A damp head after a feed or a nap is one of the first things many new parents notice, and it often leads to one question: when do babies start sweating?
Research suggests that most babies born at 36 weeks of pregnancy or later can sweat from their first day, while babies born earlier usually develop the ability within about two weeks.
Early sweating is light, shows up mainly on the forehead, and keeps changing all the way to puberty.
In this post, you will learn what the research shows at each age, where babies sweat first, how to tell normal sweating from a sign of overheating, and which symptoms mean it is time to call your paediatrician.
Key takeaways
- Most babies born at 36 weeks or later can sweat from day one, starting on the forehead.
- Babies born before 36 weeks usually begin sweating within about two weeks of birth.
- A baby can overheat without sweating much, so check the chest or the back of the neck.
- Heavy sweating with fast breathing, tiring during feeds, or poor weight gain needs a paediatrician’s check.
When Do Newborns First Develop Functional Sweat Glands?
Do newborns sweat? Yes. Babies are born with eccrine sweat glands, the type that cools the body, and most full-term newborns can use them from the first day of life.
The response is small and slow, which is why newborn sweating usually looks like slight dampness on the forehead rather than visible drops.
The clearest evidence comes from a 1982 preterm sweating study in The Journal of Paediatrics, which tested 85 term and preterm babies.
Most babies born at 36 weeks or later could sweat from their first day when they were warmed, and the sweat appeared first and most strongly on the forehead.
Newborn sweat glands also produce much less than an adult’s.
A 1969 study in The Journal of Physiology found that the peak output of each newborn gland was about three times lower than the highest rate recorded in adults.
Newborn sweating is real but limited, which helps explain why young babies depend so much on the adults dressing them.
When Do Babies Start Sweating? Timeline From Birth Through Puberty
Babies can sweat from birth or within about two weeks of it, depending on how early they were born. What changes after that is how much they sweat and where.
Output per sweat gland stays below adult levels through childhood and rises during puberty, when the adult pattern of torso and underarm sweating develops.
| Age | What the research shows |
| Born before 36 weeks | No heat sweating at first. In the 1982 study, every baby studied could sweat by 13 days after birth. |
| Born at 36 weeks or later, first day | Most can sweat when warm, mainly on the forehead, in small amounts. |
| First weeks of life | Sweating starts at a lower body temperature and covers more skin as the days pass. |
| Infancy through late childhood | Sweating works, but each gland produces less sweat than an adult’s gland. |
| Puberty | Output per gland rises, underarm glands become active, and torso sweating increases. |
The gap with adults lasts much longer. A 1997 study in the European Journal of Applied Physiology found that 10- and 11-year-old boys sweated less than young men during exercise in warm conditions, because each active gland produced less sweat.
More recently, a 2026 University of Southampton study of 28 girls aged 8 to 25 found that torso sweating became more adult-like at around age 14, while younger girls sweated most from their hands and feet.
When Do Premature Babies Start Sweating?
Babies born before 36 weeks usually cannot sweat at birth, but they catch up quickly.
In the 1982 study, life outside the womb sped up development so much that all the babies studied could sweat by 13 days old, no matter how early they were born.
The response is weaker at first. The same study found that the strength and spread of sweating depended on gestational age, and that more premature babies needed a warmer environment before they started to sweat.
The 1969 research found no heat sweating at all in babies younger than 210 days after conception, which is about 30 weeks of pregnancy.
These studies are small and decades old, so treat the exact day counts as a guide rather than a rule.
For daily care, the AAP notes that a premature baby may need an extra layer of clothing until they reach the weight of a full-term baby. Your NICU team or paediatrician can tell you what fits your baby.
How Do Babies Regulate Their Body Temperature?
Babies can control their temperature, but with far less margin than adults. A newborn has a large skin surface compared with body weight, so heat moves in and out of the body quickly.
To stay warm, newborns rely on a special tissue called brown fat rather than shivering. Because their ability to shiver is limited, burning brown fat is their main way to produce heat.
To cool down, the body uses sweat, which carries heat away as it dries on the skin. Since each infant gland produces so little, clothing does much of the work.
The AAP suggests that a baby in hot weather above 75°F can wear a single layer, and our guide to dressing your baby for weather covers how to adjust layers through the seasons.
Where Do Babies Sweat First?
A baby’s head sweating is usually the first sign parents see. The 1969 research found that sweat appeared first on the forehead and temples, then on the chest, and later on the legs.
A 1979 study of term newborns in Archives of Disease in Childhood also found that sweating most often began on the forehead, although it reached the trunk and limbs too.
That same study found no heat-related sweating on the palms or soles. Those areas sweat in response to emotion instead.
A 1982 study of emotional sweating found that babies born at 37 weeks or later show palm sweating linked to arousal from the day of birth, while earlier babies develop it at the equivalent of 36 to 37 weeks of pregnancy.
How Can You Tell if Your Baby Is Sweating Normally?
Normal baby sweating is mild and shows up mostly on the head, neck or back.
It happens during sleep, feeding, crying or in a warm room, and your baby otherwise seems content and feeds well. It does not soak through clothing.
To check whether your baby is too warm, feel the chest or the back of the neck rather than the hands and feet.
The AAP lists sweating, a hot chest and flushed skin as signs of overheating. Flushing has other causes as well, which we explain in our post on why baby cheeks turn red.
Since the sweat response is limited in early infancy, a baby can get too warm before much sweat appears. Checking the skin and the room is more reliable than waiting for visible sweat.
Why Is My Baby Sweating While Sleeping?
