Heat rash — medically known as miliaria — is one of the most common skin complaints in babies and young children during the warmer months. It occurs when sweat glands become blocked, trapping perspiration beneath the skin. While rarely serious, it causes significant parental anxiety, and pharmacists are often the first port of call. Effective advice on cooling, clothing and when to seek further help can resolve most cases within days.
Why Babies Are Particularly Vulnerable
Infants are more susceptible to heat rash than adults for several reasons:
- Their sweat glands are not fully mature and block more easily
- They have a higher surface-area-to-body-weight ratio, making them more sensitive to ambient temperature
- They cannot remove their own clothing or communicate discomfort effectively
- Well-meaning parents often overdress babies, particularly in the first months of life
Heat rash in babies most commonly appears in skin folds (neck, armpits, groin, elbow creases), on the chest and back, and in areas where clothing sits tightly against the skin.
Types of Heat Rash
| Type | Appearance | Severity |
|---|---|---|
| Miliaria crystallina | Tiny clear fluid-filled blisters, no redness | Mildest — superficial duct blockage |
| Miliaria rubra ("prickly heat") | Red bumps, itchy/prickly sensation, may be surrounded by redness | Most common — mid-level duct blockage |
| Miliaria profunda | Flesh-coloured deeper papules, less itchy | Rare in UK — deep duct blockage, usually after repeated episodes |
In babies, miliaria crystallina and miliaria rubra are the forms pharmacists will encounter. Miliaria crystallina often resolves spontaneously within hours once the baby cools down. Miliaria rubra may take 2–3 days to clear with appropriate management.
Pharmacy Treatment
Cooling measures (first-line)
The most effective treatment is cooling the skin to allow the sweat glands to unblock:
- Move the child to a cooler environment — air-conditioned room, shaded area, or a room with a fan (not blowing directly onto the baby)
- Remove excess clothing — dress in a single layer of loose, breathable cotton
- Tepid bath or sponge — not cold, which can cause shivering and paradoxical heat generation
- Allow air circulation — avoid wrapping in blankets, sleeping bags or tight swaddles during warm weather
OTC products
- Calamine lotion — can be applied to affected areas to soothe itching and provide a cooling sensation. Safe for use on babies and children of all ages
- Emollient cream (Diprobase, Cetraben, Doublebase) — use sparingly if the skin is dry. Heavy emollients can potentially worsen blockage in acute heat rash, so advise thin application and avoid greasy ointment formulations
- Hydrocortisone 1% cream — for miliaria rubra with significant inflammation. Suitable for children over 10 years on the body (over-the-counter supply). For younger children, pharmacists can advise parents to see their GP if hydrocortisone is needed
- Antihistamines — chlorphenamine (from age 1) may help with sleep disruption caused by itching. Cetirizine (from age 2) or loratadine (from age 2) for daytime itch relief
What NOT to recommend
- Talcum powder — historically used but now discouraged due to inhalation risk in infants and potential to further block pores
- Thick barrier creams (e.g. zinc oxide nappy cream) — on heat rash areas, these trap heat and worsen the condition
- Fragranced products — can irritate already inflamed skin
Distinguishing Heat Rash From More Serious Rashes
Parental concern about rashes in babies is understandable, and pharmacists should be alert to features that suggest something other than heat rash:
| Feature | Heat rash | Consider referral |
|---|---|---|
| Fever | No fever | Fever with rash — may indicate infection |
| Distribution | Skin folds, clothed areas | Widespread, including palms and soles |
| Glass test | Blanches under pressure | Non-blanching rash — urgent referral (possible meningococcal disease) |
| Child's behaviour | Irritable but feeding well | Lethargic, refusing feeds, inconsolable |
| Duration | Resolves in 2–3 days with cooling | Persisting beyond 5–7 days despite cooling measures |
| Appearance | Small bumps/blisters, no pus | Pustules, crusting, spreading redness — possible bacterial infection |
Red flag: Any non-blanching rash in a baby or child requires immediate medical assessment. The glass test (pressing a clear glass against the rash to see if it fades) should be explained to parents at every opportunity.
Prevention Advice for Parents
Pharmacists can offer the following preventive guidance:
- Dress babies in one layer more than you would wear yourself — the traditional advice, but many parents interpret this too generously in summer. In a warm house (above 22°C), a vest alone or even a nappy alone is often sufficient
- Use cotton or bamboo fabrics — these are more breathable than synthetic materials
- Avoid direct sun exposure for babies under 6 months (sunscreen is not recommended under 6 months either)
- Keep the bedroom cool — room temperature of 16–20°C is ideal for infant sleep
- Check the baby's temperature by feeling the chest or back of the neck — hands and feet are unreliable indicators as they are normally cooler
- Use a fan in the room if air conditioning is unavailable — point it at the wall to circulate air without direct airflow onto the baby
When to Refer to the GP
Advise parents to see their GP if:
- The rash does not improve within 3–5 days despite cooling measures
- The baby develops a fever alongside the rash
- There are signs of secondary bacterial infection (pustules, weeping, spreading redness)
- The rash is non-blanching (urgent same-day referral or A&E)
- The child is under 3 months with any rash (lower threshold for assessment)
For more information on pharmacy services for children and families, visit PharmSee's pharmacy finder or explore pharmacy services in your area.
Sources: NHS England, NICE CKS Rashes in Children, British Association of Dermatologists, Lissauer and Clayden's Illustrated Textbook of Paediatrics.