What could cause sores inside a 2-year-old's (two-year-old) mouth?

Mouth Sores in a 2-Year-Old: Differential Diagnosis and Management

The most common causes of mouth sores in a 2-year-old are primary herpes simplex virus (HSV) gingivostomatitis, hand-foot-and-mouth disease (viral), aphthous ulcers (canker sores), and traumatic lesions, with HSV being the most clinically significant due to its severity and potential complications. 1

Primary Diagnostic Considerations

Herpes Simplex Virus (HSV) Gingivostomatitis

This is the most important diagnosis to consider in young children with mouth sores due to its severity and need for specific treatment:

• Clinical presentation: Fever, irritability, tender submandibular lymphadenopathy, and superficial, painful ulcers in the gingival and oral mucosa and perioral area characterize primary HSV gingivostomatitis 1
• Vesicular lesions: Look for vesicles that rupture into painful ulcers, often with perioral involvement 1
• Systemic symptoms: Children typically appear more systemically ill with high fever and difficulty eating/drinking 1
• Diagnosis: Clinical diagnosis based on typical appearance; viral culture can confirm if needed (results in 1-3 days) 1

Viral Pharyngitis/Stomatitis (Non-HSV)

• Most cases of mouth sores in young children are viral and self-limited 2
• Hand-foot-and-mouth disease commonly presents with oral ulcers in this age group 3

Aphthous Stomatitis (Canker Sores)

• Common, relatively benign lesions that occur in young children 3
• Typically recurrent, painful ulcers without systemic symptoms 3, 4
• Self-limited and do not require specific antiviral therapy 4

Traumatic Lesions

• Consider accidental trauma from toys, utensils, or self-inflicted injury 5
• Usually isolated lesions without systemic symptoms 5

Red Flags Requiring Urgent Evaluation

Immediately assess for these concerning features:

• Toxic appearance: May indicate diphtheria, parapharyngeal/retropharyngeal abscess, or severe HSV infection requiring hospitalization 2
• Difficulty swallowing or drooling: Suggests severe involvement or airway compromise 5
• Dehydration: Common complication when painful lesions prevent adequate oral intake 1
• Immunocompromised state: HSV can cause severe local lesions or disseminated disease with visceral involvement 1

Management Approach

For Suspected HSV Gingivostomatitis:

• Antiviral therapy: Acyclovir is the drug of choice for HSV treatment in children 1
• Oral acyclovir can be used for primary gingivostomatitis in immunocompetent children 1
• Pain management: Critical for maintaining hydration and nutrition 1
  • Oral acetaminophen for systemic pain control 1
  • Cautious use of topical 2.5% lidocaine ointment may be effective 1

For Viral Stomatitis (Non-HSV):

• Supportive care with pain management 2
• Ensure adequate hydration 2
• Symptoms typically resolve within a few days 1

For Aphthous Ulcers:

• Supportive care and pain management 3
• Reassurance that lesions are self-limited 4

Important Clinical Pearls

Group A Streptococcal (GAS) pharyngitis is uncommon in this age group:

• GAS infection in children <3 years old is often associated with fever, mucopurulent rhinitis, excoriated nares, and diffuse adenopathy, but exudative pharyngitis is rare 1
• The low prevalence of GAS pharyngitis and low risk of acute rheumatic fever in children <3 years limits the usefulness of diagnostic testing 1
• Reports of acute rheumatic fever in children <3 years are very rare 1

Teething does not cause mouth sores:

• While teething typically begins around 6 months of age, it causes gingival discomfort but not ulcerative lesions 6
• If "teething" is blamed for mouth sores, look for alternative diagnoses 6

When to Refer or Hospitalize

• Toxic appearance or signs of systemic infection 2
• Inability to maintain hydration 1
• Suspected immunodeficiency with severe or recurrent lesions 3
• Lesions causing airway compromise or significant feeding difficulties 5
• Failure to improve with appropriate management 2