Fever in children and babies: when to go to the ER?

01Understanding what fever is#

Fever is medically defined as an elevation of body temperature above 38°C measured rectally or orally, or above 37.5°C axillary (under the arm). It is essential to understand that fever is not a disease in itself but a symptom that reflects a normal and useful response of the body to an aggression, most often infectious. This fundamental understanding radically changes the way to approach a febrile child.

The mechanism of fever is an active process coordinated by the thermoregulatory centre of the hypothalamus, which raises the internal "thermostat" of the body in response to substances called pyrogens (released either by infectious agents themselves, or by immune cells in response to infection). This thermal elevation has several beneficial effects: it slows the multiplication of bacteria and viruses which do not replicate well at temperatures above their optimum, it stimulates immune system activity (antibody production, white blood cell mobilisation), and accelerates healing. Systematically and drastically fighting fever can paradoxically slow recovery.

An important point to convey to parents: fever in itself is not dangerous up to about 41°C. The temperatures that sick children can reach (39°C, 40°C) are often impressive but do not reflect a vital risk as long as the child remains tonic, hydrated and the cause is identified. The real concern is on the cause of fever, not on the figure itself. A child at 38.5°C with a grey complexion and major apathy is more worrying than a child at 39.5°C who plays and drinks normally.

The reverse is equally true: an absence of fever does not eliminate a serious infection, particularly in newborns whose thermoregulation is immature. This is why in infants under 3 months, we are as attentive to hypothermia as to hyperthermia.

02How to correctly measure temperature#

Measurement precision is essential for appropriate medical decisions. Several routes are possible with different advantages and limits. The following table summarises recommendations.

The rectal route remains the gold standard for medical decisions in infants and young children. Although sometimes poorly accepted by some parents, it is fast (30 seconds), precise and painless if the thermometer is correctly lubricated and inserted 1-2 cm without force. Modern electronic rectal thermometers are comfortable and reliable, around 100-200 MAD.

The buccal route is suitable for children from 5 years able to keep the thermometer under the tongue for 1 to 2 minutes without biting it. Obviously to be avoided immediately after a hot or cold drink. The axillary route is less precise (underestimates real temperature by about 0.5°C) and less reproducible, but has the advantage of simplicity and is useful as second-line.

Tympanic infrared thermometers are fast and well accepted by children, but require correct technique (pull the ear pinna back and up in children to align the canal, aim at the eardrum). Frontal non-contact infrared thermometers, popular since Covid, are very practical for infants and children difficult to measure, but slightly less precise than other methods — to be used as a screening tool to be confirmed if doubtful by a more precise route.

To avoid: mercury thermometers (banned since 2009 due to mercury toxicity) and liquid crystal frontal thermometers (very imprecise, to be abandoned). Smartphone applications claiming to measure temperature have no scientific validity.

03Emergency signs requiring a 141 call#

The distinction between a benign fever manageable at home and a vital emergency is the main issue for parents. Several situations require an immediate call to 141 (SAMU) or paediatric emergency consultation without delay, and it is crucial to know them.

In any infant under 3 months, any fever above or equal to 38°C is an absolute emergency, without exception. The immune system at this age is immature and incapable of effectively localising an infection. Bacteraemia (presence of bacteria in blood), meningitis or pyelonephritis can evolve in a few hours with dramatic consequences. Fever in this age range systematically requires biological workup, lumbar puncture, blood cultures and hospitalisation for probabilistic antibiotic therapy while awaiting results. Never delay consulting such a young febrile infant, even if general state seems correct.

In children over 3 months, several alarming signs justify an immediate call. Fever above 40°C poorly tolerated. Fever persisting beyond 3 days without identified cause. Convulsions occurring during fever — although the majority of febrile convulsions are benign (typical crisis less than 5 minutes in a child of 6 months to 5 years), a first crisis requires medical workup to rule out meningitis or encephalitis, and any prolonged crisis (more than 5 minutes) or repeated requires a 141 call. Abnormal behaviour: unusual and uncontrollable crying (whimpering, plaintive), or conversely extreme apathy, the child who "no longer reacts as usual", who sleeps a lot, who no longer smiles, who does not play — these signs often reflect an underlying severe infection. Rapid or difficult breathing: tachypnoea (high respiratory rate), intercostal retraction (hollowing between ribs on inspiration), nasal flaring, expiratory grunting — signs of pneumonia or severe respiratory distress.

