miliaria. StatPearls — NCBI Bookshelf. link ✓Miliaria affects up to 40% of infants; immature sweat ducts in infants increase susceptibility; types (crystallina, rubra, pustulosa); warm humid environments and bundling as risk factors
  2. 2.U.S. National Library of Medicine (2025). Babies and heat rashes. MedlinePlus Medical Encyclopedia. link ✓Blocked sweat gland pores as mechanism; avoiding creams and ointments that block pores; light cotton clothing; fans for airflow; avoiding powders; cooler environment as primary treatment

2 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.