Child Fever — Causes, When to Worry & Parent's Guide to Treatment — Symptoms, Causes & Treatment | MyMedicPlus

Fever in children is defined as a core body temperature above 38 degrees Celsius (100.4 degrees Fahrenheit). It is a normal immune response to infection — elevated temperature impairs pathogen replication and enhances immune function. Most childhood fevers are caused by self-limiting viral infections (common cold, influenza, COVID-19, roseola, gastroenteritis) and resolve within 3-5 days without specific treatment. However, fever in children under 3 months or with certain warning signs (high fever, rash, stiff neck, altered consciousness) requires urgent medical assessment to exclude serious bacterial infections such as meningitis, septicaemia, pneumonia, or urinary tract infection. The parental experience of a febrile child causes significant distress, and 'fever phobia' — exaggerated fear of fever and its consequences — drives overuse of emergency services and unnecessary antibiotic prescriptions. Healthcare professional education to help parents use the NICE traffic light system empowers confident home assessment of well-appearing febrile children and appropriate safety-netting. Viral fevers in well-appearing children who maintain hydration and are alert between fever spikes can safely be managed at home with antipyretics and close monitoring.

Most common causes of fever in children: upper respiratory tract infections (URTI — cold, pharyngitis, otitis media); influenza and other respiratory viruses; COVID-19; gastroenteritis (from rotavirus, norovirus, Salmonella); urinary tract infection (UTI — suspect in infants and young girls); roseola infantum (HHV-6 — fever followed by rash in children aged 6 months to 2 years); measles, chickenpox, and other childhood viral illnesses. Bacterial causes requiring antibiotic treatment: bacterial meningitis (Neisseria meningitidis, Streptococcus pneumoniae), pneumonia, otitis media, skin and soft tissue infections, urinary tract infection, and epiglottitis. Risk factors for serious infection: age under 3 months, fever above 39 degrees Celsius, unvaccinated status, immunocompromised state, and certain ethnic backgrounds.

Fever itself: temperature above 38 degrees Celsius (axillary), above 38.5 degrees Celsius (tympanic/rectal), with hot skin, flushed appearance, rigors (shivering), sweating. Associated symptoms vary by cause: runny nose, sore throat, cough (URTI); ear pain (otitis media); rash (viral exanthem, chickenpox, roseola, measles); vomiting and diarrhoea (gastroenteritis); dysuria or offensive urine (UTI); and stiff neck, photophobia, purpuric non-blanching rash, and altered consciousness (meningococcal disease — MEDICAL EMERGENCY). NICE traffic light system: GREEN (well between fever peaks, normal colour, moist, normal cry, no risk factors — likely viral); AMBER (moderate risk); RED (high risk — requires immediate assessment). Kawasaki disease — a systemic vasculitis causing fever lasting more than 5 days with at least 4 of 5 features (rash, conjunctival injection, mucositis/cracked red lips, lymphadenopathy, extremity changes including oedema and periungual peeling) — is an important diagnosis not to miss in toddlers, as untreated disease causes coronary artery aneurysms in 25% of children.

Temperature measurement: rectal thermometer (most accurate in children under 4 weeks); tympanic (ear) thermometer (convenient for older infants/children); axillary (armpit) temperature is least accurate but widely used. Clinical assessment: NICE traffic light system assesses colour, activity, respiratory signs, circulation/hydration, and other features to stratify risk. Investigations if bacterial infection suspected: urine dipstick and culture (all febrile children under 5 without obvious source); FBC, CRP, PCT (procalcitonin); blood culture; chest X-ray if respiratory signs; lumbar puncture (CSF) if meningitis suspected; throat swab (if group A Streptococcus — streptococcal pharyngitis — suspected). Viral testing (COVID-19, influenza, RSV) as appropriate. Procalcitonin (PCT) above 0.5 ng/mL has better specificity than CRP for serious bacterial infection in febrile children, with a negative predictive value of 98% for bacteraemia. PCT-guided management reduces antibiotic use in febrile children without increasing adverse outcomes.

Fever management: the primary goal is to relieve the child's discomfort, not necessarily to reduce temperature to 'normal'. Antipyretics: paracetamol (acetaminophen) 15 mg/kg every 4-6 hours (maximum 4 doses per 24 hours) — suitable from 2 months of age; ibuprofen 5-10 mg/kg every 6-8 hours (suitable from 3 months of age, avoid in dehydration/vomiting or if chickenpox). Do NOT alternate paracetamol and ibuprofen routinely (it increases medication errors and evidence for benefit over single agent is weak). Do NOT give aspirin to children under 16 years (risk of Reye's syndrome). Hydration: encourage regular oral fluids (water, diluted squash, breast milk, formula). Tepid sponging is not recommended. Antibiotics if bacterial infection is confirmed. Referral to hospital for high-risk features (RED or AMBER with concerns).

Most viral fevers in children are self-limiting without complications. However, missing serious bacterial infection is the main risk of inadequate assessment: bacterial meningitis (especially meningococcal disease) can be rapidly fatal — 10% mortality even with treatment; survivors may have limb amputation, deafness, or brain damage; the non-blanching purpuric rash and meningococcal septicaemia can progress from mild fever to circulatory collapse within hours. Febrile seizures (convulsions triggered by rapid temperature rise) occur in 2-4% of children aged 6 months to 5 years — frightening for parents but usually benign and brief (under 5 minutes); prolonged febrile seizures (over 15 minutes) require emergency management and investigation.

Keep children's vaccinations up to date — the UK national immunisation schedule protects against meningococcal B and C, Hib, pneumococcal, measles, MMR, chickenpox (varicella), flu, COVID-19, and many other causes of childhood fever. Annual influenza vaccination for all children aged 2-17 (nasal flu spray). Practice good hand hygiene — wash hands before meals and after the toilet; teach children to cough and sneeze into tissues. Avoid taking ill children to nursery or school during the first 24-48 hours of fever (infectious period). Know the 'Glass Test' — press a glass against a non-blanching rash; if it does not fade under pressure, seek immediate emergency care (possible meningococcal disease). Trust parental instinct — if a parent feels something is seriously wrong, seek medical assessment even if the child appears to improve temporarily.

Call 999 immediately or take child to emergency department for: non-blanching rash (press a glass on the skin — if the rash does not fade, it may indicate meningococcal disease — a life-threatening emergency); difficulty breathing, working hard to breathe, or breathing very fast; blue lips or skin; severe drowsiness — difficult to wake, not responding to stimulation; a high-pitched, unusual cry in infants; a bulging fontanelle (soft spot on head) in infants; repeated seizures or a first febrile convulsion lasting more than 5 minutes. Contact a GP or 111 same day for: fever in a baby below 3 months (above 38°C); fever in a baby 3-6 months (above 39°C); fever persisting beyond 5 days; child appears very unwell to a parent who knows the child well; rash present with fever; or failure to drink any fluids for more than 8 hours. Trust your instincts — if you are seriously worried about your child, seek medical help without delay.