Fever in babies: what to do and when to seek help
Important notice. This guide is for information only. In babies under 3 months with a temperature ≥38 °C, you must always contact a paediatrician or go to A&E — you should not treat the fever on your own at that age. If you have any doubt about dose, frequency or combining antipyretics in your child, the final decision rests with your paediatrician or pharmacist based on your child's current weight.
Fever in a baby is not an illness in itself — it is a response of the immune system to an infection or another cause. This is a pharmacist's guide to what really helps (physical measures, hydration, assessing warning signs) and what you need to know before giving any antipyretic such as paracetamol (Apiretal, Gelocatil Pediátrico) or ibuprofen (Dalsy).
Quick summary:
- True fever: axillary temperature ≥ 38 °C (37.5–38 °C is low-grade fever).
- Under 3 months: temperature ≥ 38 °C → always paediatrician or A&E.
- Before using medicine: light clothing, frequent fluids, cool environment.
- Antipyretics: dose always by weight and paediatric plan — never by rough age bands.
From what temperature is it true fever in a baby?
This matters because it guides when you act and when you can safely wait. The usual paediatric criterion, with an axillary thermometer, is:
- Normal temperature: up to 37.4 °C.
- Low-grade fever: 37.5–37.9 °C. Monitor without medication.
- Fever: ≥ 38 °C. It is considered fever and you assess what measures are needed.
- High fever: ≥ 39 °C. Often comes with more discomfort and needs more active attention.
With a rectal thermometer the reading is around 0.3–0.5 °C higher than axillary. With ear or forehead infrared thermometers, the reliability range depends on the model and how you use it.
Fever is not the enemy — it is a defensive response
It is very common to feel the urge to bring a baby's temperature down as quickly as possible, but fever has a biological role: raising body temperature slows the replication of many viruses and bacteria and activates the immune response. The aim of treatment is not to «normalise the temperature» but to improve your child's comfort.
- A baby with 38.5 °C who is calm, feeding and playing may not need an antipyretic at that moment.
- A baby with 38 °C who is very listless, irritable or not resting does benefit from an antipyretic.
- The thermometer guides you, but the overall picture rules. How your child looks and behaves matters more than the number.
Physical measures before using medicine
Most current paediatric guidelines recommend starting with physical measures when the fever is tolerated and your baby does not have red-flag symptoms:
- Light clothing: remove blankets, jumpers and extra layers. Over-wrapping can make the temperature rise further.
- Cool environment: room around 20–22 °C, without direct draughts.
- Frequent fluids: offer breastfeeds, bottle feeds or water (depending on age) more often. Fever increases fluid loss.
- Lukewarm bath (water at 34–36 °C) for 10–15 minutes: can help your child feel more comfortable. Never use cold water or alcohol rubs (both are contraindicated in children).
- Lukewarm compresses on forehead, neck and wrists if your child accepts them.
When is medicine recommended and which antipyretic?
You consider an antipyretic when fever clearly affects your child's wellbeing: irritability, pain, difficulty sleeping or marked discomfort. There are two main options in children, always following medical advice:
- Paracetamol (Apiretal, Gelocatil Pediátrico): first choice in most situations. It can be used from the first months of life with a paediatric plan. Its safety profile is well established when dosed correctly.
- Ibuprofen (Dalsy, Ibudol Pediátrico): from 3 months onwards. It adds an anti-inflammatory effect when there is also sore throat or ear pain. Your child needs to be well hydrated while taking it.
- Dose: calculated by weight (kg), not by age. Your paediatrician or pharmacist will give you the exact schedule for your child. Never copy the dose from a sibling or from an old leaflet version.
- Alternating paracetamol and ibuprofen: this is not the first option. It may be considered in specific cases only under paediatric supervision, respecting intervals and without shortening dosing times.
- Nev er give aspirin (acetylsalicylic acid) under 16 years because of the risk of Reye's syndrome.
Having the correct bottle and the original dosing syringe from that brand helps avoid mistakes: the same active ingredient can come in different strengths (for example 100 mg/ml vs 40 mg/ml), and confusing them completely changes the dose given.
Warning signs that need medical assessment
The following situations mean you should not wait at home — contact your paediatrician or go to A&E:
- Younger than 3 months with temperature ≥ 38 °C. This is an absolute rule.
- Fever lasting more than 48–72 hours without an obvious cause or not responding to correctly dosed antipyretics.
- Fever together with: skin spots that do not fade when pressed, stiff neck, marked lethargy, persistent vomiting, breathing difficulty, continuous moaning or inconsolable crying.
- Febrile seizure (rhythmic movements with loss of consciousness). This always needs medical assessment even though it is often benign.
- Fever in a child with an underlying condition (heart disease, immune deficiency, cancer) — they follow specific medical protocols.
- Signs of dehydration: dry mouth, crying without tears, dry nappy for more than 6–8 hours, sunken eyes or sunken fontanelle (soft spot).
Thermometers: which type to choose for your child's age
The thermometer is your basic tool for checking fever in babies. Each type has its place and its margin of error:
- Digital axillary thermometer: most recommended in paediatrics for reliability. Suitable for all ages. Inexpensive and easy to use.
- Digital rectal thermometer: most accurate for babies under 3 months, although it needs correct technique and a bit of practice.
- Eardrum infrared thermometer: quick and comfortable but less accurate under 6 months (ear canal still narrow).
- No-contact forehead infrared thermometer: very practical so you do not wake your baby up, although readings can vary quite a lot depending on technique and room conditions.
I usually recommend having a digital axillary thermometer at home as your reference device and a forehead infrared thermometer as support for quick checks if you wish.
Babies under 3 months: a special case
In very young babies any fever needs different handling and should never be managed independently at home:
- Temperature ≥ 38 °C rectal → medical review or A&E without delay. With an immature immune system this may signal a serious infection that needs proper assessment (blood tests, cultures).
- Do not give antipyretics on your own initiative before medical assessment in this age group.
- Do not «wait to see if it goes down» or try to lower it with aggressive physical measures.
- Write down temperature readings, time taken and associated symptoms so you can give precise information to the paediatrician.
For older babies and children, watching how your child looks overall, using simple physical measures and giving an antipyretic when their comfort really requires it will resolve most common febrile episodes within 2–3 days.
Thermometers: which to choose according to your baby’s age
| Type | Age range | Reliability | Practical note |
|---|---|---|---|
| Digital axillary | All ages | High (reference) | The most recommended in paediatrics; cheap and easy |
| Digital rectal | Under 3 months | Maximum | Accurate but requires proper technique |
| Infrared ear | ≥ 6 months | Medium | Fast; less accurate <6 m due to narrow ear canal |
| Contactless forehead | All ages | Variable | Does not wake the baby; sensitive to technique and environment |
Frequently asked questions
Scientific references
