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Baby Fever and Common Illnesses: What Parents Should Know

How to check temperature, comfort a sick baby and recognise red flags.

Before you use this guide: This is general educational information, not an individual medical assessment. We do not identify a clinician reviewer on this page, so please confirm personal health decisions with your doctor, midwife or paediatrician.

Babies get coughs, colds and fevers often in their first year, especially once they have contact with other children. Most illnesses are mild and pass without treatment, but young babies can become unwell quickly. Knowing what is normal, how to check your baby and when to get help will make these times less stressful.

Taking a temperature

• Use a digital thermometer and follow its instructions. Under the arm is the usual place for a newborn. Some ear and forehead thermometers are suitable for older babies, so check the age range on the box.
• Do not use glass mercury thermometers, and do not rely on fever strips or on touching the forehead.
• A temperature of 38 °C (100.4 °F) or higher is generally considered a fever.
• A fever is a sign that the body is fighting an infection. How your baby looks and behaves matters more than the number.

Seek urgent medical help if

• Your baby is under three months old and has a fever of 38 °C (100.4 °F) or higher. Call your doctor, or go to an emergency department, the same day.
• Your baby is three to six months old with a temperature of 39 °C (102.2 °F) or higher
• Your baby is struggling to breathe, is breathing very fast, grunting, or the skin pulls in under the ribs or around the neck, or the lips look blue or grey
• Your baby is very drowsy, floppy, hard to wake, or has a weak, high-pitched or unusual cry
• There is a rash that does not fade when you press a glass against it
• Your baby is not feeding, keeps vomiting, vomits green bile, or has had no wet nappy for six to eight hours
• The soft spot on the head looks sunken or bulges, or your baby seems to dislike light or has a stiff neck
• Your baby has a seizure
• A fever has lasted more than five days, or your baby seems to be getting worse

Trust your instincts. If you are worried, call your doctor, nurse line or emergency number, even if your baby does not tick any of these boxes.

Comforting a mildly unwell baby

• Offer frequent feeds, because fluids prevent dehydration. Breastfed babies may want to feed more often.
• Dress your baby in light clothing and keep the room comfortably cool. Do not wrap them up or use cold baths or sponging.
• Hold, cuddle and watch your baby closely. Check on them often, including at night.
• Do not give any medicine to a baby under three months without a doctor's advice. For older babies, paracetamol (acetaminophen) or ibuprofen may help if your baby is uncomfortable, using the dose on the packet for their weight and age. Ibuprofen is not suitable for very young babies. Ask your pharmacist which is right for yours.
• Never give aspirin to a baby or child.
• Do not give cough and cold medicines to babies.

Common childhood illnesses

• Colds: a runny or blocked nose, cough and sometimes a mild fever. Babies often get many colds in their first year. They usually last about a week to ten days. Saline nose drops can help a blocked nose.
• Bronchiolitis: caused by a virus such as RSV, common in winter. It starts like a cold, then causes a cough, fast or noisy breathing and feeding difficulties. Most babies recover at home, but get help if breathing is fast or hard, or your baby takes less than half their usual feeds or has fewer wet nappies.
• Croup: a harsh, barking cough and noisy breathing, often worse at night. Seek urgent help if there is noisy breathing when your baby is resting or distress.
• Ear infections: pulling at an ear, fever, irritability and poor feeding or sleeping. See a doctor.
• Gastroenteritis: vomiting and diarrhoea, with a risk of dehydration. Keep feeding, ask about oral rehydration solution and seek help if your baby is not passing urine or looks unwell.
• Hand, foot and mouth disease: a fever, mouth ulcers and a blistery rash on the hands and feet. It usually clears in a week.
• Roseola and some other viral rashes: a high fever for a few days, followed by a rash as the fever fades. Always check a new rash with a doctor if you are unsure.

Teething can make a baby grizzly and may cause a slightly raised temperature, but it does not cause a high fever. Do not assume a high fever is teething.

Fever after vaccinations

A mild fever and fussiness are common for a day or two after vaccinations. If your baby is very unwell, has a high fever or a fever that does not go away, see a doctor. Read more in our guide to baby check-ups and vaccinations.

If your baby has a seizure

Some babies and young children have a seizure with a fever (febrile seizure), usually between about six months and five years. It is frightening but is usually brief and not harmful. Place your baby on their side on a safe surface, do not put anything in their mouth, and note the time. Call emergency services if it is your baby's first seizure, if it lasts more than five minutes, or if your baby does not wake up or recover normally afterwards.

Preventing the spread of illness

• Wash your hands often and ask visitors to do the same.
• Keep your baby away from people who are unwell where you can.
• Keep vaccinations up to date. Pregnant women are often offered vaccines that pass on protection to the baby.
• Do not smoke in the home or the car.
• Breastfeeding, if you are able to, helps protect against infection.

Where to check current advice

Guidance differs a little between countries, so check the latest advice from your own health service: the NHS in the UK, the HSE in Ireland, the CDC and the American Academy of Pediatrics in the US, the Canadian Paediatric Society in Canada, or the Raising Children Network in Australia.

This content is for general information only and is not medical advice. Every pregnancy and every baby is different. Always talk to your doctor, midwife or paediatrician about your own situation, and seek urgent care if you are worried.