Are Canker Sores Contagious?

Canker sores are not contagious. Canker sores cannot be spread through saliva and are not transmitted by kissing, oral sex, or sharing toothbrushes or utensils with someone who has a canker sore.

Canker sores (also called aphthous ulcers or aphthous stomatitis) are small, painful ulcers inside the mouth. They are a common type of oral lesion that can occur 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. 

Are Canker Sores Contagious?

Canker sores are not contagious. Canker sores cannot be spread through saliva and are not transmitted by kissing, oral sex, or sharing toothbrushes or utensils with someone who has a canker sore.

What Are Symptoms of Canker Sores?

Canker sores are oral ulcers with a characteristic appearance: 

• Round to oval shape
• Red rim
• Yellowish fluid in center
• Can range in size from less than 1 mm to more than 1 cm
• Lesions usually progress from a pinpoint-sized bump into an ulcer over 1 to 2 days, reaching their largest size in 3 to 4 days before starting to heal

The cause of most canker sores is unknown. Possible causes of canker sores include: 

• Genetics: canker sores tend to run in families
• Stress
• Mouth injuries such as biting the inside of the lip or brushing the teeth too hard 
• Sodium lauryl sulfate (SLS), an ingredient in many toothpastes and mouthwashes
• Problems with the immune system 
• Nutritional deficiencies such as low iron or vitamin B12

Canker sores are diagnosed with a patient history and physical examination of the mouth. Most of the time, the appearance of the canker sores is sufficient to make the diagnosis. In severe or unusual cases, tests to confirm canker sores or rule out other conditions may include: 

• Biopsy 
• Blood tests
  • Complete blood count (CBC)
  • Erythrocyte sedimentation rate (ESR)
  • Nutritional deficiencies (e.g., vitamin B12, folate, iron)

Canker sore lesions usually progress from a pinpoint-sized bump into an ulcer over one to two days, reaching its largest size in three to four days before starting to heal. Most of the time, canker sores go away on their own within two weeks. 

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

Treatment for canker sores includes: 

• Maintaining good oral hygiene
  • Brush regularly using a soft toothbrush
  • Floss regularly
  • Use a non-alcohol-containing mouthwash to help decrease microbial overgrowth
  • Avoid toothpaste containing sodium lauryl sulfate (SLS) if that causes or aggravates sores
  • Less aggressive but more frequent professional dental cleanings are recommended
• Avoid habits that cause trauma to the mouth
  • Don’t bite the inside of the cheek or lips
  • Avoid foods that trigger sores
  • If possible, reduce sharp/rough edges on dental restorations or braces
• Pain medicines
  • Topical anesthetics for temporary relief of discomfort 
• Topical corticosteroids are the first-line treatment for patients with mild to moderate canker sores
• Topical antibiotics (mouth rinses, gels, or pastes) to control secondary infection in more extensive cases
• Vitamins and dietary supplements for patients who have a documented nutritional deficiency (e.g., vitamin B12, folate, iron, zinc) 

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

• Colchicine, with or without dapsone 
• Thalidomide: for severe aphthous stomatitis and the mucocutaneous lesions of Behçet syndrome and for oral ulcers in HIV patients
• Montelukast: may improve pain and healing of oral ulcers 
• Apremilast: inhibits production of proinflammatory cytokines 
• Pentoxifylline: may have limited benefits 
• Cyclosporine: used to treat mucocutaneous ulcers in patients with Behçet syndrome, and it might be effective in patients with complex aphthosis
• Biologic agents
  • Anti-tumor necrosis factor (TNF)-alpha agents, including etanercept, adalimumab, infliximab, and golimumab, have all been successfully used to treat severe and recalcitrant canker sores
  • Reserved for patients with disabling disease that has failed to respond to more conservative measures
• Laser therapy: may help but more study is needed