Miliaria Crystallina (Sudamina) | Caused by obstruction of the sweat ducts close to the surface of the skin (in the stratum corneum of the epidermis); 1–2 millimeter (mm) superficial, clear blisters that break easily (leaving a bran-like scale) and can look like beads of sweat; no inflammation; widely spread blisters on the head, neck, and upper trunk |
Miliaria Rubra | Caused by obstruction of the sweat ducts in the deeper layers of the skin (mid-epidermis); most common form of heat rash; 2–4 mm, non-follicular (within the skin but not associated with a hair follicle) papules (small, solid bumps) and papulovesicles (small blisters resulting from papules); background skin redness in lighter skin tones, may darker than the surrounding skin in darker skin tones; involves the trunk, skinfolds of the neck, armpits, or groin (particularly in areas where there is friction from clothing); very itchy; the appearance of miliaria pustulosa, a variant of miliaria rubra, with pustules (small, pus-filled bumps or sores) |
Miliaria Profunda (Tropical Anhidrosis) | Caused by sweat leaking from the sweat glands into the middle layer of skin (blockage is at or below the dermoepidermal junction) after repeated episodes of miliaria rubra; 1–3 mm, asymptomatic, deep, skin-colored papules on the trunk and extremities |
More generally, heat rash looks like small, raised spots, possibly with mild swelling, that may be pink in lighter skin tones or darker than the surrounding skin in darker skin tones. It may also look like small bumps filled with clear or milky fluid.
Reproduced with permission from ©DermNet www.dermnetnz.org 2023.
Location on Infants
Heat rash in babies or children typically appears on areas such as:
- Buttocks/diaper area
- Chest/trunk
- Face
- Neck
- Skinfolds
- Thighs
- Typically sweaty areas
- Upper back
Symptom Onset and Duration
Heat rash usually clears up within three days after changing to a cooler environment.
Symptoms can be caused or affected by factors such as:
- Hot or humid weather/environment
- Exercise or intense physical activity
- Ointments that can block off sweat glands
- Blocking the skin with nonporous dressings or synthetic clothing against the skin
- Prolonged lying on waterproofed mattresses or mattress protectors
- Fever
On Different Skin Tones
On lighter skin tones, the rash typically looks red.
On darker skin tones, the rash may look gray, white, or slightly darker than surrounding skin.
When to See a Healthcare Provider
Heat rash doesn’t usually require medical care, but occasionally complications can arise. The symptoms can also be similar to more serious conditions, so it’s best to see a healthcare provider if you aren’t sure it is heat rash, particularly if other symptoms are present.
Contact your healthcare provider if your child’s rash is not gone after three days, or if you have questions or concerns.
Symptoms that warrant prompt medical attention may include:
- Increased pain, warmth, redness or discoloration, or swelling around the affected area
- Fever
- Worsening rash
- Sore throat, body aches, swollen lymph nodes (glands), or other symptoms that suggest illness or are unexplained
- When the child looks or acts very sick
- When you feel an urgent need for your child to be seen
While less common, rashes can indicate something serious, such as meningitis or a severe allergic reaction. Call 911 (or your local emergency number), or go to the emergency room if your child has a rash and symptoms such as:
- Stiff neck
- Sensitivity to/bothered by light
- A high temperature
- Confusion
- A rash that looks like small bruises or bleeding under the skin that does not fade when a glass is pressed against it (on darker skin tones, it may be easier to see the rash or color changes on the palms, soles of the feet, lips, tongue, and inside the eyelids)
- Pale, blue, gray, or blotchy skin, lips, or tongue
- Difficulty breathing (breathlessness, breathing very fast, grunting noises, or their tummy sucking in under their ribs)
- Seizure
- When you think your child needs emergency medical attention
How Baby Heat Rash Feels
Heat rash may have sensations like:
- Itching
- Prickly, pins-and-needles, feeling
Is It Baby Heat Rash or Something Else?
Baby rashes are common, and it can be difficult to know what the rash is. Only a healthcare provider can diagnose the rash, but it can be helpful to have a general idea of some rashes that babies and children can develop.
Rashes With Fever
Rashes with a high temperature could include:
- Fifth disease (slapped cheek syndrome): Rash on one or both cheeks, sore throat, runny nose, headache
- Hand, foot, and mouth disease: Blisters on hands and/or feet, ulcers in the mouth
- Scarlet fever: Rash of small raised bumps that feels rough (like sandpaper)
- Measles: Rash that is spotty, appears on the head or neck, and spreads to the rest of the body
Rashes With Itching
Rashes with itching may include:
- Eczema: Dry, thickened, scaly, cracked, or rough skin, itchy rash, and/or tiny red or discolored bumps that may blister, ooze, or become infected. The rash usually appears on the baby’s forehead, cheeks, or scalp, but it can be on the arms, legs, chest, or other areas.
