Are canker sores contagious? The truth about these painful ulcers.

What causes canker sores? Understanding the triggers.

Unlike cold sores, canker sores aren’t caused by a virus. Instead, they develop due to a mix of factors that irritate the inside of the mouth. 

These small ulcers typically appear on the inner cheeks, lips, gums, or tongue and while they’re not contagious, they can be incredibly painful.

Common triggers of canker sores.

• Minor mouth injuries. Accidentally biting your cheek, brushing too hard, or eating something sharp (like chips) can cause small wounds that turn into canker sores.
• Stress and hormonal changes. Feeling overwhelmed? Studies suggest that stress and hormonal shifts (like during menstruation) can weaken the immune system and trigger sores.
• Acidic and spicy foods. Citrus fruits, tomatoes, coffee and spicy meals can irritate sensitive tissues in the mouth, making you more prone to sores.
• Vitamin deficiencies. A lack of vitamin B12, iron, or folate has been linked to frequent canker sores. Your body needs these nutrients to repair and protect mouth tissue.
• Food sensitivities. Some people develop sores after eating gluten, dairy, or highly processed foods. If you notice a pattern, keeping a food journal might help pinpoint the cause.
• Underlying medical conditions. Canker sores can be a symptom of conditions like Celiac disease, Crohn’s disease, or an autoimmune disorder. If you get frequent or unusually large sores, it’s worth mentioning to your doctor.

Who gets canker sores the most?

Anyone can develop a canker sore, but some people are more prone to them. If you have a family history of frequent mouth ulcers, you might be more likely to experience them. Teens and young adults are also at a higher risk, though the reason isn’t fully understood.

Now, let’s answer the big question: Can canker sores spread from person to person?

Are canker sores contagious? Separating fact from fiction.

It’s a common myth that canker sores are contagious. Unlike cold sores, which are caused by the herpes simplex virus (HSV-1) and can spread through direct contact, canker sores don’t come from a virus or bacteria. 

That means you can’t pass canker sores to someone else through kissing, sharing utensils, or drinking from the same cup.

Canker sores vs. cold sores: key differences

Why do people confuse them?

Since both cause mouth pain, many people assume they’re the same. But while cold sores spread through direct contact, canker sores appear due to internal factors like stress, diet, or injury to the mouth.

Even though they’re not contagious, canker sores can still be frustrating—especially if they keep coming back. So, what can you do about them. Let’s go over the best ways to treat and prevent them.

How to treat and prevent canker sores at home.

Canker sores can be painful, but the good news is they usually heal on their own within 7 to 14 days. While there’s no instant cure, you can take steps to reduce pain, speed up healing and prevent future outbreaks.

How to relieve canker sore pain.

• Use a saltwater rinse. Mix ½ teaspoon of salt with warm water and swish it in your mouth for 30 seconds to help reduce swelling and promote healing.
• Try a baking soda rinse. Baking soda can neutralize acids in the mouth and soothe irritation. Mix 1 teaspoon of baking soda with warm water and rinse.
• Apply a numbing gel. Over-the-counter options like benzocaine (Orajel) or hydrogen peroxide-based rinses can provide quick pain relief.
• Avoid spicy and acidic foods. Citrus, tomatoes, vinegar and spicy meals can irritate the sore and make the pain worse.
• Use a soft-bristled toothbrush. Harsh brushing can aggravate the sore, so switch to a gentle toothbrush while it heals.

When do canker sores need medical attention?

Most canker sores heal without medical treatment, but in some cases, they may signal an underlying issue. See a doctor or visit CityMD if:

• The sore lasts longer than two weeks.
• You develop multiple sores at once.
• The sore is unusually large or extremely painful.
• You have difficulty eating or drinking due to pain.
• You experience fever, fatigue, or swollen lymph nodes along with the sore.

How to prevent future canker sores.

• Manage stress. Try relaxation techniques like deep breathing or meditation to reduce flare-ups caused by stress.
• Boost your diet. Eat foods rich in vitamin B12, iron and  folate to lower your risk of frequent sores.
• Avoid trigger foods. If spicy or acidic foods seem to bring on canker sores, limit them in your diet.
• Be gentle with your mouth. Use a soft toothbrush and avoid chewing on hard or sharp foods that could cause injury.
• Stay hydrated. A dry mouth can make sores worse, so drink plenty of water throughout the day.

When to visit CityMD for canker sores.

Canker sores might not be contagious, but they can become a real pain—literally. If your sore isn’t healing, keeps coming back, or makes eating difficult, CityMD urgent care is here to help. Our providers can assess your symptoms, rule out underlying conditions and recommend treatment options to help you heal faster.

Don’t let a canker sore disrupt your day. Walk into your nearest CityMD for quick, expert care today.