Skin & Rashes

Baby Heat Rash (Prickly Heat / Miliaria)

Medically reviewed by Dr. Sarah Chen, MD, FAAP · Board-Certified Pediatrician

Content reviewed against published AAP, AAP, CDC guidelines

Editorial policy

Last reviewed:

Baby skin is sensitive and changes frequently. If you are noticing baby heat rash (prickly heat / miliaria), here is what you need to know.

The short answer

Heat rash happens when sweat gets trapped under your baby's skin, causing tiny red bumps or blisters, usually in skin folds or areas covered by clothing. It is harmless and clears up quickly once your baby is cooled down. Dressing your baby in one layer more than you would wear is a good rule of thumb to prevent overheating.

Key takeaways

  • Heat rash happens when sweat gets trapped under your baby's skin, causing tiny red bumps or blisters, usually in skin folds or areas covered by clothing. It is harmless and clears up quickly once your baby is cooled down. Dressing your baby in one layer more than you would wear is a good rule of thumb to prevent overheating.
  • Usually normal when: Tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing
  • Call your doctor if: The rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection
  • Varies by age — see the age-by-age breakdown below
“Eczema is very common in babies and children. About 1 in 10 children will develop eczema, typically starting in the first few months of life.”
— Eczema in Babies and Children, American Academy of Pediatrics (AAP)

Thousands of parents search for this exact thing. You are not alone.

What Parents Should Know

According to AAP, CDC guidelines, heat rash happens when sweat gets trapped under your baby's skin, causing tiny red bumps or blisters, usually in skin folds or areas covered by clothing. It is harmless and clears up quickly once your baby is cooled down. Dressing your baby in one layer more than you would wear is a good rule of thumb to prevent overheating. At 0-3 months, newborns are especially prone to heat rash because their sweat glands are not fully developed. It often appears on the neck, chest, groin folds, and armpits. Well-meaning parents sometimes overdress newborns, which is a very common cause. A good guide is to dress your baby in one more layer than you are comfortable in. It is generally considered normal when tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing. However, you should contact your pediatrician promptly if the rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing
The rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection
The rash clears up within a few hours to a day once your baby cools down
Your baby has a fever along with a rash and seems unwell, as this may indicate a different type of rash that needs evaluation
Small clear or white blisters on the skin surface that do not seem to bother your baby
The heat rash does not improve within 2-3 days even after keeping your baby cool and dry
Rash that comes and goes with temperature and clothing changes
The bumps seem to be getting larger, more red, or more swollen

By Age

What to expect by age

0-3 months

Newborns are especially prone to heat rash because their sweat glands are not fully developed. It often appears on the neck, chest, groin folds, and armpits. Well-meaning parents sometimes overdress newborns, which is a very common cause. A good guide is to dress your baby in one more layer than you are comfortable in.

3-6 months

Heat rash commonly appears in the folds of the neck where drool and sweat collect, and in the creases of chubby arms and legs. In warm weather, choose loose, breathable cotton clothing and keep indoor temperatures comfortable. A lukewarm bath can provide quick relief from a heat rash flare.

6-12 months

As babies become more active and mobile, they generate more body heat. Heat rash may appear after active play, being in a car seat for an extended period, or wearing a carrier. Removing layers, moving to a cooler environment, and allowing air to reach the affected skin usually resolves it within hours.

12 months+

Toddlers are busy and active, making heat rash during warm months fairly common. It is especially likely in the diaper area, behind the knees, and in elbow creases. As your child's sweat glands mature, heat rash tends to become less frequent. Keeping them hydrated and dressed in breathable fabrics helps.

What to Tell Your Pediatrician

  • Describe when you first noticed baby heat rash (prickly heat / miliaria) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if the heat rash does not improve within 2-3 days even after keeping your baby cool and dry.
  • Mention if the bumps seem to be getting larger, more red, or more swollen.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing
  • The rash clears up within a few hours to a day once your baby cools down
  • Small clear or white blisters on the skin surface that do not seem to bother your baby
  • Rash that comes and goes with temperature and clothing changes
Mention at your next visit when...
  • The heat rash does not improve within 2-3 days even after keeping your baby cool and dry
  • The bumps seem to be getting larger, more red, or more swollen
  • Your baby is scratching intensely at the rash or seems unusually fussy
Act now when...
  • The rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection
  • Your baby has a fever along with a rash and seems unwell, as this may indicate a different type of rash that needs evaluation

What You Can Do at Home

  • Keep track of when you notice baby heat rash (prickly heat / miliaria) — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing — this is generally within the range of normal.
  • At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Use fragrance-free, hypoallergenic products on your baby's skin. Avoid over-bathing — 2-3 baths per week is usually sufficient.
  • While monitoring at home, seek immediate care if the rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection.

