When to get help

Ask for urgent advice — NHS 111 in the UK, your GP out-of-hours service in Ireland, your paediatrician in the US or Canada, healthdirect on 1800 022 222 in Australia, Healthline on 0800 611 116 in New Zealand — if your baby is under three months and has a temperature of 38°C (100.4°F) or higher, is three to six months with 39°C (102.2°F) or higher, has a fever lasting five days or more, is feeding much less than usual, or is showing signs of dehydration.

Get help urgently too if the skin around any spot becomes hot, red, swollen or painful, or starts oozing. Chickenpox breaks the skin barrier, and broken skin can become bacterially infected — impetigo is a common example, and it is treatable but needs treating.

Call emergency services — 999, 112, 911, 000 or 111 depending on your country — for the general baby red flags: a rash that does not fade under a pressed glass, difficulty breathing, blue, grey or mottled skin, a first seizure, or a baby who is floppy or cannot be roused.

See a GP non-urgently if you are not sure it is chickenpox, or if you are breastfeeding and have symptoms yourself.

The three stages

The main symptom is an itchy, spotty rash that can appear anywhere on the body. Before or after the rash, your baby may have a high temperature, aches and pains, and loss of appetite. The NHS describes three stages, and notes that new spots can appear while others are already blistering or scabbing — so all three can be present at once.

Stage 1: small spots. Anywhere on the body, including inside the mouth and around the genitals, which can be painful. They may be red, pink, darker than surrounding skin or the same colour, and are harder to see on brown and black skin.
Stage 2: blisters. The spots fill with fluid. These are very itchy and may burst.
Stage 3: scabs. Some scabs are flaky, others leak fluid.

The CDC adds scale: a person with chickenpox may have as many as 500 blisters, illness usually lasts about four to seven days, and it usually takes about a week for all the blisters to become scabs.

The ibuprofen warning

This is the single most important thing on this page after the red flags. The NHS says: do not use ibuprofen unless you are told to by a doctor, as it may cause serious skin infections. Its general fever advice repeats the point — do not give ibuprofen to a child who has chickenpox.

Paracetamol is the usual choice instead, and the NHS lists it under what to do for chickenpox. Suitability depends on your baby's age and weight, so read the packaging or ask a pharmacist. Aspirin is not for children under 16 in any circumstances.

Easing it at home

Drink plenty of fluids. For a baby that means normal feeds, offered more often.
Cut fingernails short and put socks on their hands at night to stop scratching.
Cooling creams or gels from a pharmacy can help.
Ask a pharmacist about antihistamine medicine for itching, and whether it suits your baby's age.
Bathe in cool water and pat — do not rub — the skin dry.
Dress in loose clothes.

Scratching causes scarring, which is why the nails and socks advice sits so high on the NHS list. It is also the main route to a secondary skin infection.

Who your baby must stay away from

The NHS is emphatic: do not go near newborn babies, anyone who is pregnant, or anyone with a weakened immune system, because chickenpox can be dangerous for them. The CDC says chickenpox can be serious and even life-threatening during pregnancy, in babies, in adolescents and adults, and in people with weakened immune systems.

This is more restrictive than most childhood illnesses, and it is worth planning around: no visits, no shared waiting rooms if avoidable, and a phone call before any appointment.

How contagious, and for how long

Very. The CDC says up to 90% of people who are not immune and are close to someone with chickenpox will catch it, and that a person is contagious from one to two days before the rash begins until all lesions have crusted over. The incubation period is about two weeks, usually 10 to 21 days after exposure.

For nursery and childcare, the NHS rule is to stay off until all the spots have formed a scab, which is usually five days after the spots first appeared. UKHSA guidance for education and childcare settings uses the same crusting-over principle.

Vaccination differs by country

This is where advice diverges sharply, and there is no single right answer to quote. The CDC says the best way to prevent chickenpox is the chickenpox vaccine, which is part of the routine childhood schedule in the United States. In the UK, chickenpox vaccination has historically not been part of the routine schedule in the same way. Check what your own country's programme offers rather than assuming, and if your baby has a weakened immune system, ask specifically.

Shingles, and why it matters here

After chickenpox, the varicella-zoster virus stays dormant in the body and can reactivate later in life as shingles. The CDC notes the reverse route too: someone who has never had chickenpox or the vaccine can catch the virus from a person with shingles, through direct contact with the fluid from shingles blisters or by breathing in virus particles from them. They will develop chickenpox, not shingles. If a grandparent has shingles, that is a real exposure route for a baby.

Chickenpox in Babies