How To Get Rid of a Canker Sore in 24 Hours?

You can’t reliably make a canker sore disappear in 24 hours, but you can reduce pain, limit irritation, and support healing with gentle rinses, cold foods or ice, protective products, and appropriate oral care. Most canker sores heal on their own within 1–2 weeks. Mayo Clinic

Medically Reviewed by Dr. Syra Hanif, M.D., Board-Certified Primary Care Physician

If you are searching for a way to get rid of a canker sore overnight, the first thing to know is that there is no reliable one-day cure. The useful goal for the first 24 hours is less pain, less irritation, and better conditions for the sore to heal.

Canker sores are also called aphthous ulcers. They are not the same as cold sores, are not caused by herpes, and are not contagious. NIDCR

What Is a Canker Sore?

A canker sore is a small, shallow ulcer that develops on the soft tissue inside the mouth. Common locations include the inner lips and cheeks, tongue, base of the gums, and soft palate.

A typical canker sore has:

• A round or oval shape
• A white, gray, or yellow center
• A red border
• Localized pain or tenderness
• Burning or tingling that may occur before the ulcer appears

Canker sores can make eating, drinking, brushing, and talking uncomfortable. Mayo Clinic

The National Institute of Dental and Craniofacial Research explains that canker sores occur inside the mouth and are not contagious, which separates them from fever blisters or cold sores caused by herpes simplex virus. NIDCR

Can You Get Rid of a Canker Sore in 24 Hours?

Not reliably. A minor canker sore usually needs several days to heal and often disappears within 1–2 weeks.

What can change within 24 hours is the amount of discomfort. You may be able to make eating, drinking, brushing, and speaking easier by reducing irritation and using products that temporarily relieve pain.

A useful way to think about the first day is:

A 2026 GoodRx guide also notes that there is no overnight cure, while home and over-the-counter options may reduce pain and support healing. GoodRx

What Can Help a Canker Sore in the First 24 Hours?

Saltwater Rinse

A warm saltwater rinse is one of the simplest ways to soothe an irritated mouth.

Mayo Clinic recommends dissolving ½ teaspoon of table salt in 8 ounces of warm water. Gently rinse and spit it out rather than swallowing the solution. Mayo Clinic

The rinse can help keep the area clean while limiting additional irritation.

Do not rub dry salt directly onto the ulcer. A concentrated application can sting and irritate the tissue.

Baking Soda Rinse

A baking soda rinse is another option for reducing irritation.

Mayo Clinic recommends mixing 1 teaspoon of baking soda with ½ cup of warm water and using it as a mouth rinse. Mayo Clinic

A rinse is preferable to aggressively scrubbing or scraping the sore.

Ice or Cold Foods

Cold can temporarily numb the area and make a painful sore easier to tolerate.

You can allow a small ice chip to dissolve near the sore. Cold, soft foods such as yogurt or applesauce may also be easier to eat when the ulcer is painful. Mayo Clinic

Cold does not make the ulcer disappear in one day. Its main role is short-term comfort.

Milk of Magnesia

A small amount of milk of magnesia may be used as a topical soothing option for a canker sore.

Cleveland Clinic and Mayo Clinic both list milk of magnesia among measures that may help with canker sore discomfort. Cleveland Clinic

Use the product according to its labeling and avoid swallowing unnecessary amounts.

Honey

Honey has been studied as a supportive option for recurrent aphthous ulcers. GoodRx cites a clinical study in which people applying honey to canker sores several times daily experienced less pain, redness, and swelling. GoodRx

Honey should not be viewed as a guaranteed one-day cure. The available evidence is more useful for symptom relief and possible support of healing.

Over-the-Counter Numbing Products

If pain is the main problem, an oral product containing a topical anesthetic such as benzocaine can temporarily numb the sore.

The American Dental Association lists accepted oral products containing benzocaine for temporary relief of mouth-sore discomfort. ADA

Follow the product label carefully. Benzocaine products have important age restrictions and safety warnings. The FDA advises that benzocaine should not be used for teething in children younger than 2 years because of the risk of methemoglobinemia. U.S. Food and Drug Administration

Hydrogen Peroxide Products

Some oral products containing hydrogen peroxide are used for mouth-sore care. Mayo Clinic lists hydrogen peroxide among topical ingredients found in products for canker sores. Mayo Clinic

If using a commercial mouth-sore product, follow its directions. Do not swallow hydrogen peroxide or use concentrated peroxide directly on the ulcer. Excessive use can irritate oral tissue.

What Should You Avoid During the First 24 Hours?

Reducing repeated irritation can make the sore much easier to manage.

Avoid:

• Spicy foods
• Citrus fruits and other acidic foods
• Salty foods if they cause burning
• Chips, crackers, toast, and other sharp foods
• Alcohol-containing mouthwashes
• Scrubbing the ulcer
• Picking at the sore
• Trying to pop the sore
• Toothbrushing with excessive pressure around the affected area

The National Institute of Dental and Craniofacial Research recommends avoiding spicy or abrasive foods during a canker sore flare and notes that alcohol-containing mouthwashes may irritate the area. NIDCR

Mayo Clinic also recommends avoiding rough, acidic, or spicy foods while the ulcer heals. Mayo Clinic

Canker Sore vs Cold Sore: Are They the Same?

No. This distinction matters because the two conditions have different causes and require different care.

NIDCR describes canker sores as white or yellow sores with a red border inside the mouth, while fever blisters usually appear as groups of fluid-filled blisters around the lips and are contagious. NIDCR

A sore on the outside edge of the lip should not automatically be called a canker sore.

What Causes Canker Sores?

There is no single confirmed cause. Several triggers and health factors have been associated with canker sores.

Minor Mouth Injury

A cheek bite, aggressive toothbrushing, dental work, or irritation from dental appliances can injure the mouth tissue and precede a canker sore.

Stress

Emotional stress is a commonly reported trigger. Some people notice outbreaks during periods of poor sleep, work pressure, or emotional strain. Mayo Clinic

If anxiety or stress is also affecting your health, Manhattan Medical Arts has information about anxiety and its physical symptoms.

Nutritional Deficiencies

Low levels of vitamin B12, folate, iron, or zinc have been associated with recurrent canker sores. Mayo Clinic

Iron deficiency can also cause low hemoglobin and symptoms such as fatigue, dizziness, shortness of breath, and cold hands or feet. If recurrent mouth sores occur alongside these symptoms, low hemoglobin and anemia may be part of a broader medical evaluation.

Certain Foods

Some people notice outbreaks or increased pain after eating acidic, spicy, salty, or other foods that irritate the mouth. Reported triggers vary from person to person. