By Dr. Keerthi Sudireddy
Cold sores and canker sores are often confused, but they are completely different. Knowing which is which helps you treat them correctly.
Quick answer
Canker sores (mouth ulcers) appear inside the mouth, are not contagious, and come from minor injury, stress or certain foods. Cold sores appear on or around the lips, are caused by the herpes simplex virus, and are contagious. Canker sores heal on their own in one to two weeks; cold sores crust and heal in a similar time, helped by antiviral creams. See a dentist or doctor if sores are severe or persistent.
Canker sores (mouth ulcers)
- Inside the mouth (cheeks, tongue, gums).
- Not contagious; from injury, stress or foods.
- Heal in one to two weeks.
Cold sores
- On or around the lips.
- Caused by the herpes simplex virus; contagious.
- Helped by antiviral creams.
See our mouth ulcers guide. If a sore lasts over three weeks, get it checked at The Tooth Studio.
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