Skin & Rashes

Heat Rash (Miliaria) in Newborns

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

Content reviewed against published AAP, Mayo Clinic guidelines

Editorial policy

Last reviewed:

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

The short answer

Heat rash (miliaria) in newborns appears as tiny red bumps or clear blisters, usually in skin folds, on the face, neck, chest, or areas covered by clothing. It occurs when sweat glands become blocked from overheating or overdressing. It is harmless and resolves quickly once baby is cooled down.

Key takeaways

  • Heat rash (miliaria) in newborns appears as tiny red bumps or clear blisters, usually in skin folds, on the face, neck, chest, or areas covered by clothing. It occurs when sweat glands become blocked from overheating or overdressing. It is harmless and resolves quickly once baby is cooled down.
  • Usually normal when: Tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing
  • Call your doctor if: Rash accompanied by fever, which could indicate infection rather than heat rash
  • 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)

This is one of the most common questions parents ask. Searching for answers means you care.

What Parents Should Know

According to AAP, Mayo Clinic guidelines, heat rash (miliaria) in newborns appears as tiny red bumps or clear blisters, usually in skin folds, on the face, neck, chest, or areas covered by clothing. It occurs when sweat glands become blocked from overheating or overdressing. It is harmless and resolves quickly once baby is cooled down. At 0-1 month, newborns are prone to heat rash because their sweat glands are immature. The rash appears as tiny red bumps (miliaria rubra) or tiny clear blisters (miliaria crystallina) in areas where sweat is trapped: neck folds, chest, back, diaper area, and anywhere clothing is tight. Treatment is simple: cool your baby down, remove excess clothing, and move to a cooler environment. Avoid heavy creams or lotions that can block pores. Dress your baby in one layer more than you would wear, not multiple extra layers. It is generally considered normal when tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing. However, you should contact your pediatrician promptly if rash accompanied by fever, which could indicate infection rather than heat rash.

Sources: [1], [2]

Normal vs. Concerning

Usually Normal
Worth Discussing
Tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing
Rash accompanied by fever, which could indicate infection rather than heat rash
Rash resolves quickly (within hours) after cooling down
Signs of overheating: hot to touch, rapid breathing, lethargy, or unresponsiveness
Baby is not bothered by the rash
Heat rash does not resolve within a day or two after cooling measures
No spreading redness, pus, or fever
The rash looks different from typical heat rash (spreading, raised, painful)

By Age

What to expect by age

0-1 month

Newborns are prone to heat rash because their sweat glands are immature. The rash appears as tiny red bumps (miliaria rubra) or tiny clear blisters (miliaria crystallina) in areas where sweat is trapped: neck folds, chest, back, diaper area, and anywhere clothing is tight. Treatment is simple: cool your baby down, remove excess clothing, and move to a cooler environment. Avoid heavy creams or lotions that can block pores. Dress your baby in one layer more than you would wear, not multiple extra layers.

1-3 months

Heat rash remains common during this period. As you learn your baby's temperature regulation needs, you will become better at dressing them appropriately. The rash resolves within hours to a day once overheating is addressed. Keep the nursery at a comfortable temperature (68-72F).

3-6 months

Heat rash may occur during warmer months or when babies are overdressed. The same cooling measures apply. Avoid direct sun exposure and dress your baby in light, breathable fabrics.

6-12 months

As your baby becomes more active, heat rash may occur in areas of increased friction or sweating. Continue to dress appropriately for the temperature and keep skin folds dry.

What to Tell Your Pediatrician

  • Describe when you first noticed heat rash (miliaria) in newborns and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if heat rash does not resolve within a day or two after cooling measures.
  • Mention if the rash looks different from typical heat rash (spreading, raised, painful).
  • 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 or clear blisters in skin folds or under clothing that appear during warm weather or overdressing
  • Rash resolves quickly (within hours) after cooling down
  • Baby is not bothered by the rash
  • No spreading redness, pus, or fever
Mention at your next visit when...
  • Heat rash does not resolve within a day or two after cooling measures
  • The rash looks different from typical heat rash (spreading, raised, painful)
  • You are unsure whether the rash is heat rash or something else
Act now when...
  • Rash accompanied by fever, which could indicate infection rather than heat rash
  • Signs of overheating: hot to touch, rapid breathing, lethargy, or unresponsiveness

What You Can Do at Home

  • Keep track of when you notice heat rash (miliaria) in newborns — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing — this is generally within the range of normal.
  • At 0-1 month, 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 rash accompanied by fever, which could indicate infection rather than heat rash.

