Common Causes of Canker Sores in Children
Canker sores (recurrent aphthous stomatitis) in children are primarily caused by nutritional deficiencies—particularly vitamin B12, folate, iron, and zinc—along with local trauma, immune dysfunction, and in severe cases of malnutrition, systemic factors that impair oral mucosal immunity.
Nutritional Deficiencies
Micronutrient Deficiencies
- Vitamin B12 and folate deficiencies are significantly associated with recurrent aphthous stomatitis, with affected patients demonstrating markedly lower dietary intakes of these vitamins compared to healthy controls 1
- Iron deficiency commonly coexists with B12 and folate deficiencies and can lead to anemia, which impairs mucosal healing and increases susceptibility to oral lesions 2, 3
- Zinc deficiency is particularly important in children, as it impairs oral mucosal immunity and wound healing; severely malnourished children show plasma zinc levels below 10.8 micromol/L 4, 5
- Vitamin C (ascorbate) deficiency reduces collagen synthesis and mucosal integrity, with levels below 11 micromol/L associated with oral mucosal problems 4, 3
- Vitamin A (retinol) deficiency affects epithelial integrity and immune function, with levels below 1.05 micromol/L seen in malnourished children with oral lesions 4, 5
Protein-Energy Malnutrition
- General malnutrition causes functional and structural alterations in mucosal barriers, leading to chronic inflammation and impaired healing 2
- Essential amino acid deficiencies compromise tissue repair and immune function, making oral mucosa more vulnerable to ulceration 4
- Malnutrition is particularly common in children with chronic inflammatory conditions, affecting up to 40% and causing growth retardation 2, 6
Non-Nutritional Factors
Local Trauma and Mechanical Factors
- Physical trauma from dental appliances, aggressive tooth brushing, or accidental biting triggers lesions at sites of injury, particularly when underlying mucosal integrity is compromised 7
- Increased viscosity of oral submucosal extracellular matrix at trauma sites heightens inflammatory response and ulcer formation 7
Immune and Inflammatory Factors
- Weakened immune system from any cause increases susceptibility to oral infections and poor mucosal healing 2
- Chronic intestinal inflammation and epithelial damage from conditions like inflammatory bowel disease create systemic immune dysregulation affecting oral mucosa 2, 8
- Microbial translocation and systemic immune activation in malnourished children further impair mucosal immunity 2
Dietary Triggers
- Food sensitivities including gluten (in celiac disease patients) and other specific foods can trigger lesions in susceptible individuals 7
- Lectins and other food substances may penetrate oral mucosa and influence underlying tissue integrity 7
Clinical Implications
Assessment Priorities
- Screen for malnutrition at presentation using validated tools, as documented malnutrition worsens prognosis and quality of life 2, 6
- Evaluate specific micronutrient status through dietary history and laboratory assessment for B12, folate, iron, zinc, and vitamin levels when recurrent canker sores are present 2, 6
- Assess growth parameters in children, as growth failure may indicate chronic malnutrition even when not immediately obvious from basic measurements 2, 6
Common Pitfalls
- Do not overlook micronutrient deficiencies in children who appear adequately nourished by weight alone, as covert deficits in specific nutrients can exist 2
- Inflammatory markers may confound interpretation of nutritional biomarkers like ferritin, requiring additional testing such as soluble transferrin receptor for accurate iron status assessment 2
- Regular nutritional screening is essential for children with chronic diseases, as early detection prevents adverse outcomes including persistent oral lesions 6