Medical Conditions

Herpetic Gingivostomatitis (Mouth Sores) in Babies

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published AAP, AAP, NIH guidelines

Editorial policy

Last reviewed:

If your baby has been diagnosed with or you suspect herpetic gingivostomatitis (mouth sores) in babies, here is what the evidence says.

The short answer

Herpetic gingivostomatitis is a common first-time infection with the herpes simplex virus (HSV-1) that causes painful sores on the gums, tongue, lips, and inside the cheeks. It is most common in children between 6 months and 5 years. While the sores look alarming and can make eating very painful for several days, the infection resolves on its own within 7-14 days. The main concern is keeping your child hydrated while their mouth is sore.

Key takeaways

  • Herpetic gingivostomatitis is a common first-time infection with the herpes simplex virus (HSV-1) that causes painful sores on the gums, tongue, lips, and inside the cheeks. It is most common in children between 6 months and 5 years. While the sores look alarming and can make eating very painful for several days, the infection resolves on its own within 7-14 days. The main concern is keeping your child hydrated while their mouth is sore.
  • Usually normal when: Multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection
  • Call your doctor if: Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth
  • Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

This is one of the most common questions parents ask. Searching for answers means you care.

What Parents Should Know

According to AAP, NIH guidelines, herpetic gingivostomatitis is a common first-time infection with the herpes simplex virus (HSV-1) that causes painful sores on the gums, tongue, lips, and inside the cheeks. It is most common in children between 6 months and 5 years. While the sores look alarming and can make eating very painful for several days, the infection resolves on its own within 7-14 days. The main concern is keeping your child hydrated while their mouth is sore. At 0-6 months, hSV infection in babies under 6 months is uncommon but can be more serious due to their immature immune system. Neonatal herpes (contracted during birth) is a separate, more urgent condition. If a very young baby develops mouth sores with fever, seek medical evaluation promptly. Avoid kissing a baby if you have an active cold sore. It is generally considered normal when multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection. However, you should contact your pediatrician promptly if your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection
Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth
High fever (102-104F / 39-40C) for 3-5 days at the start of the illness
A baby under 3 months develops any mouth sores or blisters with fever
Heavy drooling and refusal to eat due to mouth pain
Your child has sores near or in the eyes, which can cause serious eye infection
Swollen, red gums that may bleed when touched
Your child has a weakened immune system and develops mouth sores

When to Seek Immediate Care

  • Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth
  • A baby under 3 months develops any mouth sores or blisters with fever
  • Your child has sores near or in the eyes, which can cause serious eye infection
  • Your child has a weakened immune system and develops mouth sores
  • Your child becomes very lethargic, difficult to wake, or has a stiff neck

By Age

What to expect by age

0-6 months

HSV infection in babies under 6 months is uncommon but can be more serious due to their immature immune system. Neonatal herpes (contracted during birth) is a separate, more urgent condition. If a very young baby develops mouth sores with fever, seek medical evaluation promptly. Avoid kissing a baby if you have an active cold sore.

6-12 months

This is a common age for a first HSV-1 infection, often acquired from a family member's cold sore through kisses or shared utensils. The infection starts with a fever of 102-104F (39-40C), followed by painful sores appearing on the gums, tongue, and inner cheeks. Gums may become very red, swollen, and bleed easily. Your baby will likely drool heavily and refuse to eat. Cool liquids, cold foods, and pain medication can help.

1-3 years

Toddlers with gingivostomatitis may have 10-20 painful ulcers in the mouth at once. They will often refuse all food and most drinks. Popsicles, cold milk, yogurt, and smoothies are often better tolerated than warm foods. The worst pain is typically days 2-5, with gradual improvement after that. After this primary infection, the virus stays dormant and may occasionally cause cold sores later in life.

