Fever in Babies & Toddlers
Content reviewed against published AAP, AAP, CDC guidelines
Last reviewed:
Fever is defined as a rectal temperature of 100.4°F (38°C) or higher. It is the body's natural response to infection and is not itself an illness. In young babies under 3 months, any fever requires immediate medical evaluation.
Key takeaways
- Fever is defined as a rectal temperature of 100.
- Most common cause: Viral infection (cold, flu, roseola)
- Emergency: Baby under 3 months with ANY fever (rectal temp 100.4°F / 38°C or higher)
- Home care: Dress baby in light clothing — do not bundle up
Possible Causes
When to Seek Help
Emergency — Call 911 or go to ER:
- Baby under 3 months with ANY fever (rectal temp 100.4°F / 38°C or higher)
- Fever with purple/red spots that don't blanch (petechiae)
- Fever with stiff neck, bulging fontanelle, or severe headache
- Fever with difficulty breathing
- Fever with seizure lasting more than 5 minutes
- Baby is unresponsive or extremely difficult to wake
Urgent — See doctor today:
- Baby 3-6 months with fever above 102°F (38.9°C)
- Fever with signs of dehydration (no wet diapers 6+ hours)
- Febrile seizure (even if brief — first episode needs evaluation)
- Fever above 104°F (40°C) at any age
- Fever persisting more than 5 days
Same-day appointment:
- Fever 100.4-102°F in baby 3-6 months who otherwise seems well
- Fever lasting more than 3 days with no clear source
- Fever returning after being gone for 24+ hours
- Baby not drinking well but still making some wet diapers
Monitor at home:
- Low-grade fever (under 102°F) with mild cold symptoms in baby over 6 months
- Fever after vaccination (common, usually resolves in 24-48 hours)
- Baby over 6 months with fever who is still drinking, playing, and making wet diapers
By Age
0-3 months
Normal: Normal temperature ranges from 97.7-99.5°F rectally. Slight variations after feeding or bundling are normal.
Worry if: ANY rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months requires IMMEDIATE medical evaluation — call your pediatrician or go to the ER right away, even if baby seems fine.
3-6 months
Normal: Low-grade fevers with mild colds are common and often resolve in 1-2 days.
Worry if: Fever above 102°F (38.9°C), fever lasting more than 24 hours, or baby appearing ill (not feeding, very sleepy, irritable).
6-12 months
Normal: Fevers with viral illnesses are common as maternal antibodies wane. Many babies get multiple febrile illnesses as immunity develops.
Worry if: Fever above 104°F (40°C), fever lasting more than 3 days, or fever with rash, stiff neck, or persistent vomiting.
1-3 years
Normal: Frequent fevers with daycare illnesses are normal. Height of fever does not necessarily indicate severity of illness.
Worry if: Fever lasting more than 5 days, fever with difficulty breathing, signs of dehydration, or child appears very unwell.
Home Care
- Dress baby in light clothing — do not bundle up
- Offer frequent breast/bottle feeds to prevent dehydration
- Acetaminophen (Tylenol) for babies 2+ months per doctor guidance
- Ibuprofen (Motrin/Advil) for babies 6+ months
- Lukewarm (not cold) sponge bath if baby is uncomfortable
- Keep room at comfortable temperature
- Do NOT give aspirin to children
- Monitor wet diapers — aim for at least 4-6 per day
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Sources
All content follows our editorial policy and is reviewed against published clinical guidelines.
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Related Symptoms
Bottom line
Most cases of fever in babies are not emergencies. However, seek immediate care if baby under 3 months with any fever (rectal temp 100.4°f / 38°c or higher).
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.