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a close-up of aphthous ulcers on the inner lower lip and gum area showing red inflamed sores with white patches

Are Canker Sores Contagious? Ultimate Guide

If you’ve ever had a canker sore, you know how painful it can be. And if you’ve ever gotten one in a sensitive area like your mouth or tongue, you also know how inconvenient they can be. Canker sores are small ulcers that form on the soft tissues in your mouth, and they can make eating, talking, and even brushing your teeth a real pain.

Canker sores, or aphthous ulcers, are not contagious. They are a common problem, affecting about 20% of the population. Canker sores can occur on the inside of the cheeks, on the tongue, or the floor of the mouth. They are often preceded by a tingling or burning sensation. Canker sores are usually small and heal within two weeks. However, some canker sores can be large and painful and may take several weeks to heal with white stuff leaking from them.

Are canker sores contagious if you kiss?

a pink highlighter marking the text
Highlighting canker sores to explore if these mouth lesions are contagious.

No, canker sores are not contagious if you kiss. However, they can be painful, so it is best to avoid kissing if you have a canker sore. Canker sores are small ulcers that form on the soft tissues in your mouth, and they can make eating, talking, and even brushing your teeth a real pain. If you have a canker sore, several home remedies can help to speed the healing process and reduce pain.

Preventing canker sores

There is no surefire way to prevent canker sores. The only way is to make your immune system more robust and rinse your mouth with salt water.

However, there are several things you can do to reduce your risk of developing canker sores:

  • Avoid spicy, acidic, or salty foods that can irritate the soft tissues in your mouth.
  • Avoid chewing gum or eating hard candy.
  • Brush your teeth gently with a soft toothbrush.
  • If you wear dentures, ensure they fit correctly and clean them regularly.
  • If you have a history of canker sores, talk to your doctor about taking a daily multivitamin or using a mouth rinse that contains zinc or folic acid.

How to diagnose canker sore

Canker sores are usually small and heal within two weeks. However, some canker sores can be large and painful and may take several weeks to heal.

Canker sores and cold sores are not the same things. Cold sores are caused by the herpes simplex virus (HSV) and are contagious. Canker sores are not caused by a virus and are not infectious. Cold sores typically appear on the lips, whereas canker sores usually occur inside the mouth.

What is more contagious?

Is a canker sore more contagious than a cold sore?

A cold sore is more contagious than a canker sore. Cold sores are caused by the herpes simplex virus (HSV) and are contagious. Canker sores are not caused by a virus and are not infectious. Cold sores typically appear on the lips, whereas canker sores usually occur inside the mouth.

a close-up of aphthous ulcers on the inner lower lip and gum area showing red inflamed sores with white patches
Spot these inflamed sores to learn if canker sores are contagious.

Canker sores are not contagious. They are a common problem, affecting about 20% of the population. Canker sores can occur on the inside of the cheeks, on the tongue, or the floor of the mouth. They are often preceded by a tingling or burning sensation.

Both fever blisters and canker sores can have triggers that produce flare-ups. Try to identify and avoid triggers so your flare-ups become less frequent.

  • Sun exposure may sometimes trigger outbreaks of fever blisters. If you have recurring blisters, using sunscreen may help reduce their frequency.
  • Fever blisters are contagious. Avoid kissing, sharing eating utensils, cups, water bottles, or other items if you are experiencing symptoms.
  • Be aware that in young children, fever blisters can cause loss of appetite, drooling, and fever that can last for several days.
  • Talk to your doctor or your child’s pediatrician if symptoms are severe or recur frequently.
  • If you regularly get canker sores, talk to your doctor about testing for food allergies, as allergic reactions can sometimes trigger sore canker outbreaks.

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