Can You Pop a Canker Sore? What to Do Instead

Do not pop a canker sore. Unlike a blister or pimple, it isn’t fluid-filled, so there’s nothing to squeeze out. Picking at the open sore only makes it more painful.

Canker sores are painful but not typically dangerous, and most go away on their own within a week or two. Read on to learn why canker sores have a white center, what to do if you popped one, which bumps hold fluid and what helps.

What’s Inside a Canker Sore?

A canker sore, or aphthous ulcer, is a shallow break in your mouth’s lining and one common type of mouth ulcer. It’s not a fluid-filled blister, so there’s nothing to squeeze out.

Why the Center Looks White or Yellow

A canker sore’s white, yellow, or gray center isn’t pus. It’s a thin covering made mostly of fibrin, a protein your body lays over open sores. A white center alone doesn’t mean infection, even if it looks like a whitehead.

How a Canker Sore Forms and Heals

Canker sores usually follow this pattern:

• You may feel a tingling or burning sensation for a day or two before the ulcer forms.
• The sore is usually round or oval.
• It’s white, yellow, or gray in the middle with a red border.

Most canker sores heal on their own within 1 to 2 weeks.¹ The pain often goes away sooner, within 7 to 10 days.

Major canker sores, larger than 1 centimeter, may take several weeks or more to heal and typically leave scars.

See your doctor or dentist if the canker sore doesn’t go away after 2 weeks. Some serious conditions can resemble a canker sore at first, including oral cancer.

Why Popping a Canker Sore Makes It Worse

When you squeeze, poke, or pick a canker sore, there’s nothing to drain. You’re ripping off the fibrin layer, leaving the tissue underneath raw and more painful. Injury inside your mouth is a known trigger for canker sores.

Popping, picking or scraping a canker sore can:

• Make it sorer, redder and more swollen
• Cause bleeding
• Leave the sore harder to heal
• Carry in bacteria from your fingers or a pin, since canker sores can pick up a bacterial infection

What to Do If You Already Popped It

If you already popped it, don’t panic. It’ll probably still go away on its own. For the next few days, try:

• Rinsing your mouth with warm salt water a few times a day
• Keeping your tongue, fingers, and toothbrush off the sore
• Eating soft, bland, lukewarm foods
• Seeing your dentist or doctor if the sore gets worse or you develop a fever

Is It a Canker Sore or a Blister?

Canker sores aren’t filled with fluid. A raised bump filled with fluid or blood isn’t a canker sore, but you still shouldn’t pop it.

Are Canker Sores Contagious?

Unlike cold sores, canker sores are not contagious. They’re not caused by the herpes virus, so you can’t spread them through kissing or sharing a cup.

Cold Sore (Fever Blister)

Cold sores are small fluid-filled blisters caused by the herpes simplex virus, usually HSV-1. They usually occur on or around your lips, but the virus can also cause blisters and sores inside your mouth. A sore on the outside of your lip is more likely a cold sore, since canker sores only occur inside your mouth.

Cold sores are very contagious while you have symptoms, and the virus can spread even when you have none. Don’t touch one, wash your hands after contact, keep your hands away from your eyes and avoid kissing or oral sex during an outbreak. Doctors treat them with prescription antiviral cream or pills.

Blood Blister

Blood blisters in your mouth are red, purple, or black and usually caused by an injury, such as biting your cheek.

Many break open on their own, but don’t pop them. See your dentist or doctor, since some have other causes.

Mucous Cyst

Mucous cysts, also called mucoceles, are painless, clear or bluish fluid-filled bumps. They usually form inside the lower lip and are often caused by biting your lip, which damages a salivary gland.

Most go away on their own, but your dentist can remove one that keeps coming back. Draining or removing one yourself could cause an infection or damage the area.

What to Do Instead of Popping a Canker Sore

There’s no quick fix for canker sores, but these steps help with the pain.

1. Rinse With Salt Water or Baking Soda

Rinse your mouth several times a day with ½ teaspoon of table salt in 8 ounces of warm water, then spit it out. For a baking soda rinse, use 1 teaspoon in ½ cup of warm water.