Overdressing and Overheating Baby

Overdressing and overheating are common concerns and a risk factor for SIDS. Dress your baby in one layer more than you would wear comfortably. Signs of overheating include sweating, damp hair, flushed cheeks, heat rash, and rapid breathing. Check your baby's chest or back of neck to gauge temperature.

Ideal Room Temperature for Baby

The ideal room temperature for a sleeping baby is between 68-72 degrees F (20-22 degrees C). A room that is too warm increases the risk of SIDS. Dress your baby in one layer more than you would wear comfortably, and check their chest or back of neck to assess temperature rather than hands or feet.

Erythema Toxicum (Red Blotchy Rash in Newborns)

Erythema toxicum is a very common, completely harmless rash that appears in up to 50% of full-term newborns, usually within the first 2-5 days of life. It looks like red blotches with small yellow or white bumps and can appear anywhere on the body except the palms and soles. It resolves on its own without any treatment.

Triage

Rash Decision Tree

Identify common rashes and determine when to seek care.

Guide

Baby Skin Conditions Guide

Visual guide to common baby skin conditions, rashes, and when to see a doctor.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

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 heat rash (miliaria) in newborns normal?
Heat rash (miliaria) in newborns appears as tiny red bumps or clear blisters, usually in skin folds, on the face, neck, chest, or areas covered by clothing. It occurs when sweat glands become blocked from overheating or overdressing. It is harmless and resolves quickly once baby is cooled down.
When should I call the doctor about heat rash (miliaria) in newborns?
Rash accompanied by fever, which could indicate infection rather than heat rash Signs of overheating: hot to touch, rapid breathing, lethargy, or unresponsiveness
When is heat rash (miliaria) in newborns normal?
Tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing Rash resolves quickly (within hours) after cooling down Baby is not bothered by the rash
What causes heat rash (miliaria) in newborns?
Heat rash (miliaria) in newborns appears as tiny red bumps or clear blisters, usually in skin folds, on the face, neck, chest, or areas covered by clothing. It occurs when sweat glands become blocked from overheating or overdressing. It is harmless and resolves quickly once baby is cooled down. Common explanations include: Tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing. Rash resolves quickly (within hours) after cooling down.
What should I mention to my pediatrician about heat rash (miliaria) in newborns?
You should mention heat rash (miliaria) in newborns at your next visit if: Heat rash does not resolve within a day or two after cooling measures. The rash looks different from typical heat rash (spreading, raised, painful). You are unsure whether the rash is heat rash or something else.
Is heat rash (miliaria) in newborns normal at 0-1 month?
Newborns are prone to heat rash because their sweat glands are immature. The rash appears as tiny red bumps (miliaria rubra) or tiny clear blisters (miliaria crystallina) in areas where sweat is trapped: neck folds, chest, back, diaper area, and anywhere clothing is tight. Treatment is simple: cool your baby down, remove excess clothing, and move to a cooler environment. Avoid heavy creams or lotions that can block pores. Dress your baby in one layer more than you would wear, not multiple extra layers.
Is heat rash (miliaria) in newborns normal at 1-3 months?
Heat rash remains common during this period. As you learn your baby's temperature regulation needs, you will become better at dressing them appropriately. The rash resolves within hours to a day once overheating is addressed. Keep the nursery at a comfortable temperature (68-72F).
Should I go to the ER for heat rash (miliaria) in newborns?
Seek emergency care if rash accompanied by fever, which could indicate infection rather than heat rash, or if signs of overheating: hot to touch, rapid breathing, lethargy, or unresponsiveness. When in doubt, call your pediatrician's after-hours line for guidance.
Does heat rash (miliaria) in newborns go away on its own?
In many cases, heat rash (miliaria) in newborns resolves on its own, especially when tiny red bumps or clear blisters in skin folds or under clothing that appear during warm weather or overdressing. By 6-12 months, as your baby becomes more active, heat rash may occur in areas of increased friction or sweating. Continue to dress appropriately for the temperature and keep skin folds dry.
AAPMAYO CLINIC