A purpura (red spots that do not fade with glass pressure — vitropression test) is probably the most dramatic sign: it suggests meningococcaemia, an absolute vital emergency where every minute counts. If you see red spots that do not disappear when you press with a transparent glass, it is an absolute vital emergency. Neck stiffness (impossibility to flex neck forward), particularly associated with headache and vomiting, suggests meningitis and requires urgent lumbar puncture.

Repeated vomiting preventing hydration, marked dehydration (dry lips, sunken eyes, persistent skinfold, depressed fontanelle in infants, no urine output for more than 6 hours) are also worrying. Intense persistent headache, morning projectile vomiting, may suggest intracranial hypertension (meningitis, encephalitis, brain abscess). A bulging and tense anterior fontanelle in infants (instead of being flat or slightly depressed) is a sign of intracranial hypertension. Any fragile child (sickle cell disease, immunodeficiency, congenital heart disease, drug immunosuppression, prematurity) with fever should be considered at increased risk and consult quickly.

04Approach according to child's age#

The fever approach varies considerably according to child's age, justifying different conducts.

Infants under 3 months

This is the most vulnerable and demanding age range. Any fever above or equal to 38°C justifies paediatric emergency consultation without delay. Systematic workup generally includes complete clinical examination, complete blood count, CRP and procalcitonin dosing, urinary strip, sometimes blood cultures, and according to context chest X-ray and lumbar puncture for cerebrospinal fluid analysis. Hospitalisation is often necessary for surveillance and probabilistic antibiotic therapy, particularly before 1 month. This approach may seem aggressive but is justified by the potential severity of neonatal infections and the difficulty of clinically diagnosing them at this age.

Children from 3 months to 3 years

Evaluation is more nuanced. Isolated well-tolerated fever, in a child who drinks, plays and keeps normal behaviour, can be monitored at home for 24 to 48 hours with symptomatic treatment (paracetamol, hydration). In presence of warning signs (significant irritability, food refusal, vomiting, marked ENT signs, important cough), medical consultation within 24 hours is recommended. The presence of a warning signal among those mentioned above justifies urgent consultation.

Children over 3 years

The approach is more reassuring as expression and symptom localisation capacities are better. Isolated well-tolerated fever can be monitored at home for several days. Consultation is indicated if fever persists more than 3 days, if general state deteriorates, or if warning signs appear.

05The most common causes#

The aetiology of fever in children follows a relatively constant distribution, largely dominated by benign viral infections.

Benign viral infections constitute the overwhelming majority of childhood fevers. Viral rhinopharyngitis ("cold") causes moderate fever, runny nose, mild cough, sore throat. Flu gives flu-like syndromes with sudden high fever, body aches, intense fatigue. Viral gastroenteritis combines moderate fever, vomiting and diarrhoea. Chickenpox manifests as moderate fever and characteristic vesicular eruption. Roseola infantum (exanthem subitum), frequent in infants, gives a high fever for 3-4 days then an eruption when fever drops — classic cause of isolated fever in babies.

Bacterial infections are more worrying but remain minority. Group A streptococcal pharyngitis in children aged 3-15, to be confirmed by RDT. Acute purulent otitis media, generally associated with viral rhinopharyngitis that has complicated. Community-acquired pneumonia by pneumococcus or Mycoplasma, manifesting as fever, cough, tachypnoea, sometimes chest pain. Pyelonephritis (upper urinary tract infection), particularly in infants and young children, where fever can be isolated without obvious urinary symptom — hence the systematisation of urinary strip in febrile infants. More rarely and more severely, bacterial meningitis, osteomyelitis, septic arthritis, septic shock of various origins.

Vaccine reactions within 24 to 48 hours after vaccination are frequent and benign, generally moderate (38°C-38.5°C), spontaneously resolving, justifying only symptomatic treatment.