What to Tell Your Pediatrician

  • Describe when you first noticed herpetic gingivostomatitis (mouth sores) in babies and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is drinking very little and you are concerned about dehydration.
  • Mention if fever persists beyond 5-7 days.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection
  • High fever (102-104F / 39-40C) for 3-5 days at the start of the illness
  • Heavy drooling and refusal to eat due to mouth pain
  • Swollen, red gums that may bleed when touched
  • Sores that take 7-14 days to fully heal
Mention at your next visit when...
  • Your child is drinking very little and you are concerned about dehydration
  • Fever persists beyond 5-7 days
  • Mouth sores have not started to heal after 10 days
  • Your child has recurrent episodes of mouth sores
Act now when...
  • Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth
  • A baby under 3 months develops any mouth sores or blisters with fever
  • Your child has sores near or in the eyes, which can cause serious eye infection
  • Your child has a weakened immune system and develops mouth sores
  • Your child becomes very lethargic, difficult to wake, or has a stiff neck

What You Can Do at Home

  • Keep track of when you notice herpetic gingivostomatitis (mouth sores) in babies — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection — this is generally within the range of normal.
  • At 0-6 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth.

Baby Oral Thrush (Mouth Yeast Infection)

Oral thrush is a common yeast infection (Candida) that causes creamy white patches on the tongue, gums, and inner cheeks. Unlike milk residue, thrush patches do not easily wipe away. It is very common in babies under 6 months, is usually mild, and is easily treated with a prescribed antifungal medication.

Hand, Foot, and Mouth Disease in Babies

Hand, foot, and mouth disease (HFMD) is a very common viral illness in babies and toddlers, especially during summer and fall. It causes small blisters or sores in the mouth and a spotted rash on the hands and feet. While it can make your child uncomfortable for a few days, it is not dangerous and resolves on its own within 7-10 days.

Baby White Tongue - Milk Residue or Thrush?

A white tongue in babies is extremely common and is usually just milk residue from breastfeeding or formula feeding. Milk residue coats the tongue lightly and can be wiped away with a damp cloth. Thrush (oral candidiasis) is a yeast infection that creates white patches that look like cottage cheese and do NOT wipe away easily - if you try, the tissue underneath may appear raw or bleed. Thrush can also appear on the cheeks, gums, and roof of the mouth.

Is My Baby Dehydrated?

Dehydration in babies happens when they lose more fluids than they take in, usually from vomiting, diarrhea, fever, or inadequate feeding. Key signs include fewer than six wet diapers in 24 hours, no tears when crying, a dry mouth, sunken fontanelle (soft spot), and unusual drowsiness. Mild dehydration can often be managed at home with extra fluids, but moderate to severe dehydration requires prompt medical attention.

Triage

Fever Decision Tree

Step-by-step guidance for evaluating your baby's fever by age and temperature.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is herpetic gingivostomatitis (mouth sores) in babies normal?
Herpetic gingivostomatitis is a common first-time infection with the herpes simplex virus (HSV-1) that causes painful sores on the gums, tongue, lips, and inside the cheeks. It is most common in children between 6 months and 5 years. While the sores look alarming and can make eating very painful for several days, the infection resolves on its own within 7-14 days. The main concern is keeping your child hydrated while their mouth is sore.
When should I call the doctor about herpetic gingivostomatitis (mouth sores) in babies?
Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth A baby under 3 months develops any mouth sores or blisters with fever Your child has sores near or in the eyes, which can cause serious eye infection
When is herpetic gingivostomatitis (mouth sores) in babies normal?
Multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection High fever (102-104F / 39-40C) for 3-5 days at the start of the illness Heavy drooling and refusal to eat due to mouth pain
What causes herpetic gingivostomatitis (mouth sores) in babies?
Herpetic gingivostomatitis is a common first-time infection with the herpes simplex virus (HSV-1) that causes painful sores on the gums, tongue, lips, and inside the cheeks. It is most common in children between 6 months and 5 years. While the sores look alarming and can make eating very painful for several days, the infection resolves on its own within 7-14 days. The main concern is keeping your child hydrated while their mouth is sore. Common explanations include: Multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection. High fever (102-104F / 39-40C) for 3-5 days at the start of the illness.
What should I mention to my pediatrician about herpetic gingivostomatitis (mouth sores) in babies?
You should mention herpetic gingivostomatitis (mouth sores) in babies at your next visit if: Your child is drinking very little and you are concerned about dehydration. Fever persists beyond 5-7 days. Mouth sores have not started to heal after 10 days.
Is herpetic gingivostomatitis (mouth sores) in babies normal at 0-6 months?
HSV infection in babies under 6 months is uncommon but can be more serious due to their immature immune system. Neonatal herpes (contracted during birth) is a separate, more urgent condition. If a very young baby develops mouth sores with fever, seek medical evaluation promptly. Avoid kissing a baby if you have an active cold sore.
Is herpetic gingivostomatitis (mouth sores) in babies normal at 6-12 months?
This is a common age for a first HSV-1 infection, often acquired from a family member's cold sore through kisses or shared utensils. The infection starts with a fever of 102-104F (39-40C), followed by painful sores appearing on the gums, tongue, and inner cheeks. Gums may become very red, swollen, and bleed easily. Your baby will likely drool heavily and refuse to eat. Cool liquids, cold foods, and pain medication can help.
Should I go to the ER for herpetic gingivostomatitis (mouth sores) in babies?
Seek emergency care if your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth, or if a baby under 3 months develops any mouth sores or blisters with fever. When in doubt, call your pediatrician's after-hours line for guidance.
Does herpetic gingivostomatitis (mouth sores) in babies go away on its own?
In many cases, herpetic gingivostomatitis (mouth sores) in babies resolves on its own, especially when multiple small, shallow ulcers on the gums, tongue, and inner cheeks during the first HSV-1 infection. By 1-3 years, toddlers with gingivostomatitis may have 10-20 painful ulcers in the mouth at once. They will often refuse all food and most drinks. Popsicles, cold milk, yogurt, and smoothies are often better tolerated than warm foods. The worst pain is typically days 2-5, with gradual improvement after that. After this primary infection, the virus stays dormant and may occasionally cause cold sores later in life.
AAPAAPNIH

