Baby Mouth Sores (Stomatitis): Causes, How to Tell Them Apart, and Dehydration Signs

Your baby is suddenly drooling, pushing away the bottle, and crying when anything touches their mouth. You look inside and see raw, whitish or red patches. That is stomatitis, and most cases clear up on their own. The thing that actually needs watching is not the ulcers themselves but whether the pain is stopping your child from drinking. Here is how to tell the common causes apart, what helps at home, and the exact signs that mean you should call a doctor.

What stomatitis actually means

Stomatitis is an umbrella term for inflammation of the lining of the mouth: the gums, the inside of the cheeks and lips, the roof of the mouth, and the tongue. It is not one disease but a group of them.

The causes split into two broad groups.

Infectious — caused by a virus or bacteria. Most cases in babies fall here.

Non-infectious — such as recurrent aphthous ulcers, the small round sores that come back in the same spots without any infection.

Telling the three common causes apart

Parents mostly want to know which one this is. In summer, three causes dominate, and they separate fairly well by where the ulcers sit and whether there is a rash outside the mouth.

	Herpangina	Hand, foot and mouth	Herpetic gingivostomatitis
Ulcer location	Mostly back of the throat	Tongue, gums, inner cheeks	Gums and throughout the mouth
Rash outside mouth	None	Palms, soles, buttocks	None (may appear around lips)
Fever	Sudden, over 39 degrees	Ulcers follow fever by 1 to 2 days	High fever before blisters
Gums	Usually normal	Usually normal	Swollen, bleed easily
Typical age	Under 4 years	Half of cases under 2	First infection, infants and toddlers

Herpangina starts with a sudden fever over 39 degrees and a sore throat. Red spots appear at the back of the throat, turn into blisters, and then become ulcers. It is most common under 4 years and peaks in summer.

Hand, foot and mouth disease begins with fever and sore throat, and 1 to 2 days later blister-like ulcers appear on the tongue, gums, and inner cheeks. A rash follows on the palms, soles, and buttocks, and it is usually not itchy. The NHS notes that it usually gets better on its own in 7 to 10 days.

Herpetic gingivostomatitis is what happens when a child meets the herpes simplex virus for the first time. According to The Royal Children's Hospital Melbourne, about one in four children develop mouth ulcers after that first infection. Swollen, easily bleeding gums are the giveaway.

💡 It is fine if you cannot tell them apart. What you do at home(fluids and pain control) is nearly identical for all three. Watching the dehydration signs below matters far more than naming the illness.

The real risk is dehydration, not the ulcers

When the mouth hurts, a child refuses not just food but fluids. That is the usual reason an otherwise self-limiting illness ends up needing medical care. Where oral intake becomes difficult and dehydration is a concern, supportive treatment including intravenous fluids may be needed.

The Royal Children's Hospital lists these signs.

Mild dehydration — passing urine less often, dark yellow or brown urine, dry lips, tongue, mouth or throat, dizziness or light-headedness

Severe dehydration — not passing urine at all, sunken eyes, no tears when crying

If you see mild signs, push fluids actively. If you see any severe sign, seek care straight away.

What helps at home

Fluids first, food later — The Royal Children's Hospital puts it plainly: there is no need to worry about a child not eating, but it is important that they get enough fluids. A few days of eating less is fine. Not drinking is not.

Cold and bland — Cold drinks and icy poles help. Acidic drinks such as orange juice, salty food, and hot food all sting the ulcers and make refusal worse.

Pain control — Paracetamol or ibuprofen can be used. A child who is not in pain will drink. Numbing gels are a decision for your doctor, not something to use on your own.

Little and often — Offering a lot at once invites refusal. Small amounts given frequently, by spoon or syringe, add up to more.

When to see a doctor

Seek medical care if any of the following apply.

• Your child keeps refusing fluids and shows the dehydration signs above
• An ulcer has not healed after 3 weeks — this is the NHS threshold
• An ulcer bleeds or becomes more painful and red, which can signal infection
• Fever persists alongside headache or vomiting

Enterovirus mouth infections can rarely be complicated by meningitis or myocarditis. This is uncommon, but if a fever drags on alongside headache or vomiting, do not wait. Note also that clinical guidance routinely lists dehydration itself among the complications of this illness.

Call emergency services if your child is difficult to wake, unusually confused, or extremely drowsy.

How long it lasts

The NHS notes that ordinary mouth ulcers clear up on their own within 1 to 2 weeks. Ulcers from herpetic gingivostomatitis can take 10 to 14 days, but the pain eases within 3 to 4 days. Hand, foot and mouth disease usually gets better on its own in 7 to 10 days.

In other words, the hard part is the first few days. Protect fluid intake through that window and time handles the rest.

Managing a mouth-sore week with BebeSnap

• Log feeds and fluid intake so you can see exactly how much went in today
• Track wet nappies so dehydration signs do not slip past you
• Record temperature and show the doctor the actual curve, not a guess
• Use AI stool analysis to follow bowel changes during a week of poor intake

Frequently Asked Questions (FAQ)

Q: How can I tell stomatitis from hand, foot and mouth disease?
A: The fastest check is to look outside the mouth. A rash on the palms, soles, or buttocks alongside mouth ulcers points to hand, foot and mouth disease. Ulcers concentrated at the back of the throat after a sudden fever above 39 degrees suggest herpangina, while swollen, easily bleeding gums suggest herpetic gingivostomatitis. Home care is the same for all three.

Q: My child will not drink because of the pain. When should I see a doctor?
A: Passing urine noticeably less often, urine turning dark yellow or brown, and dry lips and tongue are mild dehydration signs. No urine at all, sunken eyes, or no tears when crying mean you should seek care immediately. Pain is often the reason they will not drink, so give paracetamol or ibuprofen first and try again once it takes effect.

Q: How long do mouth sores take to heal?
A: Ordinary mouth ulcers heal on their own within 1 to 2 weeks. Herpetic gingivostomatitis ulcers can last 10 to 14 days, although the pain itself eases substantially within 3 to 4 days. Hand, foot and mouth disease usually gets better on its own in 7 to 10 days. An ulcer that has not healed after 3 weeks should be checked by a doctor.

Q: What should I feed a child with a sore mouth?
A: Cold and non-irritating options work best. Cold drinks, icy poles, and oral rehydration solutions all help. Avoid acidic drinks such as orange juice, salty foods, and hot foods, which sting the ulcers. Eating less for a few days is acceptable, but fluids are not optional, and small amounts offered frequently add up to more than large amounts offered at once.

References

• The Royal Children's Hospital Melbourne - Herpes simplex gingivostomatitis
• NHS - Mouth ulcers
• NHS - Hand, foot and mouth disease