My Baby Has Mouth Ulcers or Sores
The short answer
Mouth ulcers (canker sores or aphthous ulcers) are common in babies and toddlers and appear as small, round or oval sores with a white or yellowish center and red border on the inner cheeks, gums, tongue, or lips. They are usually caused by minor injuries (biting, sharp foods), viral infections (like hand-foot-and-mouth disease or herpes simplex), or sometimes nutritional deficiencies. Most heal on their own within 7-14 days, but they can cause significant pain and feeding difficulties.
This is one of the most common questions parents ask. Searching for answers means you care.
By Age
What to expect by age
0-6 months
Mouth sores in very young infants are less common but can occur. Thrush (oral candidiasis) is the most frequent cause of white patches in an infant's mouth and is caused by yeast, not ulcers — it appears as white patches that do not wipe off easily. Neonatal herpes (from HSV infection) can cause mouth sores in newborns and is a serious condition requiring immediate treatment. Epstein pearls (small, white, harmless cysts on the gums or roof of the mouth) are very common in newborns and resolve without treatment. If your young infant has mouth sores and seems unwell, has a fever, or is not feeding, seek prompt medical evaluation.
6-12 months
Hand-foot-and-mouth disease (caused by coxsackievirus) is a common cause of mouth ulcers in babies, usually accompanied by a rash on the hands, feet, and buttocks. Primary herpes gingivostomatitis (first HSV-1 infection) causes multiple painful mouth sores, high fever, drooling, and refusal to eat. Canker sores (aphthous ulcers) can also begin at this age. For pain relief, offer cool foods and liquids, use infant acetaminophen or ibuprofen (for 6+ months), and keep your baby hydrated. Avoid acidic, salty, or spicy foods that can worsen pain.
12-36 months
Toddlers are prone to mouth injuries from falls, chewing on hard objects, or accidentally biting their cheeks or lips. These injuries can cause ulcers that heal within 1-2 weeks. Recurrent canker sores in toddlers may be related to vitamin deficiencies (iron, B12, folate), food sensitivities, or stress. If your toddler gets frequent mouth ulcers, your pediatrician may check bloodwork. For severe or widespread mouth sores, prescription treatments like oral acyclovir (for herpes) or magic mouthwash (a compounded rinse) may be recommended.
What Should You Do?
When to take action
- Your child has one or two small ulcers inside the mouth that appeared after a minor injury and are healing within 1-2 weeks.
- Mouth sores are mild, your child is still eating and drinking adequately, and there is no fever.
- Your child has hand-foot-and-mouth disease with mouth ulcers that are healing within 7-10 days.
- Your child has recurrent mouth ulcers (more than 3-4 episodes per year) and you want to identify potential causes.
- Mouth sores are making it very difficult for your child to eat or drink.
- Mouth ulcers are accompanied by sores on other parts of the body or unusual symptoms.
- Your newborn (under 3 months) has mouth sores, fever, or is refusing to eat — this could be neonatal herpes, which is a medical emergency requiring immediate treatment with antiviral medication.
- Your child has mouth sores with signs of dehydration: no wet diapers for 6+ hours, dry mouth, no tears, sunken fontanelle, or lethargy — seek medical care.
- Your child has widespread mouth ulcers with high fever, extreme pain, and is completely unable to swallow — seek urgent medical evaluation.
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
Worrying about your baby means you care. That is a good thing.
Related Medical Concerns
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 Tongue Tie (Ankyloglossia)
Tongue tie occurs when the strip of tissue (frenulum) connecting the tongue to the floor of the mouth is shorter or tighter than usual, potentially restricting tongue movement. It is present in about 4-10% of newborns. Many tongue ties cause no problems at all, but when they do, feeding difficulties (especially breastfeeding) are the most common concern.
My Baby Is Fussy and Irritable During Feedings
Fussiness during feeding is very common and can have many causes, most of them manageable. Common reasons include gas, reflux, fast or slow milk flow, overtiredness, overstimulation, ear infections, teething, or food sensitivities. While occasional fussy feeding is normal, persistent distress during every feeding, especially if accompanied by poor weight gain, arching, or refusal to eat, should be evaluated by your pediatrician to rule out conditions like reflux, milk protein allergy, or tongue tie.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.
Adenoid Hypertrophy and Breathing
Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.