TL;DR
Canker sores in children are common — RAS affects up to 20% of the population and often starts in childhood or adolescence. The cause is the same immune-mediated mechanism as in adults, with a few pediatric-specific considerations: nutritional deficiency from picky eating (B12, zinc, iron, folate), first presentation may warrant celiac screening, and PFAPA syndrome is a diagnosis to know if your child has periodic fever episodes alongside the mouth sores. Treatment options are more limited in younger children — topical benzocaine is not recommended under age 2, and prescription steroids require a pediatrician or dentist's guidance. Salt water rinse and barrier patches are safe at any age. SLS-free toothpaste is the highest-evidence preventive measure and safe for all ages.
Are Canker Sores Normal in Children?
Yes. Recurrent aphthous stomatitis begins in childhood or adolescence in many people — studies estimate onset before age 20 in the majority of adult RAS sufferers. A child getting occasional canker sores is common and not inherently a sign of an underlying condition.
What changes with age: young children may have more difficulty tolerating the discomfort, more difficulty communicating about it, and more risk from refusing food or fluids during a painful episode. The cause, mechanism, and healing timeline are the same as for adults.
Causes More Relevant in Children
Nutritional Deficiency from Picky Eating
B12, zinc, iron, and folate deficiencies are among the most evidence-backed canker sore drivers in all ages. In children, selective eating habits (picky eating) create a higher risk of these deficiencies than in most adults with access to varied diets.
- B12: Almost exclusively in animal products. A child who avoids meat, eggs, and dairy is at high risk.
- Zinc: Found in red meat, shellfish, and legumes — all commonly avoided by picky eaters.
- Iron: Red meat and leafy greens are the best sources; many children eat little of either.
- Folate: Dark leafy greens are the richest source — not typical in a child's preferred foods.
If your child has frequent canker sores and a restricted diet, pediatric testing of B12, ferritin (iron stores), zinc, and folate is the highest-yield first step. A pediatrician can order this panel.
First Presentation of Celiac Disease
Recurrent aphthous stomatitis can be the presenting sign of celiac disease — the autoimmune response to gluten that damages the small intestine and impairs absorption of B12, folate, and iron. Celiac disease often presents in childhood, and the GI symptoms (diarrhea, bloating, poor growth) may be mild or absent while oral manifestations are prominent.
If a child has recurrent canker sores, no obvious nutritional deficiency from diet, and no other explanation — celiac screening (tissue transglutaminase IgA antibody) is appropriate. Crucially: do not start a gluten-free diet before testing. A gluten-free diet produces a false-negative celiac test. Test first.
See Gluten and Canker Sores for the full celiac connection.
PFAPA Syndrome
PFAPA stands for: Periodic Fever, Aphthous ulcers, Pharyngitis, Adenitis (swollen lymph nodes). It is a pediatric autoinflammatory syndrome — the most common cause of periodic fever in young children — characterized by recurring episodes roughly every 3–8 weeks of:
- Fever (typically 39–40°C / 102–104°F) lasting 3–7 days
- Aphthous ulcers in the mouth
- Sore throat (pharyngitis)
- Swollen lymph nodes in the neck (adenitis)
Between episodes, children are completely well. The pattern is strikingly regular — parents often report being able to predict the episodes on a calendar.
Who gets PFAPA: Primarily children under 5, though it can persist into later childhood. It's more common than often recognized and frequently goes undiagnosed for years as parents cycle through diagnoses of strep throat and viral illness.
Why it matters: PFAPA is not the same as standard canker sores — it's a systemic inflammatory syndrome in which aphthous ulcers are one component. Treatment approaches differ: a single dose of oral corticosteroid (prednisolone 1–2mg/kg) at fever onset typically aborts the episode within 24 hours. Tonsillectomy resolves PFAPA in a significant proportion of patients. Standard canker sore management does not address the underlying syndrome.
The diagnostic signal: The periodicity. If your child gets mouth sores AND fever on a predictable cycle every few weeks, raise PFAPA specifically with your pediatrician. A pediatric rheumatologist or immunologist can confirm the diagnosis.
Hormonal Onset (Adolescents)
RAS often worsens or first presents at puberty — hormonal changes during adolescence affect mucosal immune function. A teenager with new-onset frequent canker sores with no prior history is experiencing a common pattern. The approach is the same as for adult RAS: rule out nutritional deficiency, address SLS exposure, investigate systemic associations if frequent.
Treatment Limitations in Children
Salt Water Rinse — Safe at Any Age
Warm salt water rinse (1/4 tsp in 8oz warm water) is safe for children old enough to rinse and spit without swallowing. The main practical limitation is that young children (under 5–6) may not reliably spit rather than swallow. Swallowing small amounts of salt water isn't harmful, but the child's cooperation determines whether it's feasible.
Barrier Patches — Safe at Any Age
Canker Cover patches and similar dissolvable barrier patches are safe for children. No systemic absorption, no pharmaceutical ingredients. The practical challenge: younger children may remove the patch with their tongue almost immediately, and they dissolve over time regardless. Most useful in children who are old enough to tolerate leaving it in place.
Benzocaine — Age Restrictions Apply
Topical benzocaine products (Orajel, Anbesol) carry an FDA warning against use in children under 2 years due to the risk of methemoglobinemia — a condition in which benzocaine interferes with hemoglobin's ability to carry oxygen. For children under 2, benzocaine should not be used. For children aged 2 and older, brief occasional use for significant pain is generally considered low-risk, but use should be minimal and parents should read product labeling carefully.
Prescription Topical Steroids — Pediatrician Guidance Required
Triamcinolone in Orabase and fluocinonide gel are used in children for severe aphthous ulcers, but dosing, frequency, and appropriateness should be determined by a pediatrician or pediatric dentist. Topical steroid absorption in children — with their smaller body mass — deserves appropriate medical oversight.
SLS-Free Toothpaste — Safe at Any Age
Switching to SLS-free toothpaste is safe for children and is one of the most effective preventive measures available. The 64% reduction in canker sore frequency documented in clinical trials is not age-specific. For a child with recurrent canker sores, this is the first intervention to try.
When to See a Doctor
- Canker sores accompanied by fever — particularly if this is a repeating pattern every few weeks (PFAPA)
- Ulcers so painful the child refuses food or fluids for more than 24 hours
- More than 3 outbreaks per month
- Ulcer larger than 10mm or not healing within 3 weeks
- Any concern about nutritional deficiency — a pediatrician can order the relevant blood tests
- Recurrent canker sores in a child with any GI symptoms — warrant celiac screening