2. Apply Hydrogen Peroxide and Milk of Magnesia

Mix equal parts of water and 3% hydrogen peroxide labeled for oral use. Dab a little on the sore with a cotton swab, then add a tiny dab of milk of magnesia.

Do these steps three or four times a day for up to seven days, unless your dentist or doctor says otherwise. Don’t use the peroxide straight from the bottle, and don’t swallow it. Stop if the irritation gets worse.

Ask a dentist or doctor before using it on a child under 2, and watch older children while they use it.

3. Use a Numbing Gel or Protective Paste

Apply an over-the-counter benzocaine gel to numb the sore, or try a paste that coats it to reduce pain from foods.

Don’t use benzocaine products in children under 2. Benzocaine can cause a serious, potentially life-threatening drop in the oxygen your blood carries.¹⁰

Stop using benzocaine and seek medical care right away if you or your child develop pale, gray or blue skin, shortness of breath or a racing heartbeat. For older children and adults, follow the label.

4. Take a Pain Reliever

Take acetaminophen or ibuprofen as the label directs, but avoid ibuprofen if it has triggered mouth sores for you.

5. Avoid Foods That Sting

Suck on ice chips or eat soft, cool foods. Stay away from:

• Spicy foods
• Citrus, tomatoes and other acidic foods and drinks
• Salty or crunchy snacks like chips
• Very hot drinks

6. Ask About Prescription Treatment

If your canker sores are large, happen often or are very painful, ask your dentist or doctor about prescription-strength medicines, such as:

• A steroid mouth rinse containing dexamethasone
• A corticosteroid gel or paste such as fluocinonide
• In-office chemical cautery or low-level laser therapy to ease pain
• Oral medicine for severe sores that don’t heal with other treatments

How to Prevent Canker Sores

Nothing completely prevents canker sores, but avoiding triggers may make them less frequent. Common triggers include:

• Mouth injuries from biting your cheek, dental work or brushing too hard (use a soft-bristled brush)
• Toothpaste or mouthwash with sodium lauryl sulfate (SLS), which can trigger sores in some people
• Spicy or acidic foods or foods you’re sensitive to
• Stress

Doctors call frequent canker sores recurrent aphthous stomatitis, a form of stomatitis (mouth inflammation).

Frequent sores have been linked to low iron, folate or vitamin B12, celiac disease and inflammatory bowel disease. Ask your doctor whether you need testing.

In one small study, 58 people with frequent canker sores took a vitamin B12 supplement or a placebo daily for six months. Those who took 1,000 mcg under the tongue had shorter outbreaks, fewer sores and less pain in the fifth and sixth months.¹¹ Ask your doctor before trying this.

When to See a Dentist or Doctor

See a dentist or doctor if a canker sore hasn’t healed in two weeks.³ A dentist is a good first stop, but if you also have a fever or rash or feel unwell, see a doctor.

See a Dentist or Doctor If You Have

• A sore that lasts two weeks or longer, whether or not it hurts
• An unusually large sore
• A sore that gets worse instead of better
• New sores before the old ones heal, or sores more than two or three times a year
• A sore that spreads onto the outer edge of your lip
• Pain that home care doesn’t control, or trouble eating or drinking
• A fever, skin rash, headache or diarrhea along with the sores
• Bleeding from a sore, or a lump, a red or white patch, or numbness in your mouth

Call your doctor or pediatrician right away if you can’t drink enough or have signs of dehydration. These include peeing much less than usual, a very dry mouth or no tears when a child cries.

See a dentist the same day for swelling in your cheek, jaw or gums, especially with a fever. Swelling with a fever but no clear dental cause needs medical care the same day.

Get Emergency Care or Call 911

Go to an emergency room if you have:

• Mouth sores or blisters with a red or purple rash that spreads, blistering or peeling skin, or burning eyes, especially after starting a new medicine
• Swelling that spreads quickly or moves toward your eye or down your neck, even without a fever
• A swollen or painful eye, or vision changes
• Trouble opening your mouth along with facial swelling
• Facial swelling with a fever when you can’t see a dentist right away

Call 911 if swelling makes it hard to breathe or swallow. Also call 911 if you or your child becomes confused, passes out or is hard to wake.