References

  1. [1]American Academy of Pediatrics. Herpes Simplex Virus. Red Book Online. AAP
  2. [2]American Academy of Pediatrics. Cold Sores in Children. HealthyChildren.org. AAP
  3. [3]National Library of Medicine. Herpetic Gingivostomatitis. StatPearls. NIH

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Herpetic Gingivostomatitis (Mouth Sores) in Babies.

Things to mention

  • Describe when you first noticed herpetic gingivostomatitis (mouth sores) in babies and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child is drinking very little and you are concerned about dehydration.
  • Mention if fever persists beyond 5-7 days.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child is drinking very little and you are concerned about dehydration
  • Fever persists beyond 5-7 days
  • Mouth sores have not started to heal after 10 days

Urgent signs to report immediately

  • Your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth
  • A baby under 3 months develops any mouth sores or blisters with fever
  • Your child has sores near or in the eyes, which can cause serious eye infection

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Fever TriageTeething GuideWell-Baby Visit PrepMedicine Dosage CalculatorEmergency ContactsBaby Tracker

Bottom line

Most cases of herpetic gingivostomatitis (mouth sores) in babies are normal. Talk to your pediatrician if your child shows signs of dehydration: no wet diapers for 6+ hours, no tears, sunken fontanelle, or dry mouth.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Baby Oral Thrush (Mouth Yeast Infection)

Oral thrush is a common yeast infection (Candida) that causes creamy white patches on the tongue, gums, and inner cheeks. Unlike milk residue, thrush patches do not easily wipe away. It is very common in babies under 6 months, is usually mild, and is easily treated with a prescribed antifungal medication.

Hand, Foot, and Mouth Disease in Babies

Hand, foot, and mouth disease (HFMD) is a very common viral illness in babies and toddlers, especially during summer and fall. It causes small blisters or sores in the mouth and a spotted rash on the hands and feet. While it can make your child uncomfortable for a few days, it is not dangerous and resolves on its own within 7-10 days.

Baby White Tongue - Milk Residue or Thrush?

A white tongue in babies is extremely common and is usually just milk residue from breastfeeding or formula feeding. Milk residue coats the tongue lightly and can be wiped away with a damp cloth. Thrush (oral candidiasis) is a yeast infection that creates white patches that look like cottage cheese and do NOT wipe away easily - if you try, the tissue underneath may appear raw or bleed. Thrush can also appear on the cheeks, gums, and roof of the mouth.

Is My Baby Dehydrated?

Dehydration in babies happens when they lose more fluids than they take in, usually from vomiting, diarrhea, fever, or inadequate feeding. Key signs include fewer than six wet diapers in 24 hours, no tears when crying, a dry mouth, sunken fontanelle (soft spot), and unusual drowsiness. Mild dehydration can often be managed at home with extra fluids, but moderate to severe dehydration requires prompt medical attention.

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