Read this part first

Blue or grey lips, tongue or face in a baby is an emergency. The American Academy of Pediatrics puts it plainly: "persistently blue skin coloring is a sign the heart or lungs are not operating properly, and the baby is not getting enough oxygen in the blood. Immediate medical attention is essential."

NICE says the same thing from the other direction, in three separate guidelines. In its fever guideline NG143, a child with pale, mottled, ashen or blue skin, lips or tongue is placed in the high-risk group for serious illness — the red category of the traffic light system. In its postnatal care guideline NG194, "appearing pale, ashen, mottled or blue (cyanosis)" is one of the named red flags for serious illness in young babies, and NICE's instruction when a red flag is present is immediate assessment, with 999 if the baby's condition is immediately life-threatening.

And in NG254, NICE's sepsis guideline for under-16s, the skin row of the risk table for children under five puts "mottled or ashen appearance", "cyanosis of skin, lips or tongue" and "non-blanching petechial or purpuric rash" together in the high risk column, with "pallor of skin, lips or tongue" in the moderate to high risk column. Three separate NICE guidelines converging on the same short list is about as strong a signal as this kind of guidance gets.

Call your local emergency number — 999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, 111 in New Zealand — if the blue is on the lips, tongue, gums or face, or if it will not go away.

The kind that is usually nothing

Now the common version. The AAP's list of common newborn conditions includes an entry titled "blue baby", and it says: "Babies may have mildly blue or purple hands and feet, which is usually normal. If their hands and feet turn slightly blue from cold, they should return to pink as soon as they are warm."

Clinicians call this acrocyanosis — blueness of the extremities. It is extremely common in the first days and weeks, and it is a circulation quirk rather than an oxygen problem: a newborn's smallest blood vessels narrow readily in response to cold, so the hands and feet lose colour first while the trunk stays pink.

The AAP adds one more normal case: "Occasionally the face, tongue, and lips may turn a little blue when the newborn is crying hard, but once she is calm, her color should quickly return to normal." The key words are once she is calm. A hard cry that briefly changes colour and resolves the moment it stops is different from colour that persists.

Mottled and blotchy skin

The other pattern parents photograph is marbling: a lacy, blotchy, purple-pink pattern across the trunk and limbs. The AAP describes it in its account of how newborns look: "Mottled or blotchy-looking patches are commonly caused by exposure to cool air and will disappear quickly if you cover her again."

That word quickly is doing the work. Mottling that appears when a nappy is off in a cool room and vanishes once your baby is dressed is temperature. Mottling that is there in a warm, dressed, settled baby is on NICE's red list and is a reason to be seen straight away.

How to tell them apart at home

Look centrally, not peripherally. Lips, tongue and the inside of the mouth are what matter. Hands and feet are the least reliable place to judge a baby's oxygen.
Warm them and look again. Skin-to-skin contact, a blanket over the top, or simply dressing them. Cold-related colour changes reverse within minutes.
Check the whole picture. Feeding, alertness, breathing effort and temperature tell you more than colour alone. NICE warns that individual signs are of limited value in young babies, which is exactly why the red flag lists are lists.
Do not rely on a consumer pulse oximeter or sock monitor. These are not validated screening tools for home use, and NICE notes that even clinical pulse oximeters can overestimate or underestimate saturation, with overestimation reported in people with dark skin.

Assessing colour on darker skin

Cyanosis is harder to see on brown and black skin, and this is a known cause of delay. Check the lips, the tongue, the gums, the inside of the eyelids and the palms and soles, where colour change shows up more reliably than on the face. NICE's guidance is written around pallor, mottling and cyanosis without qualification, and reported parental concern is explicitly to be taken seriously by professionals — so if the colour looks wrong to you, say so, and say where you are seeing it.

Keeping a newborn warm without overheating

Cold hands prompt parents to pile on layers, and that has its own risk. The HSE's guidance on baby sleep temperature is that a room of about 16C to 20C is a comfortable range, and that you should check whether a baby is too hot by feeling the chest or the back of the neck rather than the hands and feet, which are normally cooler. Signs of overheating include sweating, damp hair and a hot chest. A baby who is warm centrally with cool hands is dressed correctly, not underdressed.

When to call

Call your local emergency number (999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, 111 in New Zealand) if your baby:

Has blue or grey lips, tongue, gums or face, or blueness that does not go when they are warm and calm.
Looks pale, ashen or mottled while warm and settled.
Is grunting with each breath, breathing over 60 breaths a minute, flaring their nostrils or drawing their chest in under the ribs.
Is unresponsive or unrousable, or has a weak, abnormally high-pitched or continuous cry.
Has a temperature of 38C (100.4F) or above, or below 36C (96.8F).
Has a bulging fontanelle, neck stiffness, a seizure, or a rash that does not fade under a pressed glass.

That is NICE's red flag list for serious illness in young babies, from NG194, and every skin item on it also appears in the high risk column of NICE's sepsis guideline NG254.

Speak to your midwife, health visitor, public health nurse or GP if: the blueness of the hands and feet is not settling over the first weeks, your baby goes dusky during feeds, they tire or sweat while feeding, or they are not gaining weight. Colour change during feeding is a specific thing worth naming, because feeding is a newborn's main exertion.

What to let go of

Cold hands and feet in a newborn are not evidence that your baby is cold, that the room is too cold, or that they need another layer. The reliable check is the chest. And no amount of blueness in the hands, on its own, in a warm, feeding, alert baby, means anything about the heart or lungs — which is precisely why the guidance keeps pointing you back to the lips.

Newborn Blue Hands and Mottled Skin