Fever
Elevated body temperature (≥38°C) indicating the body's immune response to infection or illness.
| Normal temperature | 36.4°C–37.5°C (armpit) |
| Fever threshold | ≥38°C |
| High fever | ≥39°C |
| Medical emergency | ≥40°C or under 3 months with any fever |
Age-Specific Protocols
Treatment approach varies dramatically by infant age due to infection risk and diagnostic difficulty:
| Age | Fever Response | Intervention Level |
|---|---|---|
| 0–28 days | Any fever ≥38°C | Hospital admission, spinal tap, IV antibiotics |
| 1–3 months | Fever ≥38°C | Medical assessment within hours, possible spinal tap |
| 3+ months | Fever with illness signs | GP assessment, home management if well-appearing |
| 6+ months | Uncomplicated fever | Home management, paracetamol/ibuprofen as needed |
Why the difference? newborns have 3–20% risk of bacterial infection (including meningitis) with fever, and clinical signs are harder to detect. Post-vaccination (8+ weeks), bacterial infection risk drops significantly.
Measuring Temperature
Method: Digital thermometer in armpit (axillary)
- Place thermometer in armpit centre
- Hold arm against body for duration specified (typically 1–2 minutes)
- Wait 5 minutes after bath/feeding for accurate reading
- Add 0.5°C to armpit reading for core temperature estimate (optional)
Forehead strips and ear thermometers: Less reliable in infants under 6 months.
Home Management (3+ Months)
Immediate actions:
- Maintain hydration (continue breastfeeding/formula on demand)
- Light clothing (one layer, room temperature 18–20°C)
- Monitor every 2–4 hours, including overnight
- Paracetamol (from 2 months, 15mg/kg every 4–6 hours, max 4 doses/24h)
- Ibuprofen (from 3 months, 10mg/kg every 6–8 hours with food)
Do not:
- Undress completely or sponge with cool water (causes shivering, raises core temperature)
- Alternate paracetamol and ibuprofen without medical advice
- Give aspirin (risk of Reye's syndrome)
Warning Signs
Seek immediate medical attention if:
- Under 3 months with any fever
- Fever ≥40°C at any age
- Fever lasting >5 days
- non-blanching rash (does not fade under glass pressure)
- Seizure (febrile convulsion)
- Difficulty breathing or grunting
- Unusually drowsy, floppy, or unresponsive
- Refusing all feeds for 8+ hours
- Dry nappies for 8+ hours (dehydration)
- Persistent vomiting
- Severe headache or stiff neck
Febrile Seizures
Occur in 3–5% of children aged 6 months–5 years during rapid temperature rise.
During seizure:
- Place child on side on soft surface
- Do not restrain or put anything in mouth
- Time the seizure duration
- Call 999 if seizure lasts >5 minutes or child is under 6 months
After seizure: Child typically drowsy for 30–60 minutes. GP assessment required same day.
Duration & Recovery
Typical viral fever: 1–4 days (NHS guidance)
Post-fever monitoring: Temperature fluctuations normal for 24 hours after fever breaks
Return to childcare: 24 hours after fever resolves without medication
Common Causes by Age
| Age | Most Likely Causes |
|---|---|
| 0–3 months | Viral infection (70–80%), UTI, bacterial infection (3–20%) |
| 3–12 months | Viral URTI, post-vaccination reaction, roseola, ear infection |
| 1–3 years | Viral infections, tonsillitis, hand-foot-mouth disease |
Post-vaccination fever: Common 6–24 hours after vaccines, typically mild (38–38.5°C), resolves within 48 hours.
When Fever Is Protective
Fever enhances immune response by:
- Inhibiting bacterial/viral replication
- Increasing white blood cell production
- Improving antibody effectiveness
Treatment goal: Comfort, not elimination. Mild fever (38–38.5°C) in well-appearing child may not require medication.
See also: Thermometers, Paracetamol Dosing, Febrile Seizures, Dehydration, Meningitis Signs, When to Call 999