Infant diseases · Educational
Infant Fever: Symptoms, Causes & Warning Signs
Rectal temperature of 38.0°C (100.4°F) or higher in an infant under 3 months is treated as an emergency until a clinician rules out serious infection.
Parental Care Hub helps parents learn about common infant diseases, baby symptoms, newborn care, safe sleep, feeding concerns and when to contact a pediatrician.
Emergency first
Any rectal temperature ≥ 38.0°C (100.4°F) under 3 months, temperature below 36.5°C, difficulty breathing, a baby who will not rouse, or a spreading unusual rash. Go to emergency care now.
What this means
Fever is a rise in body temperature, often from infection. In young infants it can be the only early sign of a serious bacterial illness. A rectal reading is the most reliable method in this age group. This page explains baby symptoms parents watch for — it is not a diagnosis or a medicine-dose tool.
Baby symptoms to notice
- Rectal temperature of 38.0°C (100.4°F) or higher
- Poor feeding or fewer wet diapers
- Unusual sleepiness, irritability, or a mottled look
- In older infants: a warm forehead plus reduced play
Safe home care (not a prescription)
Record the exact temperature and the time. Use light clothing. Do not delay evaluation in an infant under 3 months in order to “try medicine first.” Do not give any fever medicine unless a clinician has already told you the product and dose for that child. Keep the infant comfortable while you travel to care.