What is the cause and treatment of canker sores (also known as aphthous ulcers)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: June 12, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Canker sores, also known as aphthous ulcers, are caused by a combination of local and systemic factors, including traumatic, infectious, allergic factors, and may be associated with skin disease, autoimmune disease, tumor, inflammatory bowel disease, and so on, although the exact cause is often unknown 1. The diagnosis and treatment of canker sores are tasks of oral specialists, and their management can be challenging due to the diversity and complexity of oral ulcerations.

Causes of Canker Sores

  • Traumatic factors, such as minor injuries
  • Infectious factors
  • Allergic factors
  • Association with skin disease, autoimmune disease, tumor, inflammatory bowel disease, and so on
  • Possibly immune system reactions, genetic predisposition, nutrient deficiency, oral trauma, anxiety or stress, as seen in recurrent aphthous ulcers (RAU) 1

Treatment of Canker Sores

  • Most canker sores heal on their own within 1-2 weeks, but several options can help manage pain and speed healing, including over-the-counter topical products containing benzocaine or hydrogen peroxide, and rinsing with salt water or a solution of equal parts hydrogen peroxide and water several times daily.
  • Prescription options include topical steroids like triamcinolone dental paste, antimicrobial mouthwashes containing chlorhexidine or tetracycline, or stronger pain relievers
  • Avoiding spicy, acidic, or rough-textured foods during healing can prevent further irritation
  • Good oral hygiene, including gentle brushing with a soft-bristled toothbrush and regular flossing, helps prevent secondary infections If canker sores are unusually large, last longer than three weeks, recur frequently, or are accompanied by fever or severe pain, medical evaluation is recommended as they may indicate an underlying health condition.

From the Research

Causes of Canker Sores

  • The exact cause of canker sores (also known as aphthous ulcers) is not well understood, but several factors are thought to contribute to their development, including minor mouth injury, stress, and certain foods 2.
  • Hard, acidic, and salty foods, as well as toothpastes containing sodium lauryl sulfate, may trigger canker sores 2.
  • Alcohol and carbonated drinks may also contribute to the development of canker sores 2.

Treatment of Canker Sores

  • Topical agents, such as local anesthetics (e.g., lidocaine, benzocaine) and antiseptic/anti-inflammatory agents (e.g., triclosan, diclofenac), are commonly used to treat canker sores 3, 2, 4.
  • Corticosteroids may be used to treat more severe cases of canker sores 2.
  • Amlexanox 5% paste has been shown to be effective in reducing ulcer size, pain duration, and healing time 5.
  • Hyaluronic acid-based products, such as barrier forming mouth rinses or topical gels, may also be effective in treating canker sores 6.
  • Treatment of canker sores is typically symptomatic and tailored to the individual case, taking into account the frequency of ulcers, intensity of pain, and responsiveness to treatment 2.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.