References

  1. [1]American Academy of Pediatrics. Heat Rash. HealthyChildren.org. AAP
  2. [2]Mayo Clinic. Heat Rash. Patient Care and Health Information. Mayo Clinic

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Heat Rash (Miliaria) in Newborns.

Things to mention

  • Describe when you first noticed heat rash (miliaria) in newborns and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if heat rash does not resolve within a day or two after cooling measures.
  • Mention if the rash looks different from typical heat rash (spreading, raised, painful).
  • 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

  • Heat rash does not resolve within a day or two after cooling measures
  • The rash looks different from typical heat rash (spreading, raised, painful)
  • You are unsure whether the rash is heat rash or something else

Urgent signs to report immediately

  • Rash accompanied by fever, which could indicate infection rather than heat rash
  • Signs of overheating: hot to touch, rapid breathing, lethargy, or unresponsiveness

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 heat rash (miliaria) in newborns are normal. Talk to your pediatrician if rash accompanied by fever, which could indicate infection rather than heat rash.

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

Share:FacebookX

Was this page helpful?

Related Skin Concerns

Overdressing and Overheating Baby

Overdressing and overheating are common concerns and a risk factor for SIDS. Dress your baby in one layer more than you would wear comfortably. Signs of overheating include sweating, damp hair, flushed cheeks, heat rash, and rapid breathing. Check your baby's chest or back of neck to gauge temperature.

Ideal Room Temperature for Baby

The ideal room temperature for a sleeping baby is between 68-72 degrees F (20-22 degrees C). A room that is too warm increases the risk of SIDS. Dress your baby in one layer more than you would wear comfortably, and check their chest or back of neck to assess temperature rather than hands or feet.

Erythema Toxicum (Red Blotchy Rash in Newborns)

Erythema toxicum is a very common, completely harmless rash that appears in up to 50% of full-term newborns, usually within the first 2-5 days of life. It looks like red blotches with small yellow or white bumps and can appear anywhere on the body except the palms and soles. It resolves on its own without any treatment.

My Baby Has an Extra Nipple (Accessory Nipple)

Accessory (supernumerary) nipples are one of the most common minor congenital findings, occurring in about 1 in 18 people. They appear as small, flat, often pigmented bumps along the "milk line" — an embryonic line running from the armpit to the groin on each side. Most people mistake them for moles. Accessory nipples are almost always harmless and require no treatment. In rare cases, they may be associated with kidney abnormalities, so some pediatricians recommend a renal ultrasound if one is found, though this practice varies.

My Baby Was Born with a Raw Spot on Their Scalp (Aplasia Cutis)

Aplasia cutis congenita (ACC) is a condition where a baby is born with a small area of missing skin, most commonly on the scalp. It occurs in about 1 in 10,000 births. The affected area may look like a raw wound, an ulcer, or may have already healed into a thin, shiny scar by the time of birth. Most cases are small, isolated, and heal well with basic wound care — the area eventually forms a hairless scar. Larger defects or those associated with other findings may need more investigation, but isolated small ACC has an excellent prognosis.

New Treatments for Atopic Dermatitis (Eczema) in Children

Treatment for atopic dermatitis in children has advanced significantly in recent years. While moisturizers and topical steroids remain first-line treatments, newer options include non-steroidal topical medications (like crisaborole), biologic therapies (like dupilumab, approved for children 6 months and older), and JAK inhibitors. Most children's eczema is well-managed with basic skin care and mild topical treatments, but these newer options provide hope for moderate-to-severe cases.