- Contact dermatitis: Rash caused by a reaction from skin coming into contact with something the baby is allergic or sensitive to (such as laundry detergents or metallic snaps on clothing)
- Hives: Could be caused by an allergic reaction. Symptoms can include raised, itchy patches/spots—call 911 if there is swelling around the mouth or difficulty breathing
- Ringworm: Dry, itchy, ring-shaped or round patch of skin that might look pink, red, silver, or darker than surrounding skin
- Chickenpox: Small, itchy blisters that scab over
- Impetigo: Blisters or sores (can be itchy) that burst and leave behind crusty golden-brown patches
- Scabies: Tiny mites burrowing into the skin. Symptoms can include small, very itchy, raised spots. It may be raised lines with a dot at one end, often appearing between the fingers
Rashes Without Itching or Fever
Rashes that are not accompanied by itching or fever could include:
- Milia: Very tiny spots (white or yellow on lighter skin tones, may be faint blue on darker skin tones) on a newborn’s face that go away on their own without treatment
- Erythema toxicum: Raised spots that are red, yellow, or white on lighter skin and may be brown, purple, or gray on darker skin; appears on newborns, usually on face, body, upper arms, or thighs; may come and go, but gets better on its own without treatment
- Molluscum contagiosum: Small, firm, raised spots that are the same color or darker than surrounding skin, or are pink
- Diaper rash: Painful rash in diaper area, particularly buttocks, red in lighter skin tones, may be purplish or darker brown in darker skin tones
- Baby acne: Pimples/spots on baby’s nose, cheeks, or forehead, within a month of being born; goes away on its own
Complications of Heat Rash
Complications from heat rash are rare, but may include:
- Infection: Bacteria makes the fluid-filled bumps grow bigger, become more inflamed, and become painful.
- Heat exhaustion and heat stroke: Clogged sweat glands can prevent the body from cooling itself properly and lead to heat exhaustion. If heat exhaustion isn’t treated, it could progress to heat stroke, which is dangerous and potentially fatal.
How to Treat Your Baby’s Heat Rash
Heat rash usually clears up on its own in a few days, but there are things you can do to help your baby feel more comfortable while it heals.
Keep Cool
To help your baby stay cool:
- Keep your home cool and well-ventilated.
- Use air-conditioning if possible, or turn on fans.
- Give your child enough age-appropriate fluids to stay hydrated.
Get Wet
You may want to try the following:
- Bathing your child in lukewarm water without soap (for 10 minutes three or more times a day for large rashes)
- Letting them air-dry after bathing instead of using a towel
- Putting a cool (not cold), wet washcloth on a small rash for five to 10 minutes, then letting the area air-dry
Dress Light
For children older than 1 year, sleeping on a cotton towel might help absorb sweat.
Remove their clothes as often as possible, and loosen their diaper if it is rubbing against the rash.
Go light on the clothing, both in weight and color, and use lightweight bedding.
Skip the Lotions, Oils, and Ointments
Ointments, oils, and lotions can block sweat glands and should be avoided unless directed by your healthcare provider.
To help with itching, your healthcare provider may suggest:
Dressing Your Baby With Heat Rash
Overdressing your baby can cause them to overheat, leading to heat rash. Babies can have hands and feet that are cool to the touch, but they should be dressed to the same comfort level as you are for the same temperature and activity level.
If it is warm, choose clothing that is:
- Cotton
- Light in color
- Lightweight
- Loose-fitting
- Single-layer
Skin-to-Skin Contact
Breastfeeding babies may get a rash on their face from being held against their nursing parent’s skin, or from lanolin used on nipples which can block sweat glands.
Are Heat Rashes in Babies Avoidable?
Heat rash can’t always be avoided, but some measures can help reduce the risk. These practices are similar to the ones used to treat heat rash, including:
- Keep your baby cool with air-conditioning or a gentle breeze from a fan.
- Dress your baby comfortably for the weather, such as lightweight cotton clothing in hot weather.
- Avoid ointments, lotions, and powders (they don’t prevent or treat heat rash and can make it worse).
- Change wet or soiled diapers right away.
Summary
Heat rash is caused by blocked sweat glands trapping sweat. It is common in babies and children. Heat rash can cause symptoms such as raised bumps that may be fluid-filled, and reddened or discolored skin. The rash can be itchy or cause a prickly, pins-and-needles feeling.
Heat rash can be treated and prevented by keeping your child appropriately cool by dressing them lightly in the heat, bringing them to a cool environment, and giving them cool baths.
Heat rash is typically not serious, but it can share similar symptoms to more concerning conditions. Talk to a healthcare provider if your child has symptoms you are curious or concerned about.