Baby sweating while sleeping is common and usually harmless.
Children’s Hospital of Philadelphia notes that many children sweat while they sleep, and the forehead and scalp are where infant sweating is strongest, so damp hair after a nap is expected.
The most common fixable cause is too much warmth. The AAP’s 2022 sleep recommendations advise dressing a baby in no more than one layer more than an adult would wear to feel comfortable in that room, and avoiding head coverings indoors.
This matters for safety as well as comfort, because the AAP links overheating to a higher risk of sudden infant death syndrome (SIDS).
Keep loose blankets, pillows and bumpers out of the crib. If your baby needs extra warmth, a wearable blanket is a safer choice than a loose one.
Why Does My Baby Sweat While Feeding?
Mild sweating during feeds is common. Sucking takes effort, and being held close adds body heat, so a damp head and neck during a feed is a normal response.
It becomes a concern when it comes with other signs.
Children’s Hospital of Philadelphia lists getting sweaty with feeds and getting out of breath with feeds among the infant heart problem warning signs, while also noting that most children with these symptoms do not have a heart problem.
If your baby sweats heavily at most feeds and also gets tired quickly, takes unusually long to finish, breathes fast or gains weight slowly, ask your paediatrician to check them promptly.
What Causes Excessive Sweating in Babies?
Most heavy sweating in babies has an everyday cause, although a few medical causes are worth ruling out.
1.Warm Environment
Heat is the most common cause. The AAP warns that a heat index of 90°F (32°C) or higher can be dangerous, especially for babies, so plan outings for cooler parts of the day.
Cars need extra care. The National Highway Traffic Safety Administration (NHTSA) explains that children’s bodies warm three to five times faster than adults’, and that a child can die in a hot car even on a 60°F day.
Never leave a baby alone in a vehicle, even for a minute.
2.Overdressing
Extra layers, thick fabrics or a hat worn indoors can trap heat even in a comfortable room. Use the chest or neck check described above, and remove a layer if your baby feels hot.
3.Fever
If your baby is sweating and feels hot or seems unwell, take their temperature with a thermometer.
The AAP guide to baby fevers says a rectal reading is the most reliable for young babies, and that a baby 3 months or younger with a rectal temperature of 100.4°F (38°C) or higher needs a call to the paediatrician right away.
Check with your paediatrician before giving a young baby any fever medicine.
4.Underlying Medical Conditions
Rarely, heavy sweating that heat, clothing or feeding effort cannot explain points to a medical issue.
Heart conditions are the best known, as described above.
Sweating and flushing on only one side of the body can reflect a problem with the nerves that control sweating, and Cleveland Clinic advises having it checked.
When Should You Call a Doctor About Baby Sweating?
Call your paediatrician soon if your baby has:
- Heavy sweating at most feeds, with slow feeding, tiring quickly or poor weight gain
- Heavy sweating in a cool room or while resting
- Sweating with persistent fast or noisy breathing
- Sweating with constant irritability or unusual paleness
- Sweating that keeps affecting only one side of the body
Call 911 or seek emergency care right away if your baby has:
- A bluish colour around the lips, mouth or face
- Trouble breathing, with flaring nostrils or skin pulling in around the ribs
- Unusual drowsiness or difficulty waking
- A rectal temperature of 100.4°F (38°C) or higher when 3 months or younger
- Hot skin and seems unwell after time in the heat or in a car
How Can You Prevent Your Baby From Overheating?
Prevention comes down to a few habits you can repeat every day. Check the chest or neck whenever you are unsure, and adjust before your baby gets flushed or restless.
Dress by the one-extra-layer rule for both naps and outings, and take off hats and outer layers as soon as you come indoors or into a warm car.
On hot days, keep your baby in the shade or air conditioning during the warmest hours and watch the heat index.
What to Remember About Baby Sweating
So, when do babies start sweating? Most babies born at 36 weeks or later can sweat from their first day, and earlier babies usually catch up within about two weeks.
Sweating starts on the forehead, grows stronger over the first weeks, and stays below adult levels until puberty.
Light sweating on the head during sleep, feeds or crying is a typical part of how a small body handles heat.
Keep layers light, follow safe sleep guidance, and check the chest rather than the hands.
If heavy sweating comes with fast breathing, tiring feeds or slow weight gain, write down when it happens and share those notes with your paediatrician.
Frequently Asked Questions
Is It Normal for a Newborn to Sweat a Lot?
Some situations produce more sweat than parents expect. Crying triggers emotional sweating on the palms and soles, and the 1982 emotional sweating research found that by the third week, levels during vigorous crying were similar to those of an anxious adult. Sweaty hands during a crying spell are expected and settle once your baby calms down.
Can Babies Sweat From Their Armpits?
Babies have cooling sweat glands across most of their skin, so a little underarm dampness can happen. The underarm glands that cause body odour are different. According to KidsHealth, these glands become much more active during puberty and begin producing body odour then.
Is It Normal for a Baby to Sweat Only on One Side of the Body?
A brief colour change on one side can happen in newborns, and Cleveland Clinic notes it may occur when a baby lies on their side. If one side repeatedly sweats or flushes while the other does not, mention it to your paediatrician so they can check the nerves that control sweating.
Can Teething Cause a Baby to Sweat More?
The AAP says teething, which often starts around 6 months, can cause only a slight rise in body temperature that stays within the normal range. If your baby is sweating and has a temperature above 100.4°F (38°C), teething is unlikely to be the cause, so contact your paediatrician.
