What Causes Canker Sores?

Canker sores (also called aphthous ulcers or aphthous stomatitis) are common small and painful ulcers that form inside the mouth, usually occurring on the tongue, inner lining of the cheeks or lips, and the throat. 

Canker sores are not the same as cold sores (fever blisters), which are an infection caused by the herpes virus.

Canker sores are oral ulcers with a characteristic appearance: 

• Round or oval shape
• Red rim
• Yellow colored fluid in center
• Size varies from smaller than 1 mm to larger than 1 cm
• Lesions usually start as a pinpoint-sized bump and develop into an ulcer over 1 to 2 days, reaching their largest size in 3 to 4 days before beginning to heal

A canker sore lesion usually starts as a pinpoint-sized bump and develops into an ulcer over 1 to 2 days, reaching its largest size in 3 to 4 days before starting to heal. Most of the time, canker sores go away on their own within 2 weeks. 

Treatment for canker sores is aimed at relieving pain, speeding healing, and decreasing their recurrence.

Topical anesthetics can provide fast relief for canker sore pain.  

Treatment for canker sores includes: 

• Proper oral hygiene
  • Brush regularly with a soft toothbrush
  • Floss regularly
  • Use a mouthwash that does not contain alcohol to help reduce microbial overgrowth
  • Avoid toothpastes that contain sodium lauryl sulfate (SLS) if that causes or aggravates sores
• Avoid behaviors that can injure the mouth
  • Don’t bite the inside of the lips or cheeks
  • Avoid foods that trigger sores 
  • Reduce sharp or rough edges on braces and dental restorations 
• Pain medicines
  • Topical anesthetics
• Topical corticosteroids for mild to moderate canker sores
• Topical antibiotics (mouth rinses, gels, or pastes) to control secondary infection 
• Vitamins and dietary supplements if there are diagnosed nutritional deficiencies (e.g., vitamin B12, folate, iron, zinc) 

For severe cases of canker sores that do not respond to traditional therapies, treatments may include: 

• Colchicine, taken with or without dapsone 
• Thalidomide: for severe canker sores and mucocutaneous lesions of Behçet syndrome and for oral ulcers in HIV patients
• Apremilast: helps inhibit production of proinflammatory cytokines 
• Montelukast: may relieve pain and improve healing of oral ulcers 
• Cyclosporine: used to treat mucocutaneous ulcers in patients with Behçet syndrome, and may be effective in patients with complex sores
• Biologic agents
  • Anti-tumor necrosis factor (TNF)-alpha agents, such as adalimumab, etanercept, infliximab, and golimumab have been used to treat severe and recalcitrant canker sores
  • Only used in patients who have disabling disease that has not responded to conservative measures
• Pentoxifylline: benefits may be limited
• Laser therapy: may help relieve canker sores but more study is needed