Baby Rash in Skin Folds - Neck, Armpits, and Creases

Rashes in baby's skin folds (neck, armpits, groin, behind ears, elbow and knee creases) are extremely common because these warm, moist areas trap moisture from drool, spit-up, sweat, and milk. The medical term is intertrigo. Most fold rashes respond to keeping the area clean and dry. If the rash is bright red, has satellite spots, or has a yeasty smell, it may have developed a yeast (candida) infection and need antifungal treatment. Keeping folds dry is both the treatment and prevention.

Baby Chin Rash from Drooling

Drool rash is extremely common and appears as red, irritated, or slightly bumpy skin on the chin, cheeks, neck, and chest where drool sits. It is caused by the constant moisture and digestive enzymes in saliva irritating the skin. Keeping the area dry and applying a barrier like petroleum jelly before drool exposure is the most effective treatment.

Baby Rash Around the Mouth - Drool Rash and Other Causes

A rash around your baby's mouth is most commonly drool rash (contact irritant dermatitis from constant moisture). Drool rash looks like red, slightly rough, chapped skin around the mouth, chin, and cheeks. It is very common during teething when drool production increases dramatically. Other causes include food contact irritation (especially from acidic foods like tomato and citrus), pacifier friction, eczema, and occasionally hand-foot-and-mouth disease. True food allergies typically cause hives or swelling, not a flat red rash.

Raised Bumps on Baby's Skin

Raised bumps on a baby's skin have many possible causes, most of which are harmless. Common causes include keratosis pilaris (tiny rough bumps on upper arms and thighs), molluscum contagiosum (small, dome-shaped, pearl-like bumps from a viral infection), insect bites, viral rashes, and milia (tiny white bumps in newborns). The bumps' appearance - their color, size, texture, location, and whether they are itchy - helps determine the cause. Most resolve on their own or with simple treatment.

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Month-by-Month Development

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When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is baby heat rash (prickly heat / miliaria) normal?
Heat rash happens when sweat gets trapped under your baby's skin, causing tiny red bumps or blisters, usually in skin folds or areas covered by clothing. It is harmless and clears up quickly once your baby is cooled down. Dressing your baby in one layer more than you would wear is a good rule of thumb to prevent overheating.
When should I call the doctor about baby heat rash (prickly heat / miliaria)?
The rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection Your baby has a fever along with a rash and seems unwell, as this may indicate a different type of rash that needs evaluation
When is baby heat rash (prickly heat / miliaria) normal?
Tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing The rash clears up within a few hours to a day once your baby cools down Small clear or white blisters on the skin surface that do not seem to bother your baby
What causes baby heat rash (prickly heat / miliaria)?
Heat rash happens when sweat gets trapped under your baby's skin, causing tiny red bumps or blisters, usually in skin folds or areas covered by clothing. It is harmless and clears up quickly once your baby is cooled down. Dressing your baby in one layer more than you would wear is a good rule of thumb to prevent overheating. Common explanations include: Tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing. The rash clears up within a few hours to a day once your baby cools down.
What should I mention to my pediatrician about baby heat rash (prickly heat / miliaria)?
You should mention baby heat rash (prickly heat / miliaria) at your next visit if: The heat rash does not improve within 2-3 days even after keeping your baby cool and dry. The bumps seem to be getting larger, more red, or more swollen. Your baby is scratching intensely at the rash or seems unusually fussy.
Is baby heat rash (prickly heat / miliaria) normal at 0-3 months?
Newborns are especially prone to heat rash because their sweat glands are not fully developed. It often appears on the neck, chest, groin folds, and armpits. Well-meaning parents sometimes overdress newborns, which is a very common cause. A good guide is to dress your baby in one more layer than you are comfortable in.
Is baby heat rash (prickly heat / miliaria) normal at 3-6 months?
Heat rash commonly appears in the folds of the neck where drool and sweat collect, and in the creases of chubby arms and legs. In warm weather, choose loose, breathable cotton clothing and keep indoor temperatures comfortable. A lukewarm bath can provide quick relief from a heat rash flare.
Should I go to the ER for baby heat rash (prickly heat / miliaria)?
Seek emergency care if the rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection, or if your baby has a fever along with a rash and seems unwell, as this may indicate a different type of rash that needs evaluation. When in doubt, call your pediatrician's after-hours line for guidance.
Does baby heat rash (prickly heat / miliaria) go away on its own?
In many cases, baby heat rash (prickly heat / miliaria) resolves on its own, especially when tiny red bumps in skin folds, on the neck, or under clothing that appear during warm weather or after overdressing. By 12 months+, toddlers are busy and active, making heat rash during warm months fairly common. It is especially likely in the diaper area, behind the knees, and in elbow creases. As your child's sweat glands mature, heat rash tends to become less frequent. Keeping them hydrated and dressed in breathable fabrics helps.
AAPAAPCDC