Other rarer causes deserve to be considered in certain contexts: Kawasaki disease (vasculitis of coronary vessels) which manifests as prolonged fever more than 5 days associated with at least 4 clinical criteria (conjunctivitis, oral changes, eruption, extremity involvement, cervical adenopathy) — crucial diagnosis as specific early treatment is essential. Hereditary autoinflammatory syndromes (FMF, PFAPA) give periodic recurrent fevers. Medications can cause drug fevers (rare in children). Heatstroke by exposure to excessive heat is a vital emergency.

06Home fever management#

Home management of well-tolerated fever in a child without warning signs combines non-medication measures and antipyretics used judiciously.

Physical measures are simple and effective. Uncover the child: no thick blankets, no jumper, no hat — dress lightly to facilitate heat dissipation. The bedroom temperature should be maintained between 19 and 21°C, neither too hot nor too cold. Lukewarm baths (at 1°C below body temperature, never cold — which would cause paradoxical vasoconstriction) have limited efficacy and may be unpleasant for children; they are not systematically recommended. Abundant hydration is essential: water, milk, herbal teas, soups, diluted juices, to be offered frequently and in small quantities. Rest is important — let the child sleep as much as needed.

Antipyretic medications are useful for child comfort but should not be used systematically at the slightest temperature elevation. Paracetamol is the first-line antipyretic in all children. Dosage: 15 mg per kg every 6 hours, not exceeding 60 mg/kg/day. Available as syrup (most used in children), suppositories, effervescent tablets. Practical doses for usual paediatric syrup at 120 mg/5 mL are as follows.

Ibuprofen can be used in children over 3 months weighing at least 7 kg, at the dose of 10 mg per kg every 8 hours, not exceeding 30 mg/kg/day. It is slightly more powerful than paracetamol on fever and has a complementary anti-inflammatory effect. However, it must be avoided in several situations: chickenpox (risk of severe skin superinfections like necrotising fasciitis), dehydration, digestive disorders with vomiting, taking other anti-inflammatories, coagulation disorders. In case of doubt, ask the pharmacist or doctor.

Aspirin is formally contraindicated in children under 18 in case of viral infection (flu, varicella in particular), due to the risk of Reye syndrome, a rare but potentially fatal complication (acute encephalopathy and liver failure).

Paracetamol-ibuprofen alternation is a sometimes recommended practice but should not be systematic. HAS and British NICE recommendations privilege a single antipyretic as first-line. Alternation may be proposed by the doctor in specific situations (very high fever not yielding to a single product) but increases the risk of dose errors, particularly if several adults administer medications. The prudent rule: a single antipyretic at a time, strictly respecting intervals between intakes, and noting in writing each intake to avoid duplications.

07Antibiotics: not systematic for fever#

An essential point to be understood by parents concerns the place of antibiotics in fever management. As 70 to 80% of paediatric fevers are of viral origin, antibiotics are useless and ineffective in the vast majority of cases — they have no action on viruses. Their systematic prescription "just in case" is bad practice contributing to antibiotic resistance, a major public health problem in Morocco and worldwide.

Antibiotics are indicated only in certain specific situations: streptococcal pharyngitis confirmed by positive RDT, acute purulent otitis media with severity criteria, bacterial pneumonia clinically and radiologically documented, pyelonephritis confirmed by urine culture, bacterial skin infections (extensive impetigo, erysipelas, abscess), bacterial meningitis, septicaemia. In these situations, antibiotics are not only useful but vital.

Conversely, viral infections (rhinopharyngitis, flu, viral gastroenteritis, varicella, roseola, varied viral exanthems) get no benefit from antibiotic treatment and may even suffer from it (digestive side effects, allergies, microbiota disruption, selection of resistant bacteria). If your doctor does not prescribe antibiotics for viral fever, it is because they practise modern and responsible medicine. Conversely, never demand antibiotics "to be sure" — instead demand a precise diagnosis that will allow adapting treatment.

In Morocco, several initiatives raise awareness on this issue: Ministry of Health campaigns for proper antibiotic use, continuing medical education, generalisation of rapid diagnostic tests (strep RDT in health centres). As a parent, you can contribute to this approach by accepting that fever does not systematically require antibiotics, by avoiding self-medication with antibiotics from leftover prescriptions (very dangerous practice), and by privileging a precise medical diagnosis before any treatment.