References

  1. [1]American Academy of Pediatrics. Heat Rash. HealthyChildren.org. AAP
  2. [2]American Academy of Pediatrics. Dressing Your Baby for the Weather. HealthyChildren.org. AAP
  3. [3]Centers for Disease Control and Prevention. Warning Signs and Symptoms of Heat-Related Illness. CDC

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Baby Heat Rash (Prickly Heat / Miliaria).

Things to mention

  • Describe when you first noticed baby heat rash (prickly heat / miliaria) and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if the heat rash does not improve within 2-3 days even after keeping your baby cool and dry.
  • Mention if the bumps seem to be getting larger, more red, or more swollen.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • The heat rash does not improve within 2-3 days even after keeping your baby cool and dry
  • The bumps seem to be getting larger, more red, or more swollen
  • Your baby is scratching intensely at the rash or seems unusually fussy

Urgent signs to report immediately

  • The rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection
  • Your baby has a fever along with a rash and seems unwell, as this may indicate a different type of rash that needs evaluation

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Baby Skin Conditions GuideRash TriageBaby Tracker

Bottom line

Most cases of baby heat rash (prickly heat / miliaria) are normal. Talk to your pediatrician if the rash develops pus-filled bumps, red streaks, or warm swollen areas, which may indicate a secondary infection.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Related Skin Concerns

Baby Rash in Skin Folds - Neck, Armpits, and Creases

Rashes in baby's skin folds (neck, armpits, groin, behind ears, elbow and knee creases) are extremely common because these warm, moist areas trap moisture from drool, spit-up, sweat, and milk. The medical term is intertrigo. Most fold rashes respond to keeping the area clean and dry. If the rash is bright red, has satellite spots, or has a yeasty smell, it may have developed a yeast (candida) infection and need antifungal treatment. Keeping folds dry is both the treatment and prevention.

Baby Chin Rash from Drooling

Drool rash is extremely common and appears as red, irritated, or slightly bumpy skin on the chin, cheeks, neck, and chest where drool sits. It is caused by the constant moisture and digestive enzymes in saliva irritating the skin. Keeping the area dry and applying a barrier like petroleum jelly before drool exposure is the most effective treatment.

Baby Rash Around the Mouth - Drool Rash and Other Causes

A rash around your baby's mouth is most commonly drool rash (contact irritant dermatitis from constant moisture). Drool rash looks like red, slightly rough, chapped skin around the mouth, chin, and cheeks. It is very common during teething when drool production increases dramatically. Other causes include food contact irritation (especially from acidic foods like tomato and citrus), pacifier friction, eczema, and occasionally hand-foot-and-mouth disease. True food allergies typically cause hives or swelling, not a flat red rash.

Raised Bumps on Baby's Skin

Raised bumps on a baby's skin have many possible causes, most of which are harmless. Common causes include keratosis pilaris (tiny rough bumps on upper arms and thighs), molluscum contagiosum (small, dome-shaped, pearl-like bumps from a viral infection), insect bites, viral rashes, and milia (tiny white bumps in newborns). The bumps' appearance - their color, size, texture, location, and whether they are itchy - helps determine the cause. Most resolve on their own or with simple treatment.

Baby Rash That Won't Go Away

A rash that persists for more than 2 weeks or keeps recurring likely needs evaluation beyond "wait and see." The most common causes of persistent rashes in babies include eczema (dry, itchy, patches), fungal infections (especially in skin folds), contact dermatitis (reaction to a product), and less commonly, psoriasis or autoimmune conditions. Proper identification is important because the treatment differs significantly - using the wrong cream (like steroid cream on a fungal infection) can actually make things worse.

Baby Eczema (Atopic Dermatitis)

Baby eczema is extremely common, affecting up to 20% of infants, and is not caused by anything you did wrong. It shows up as dry, red, itchy patches and is very manageable with consistent moisturizing and gentle skin care. Most children outgrow it by school age.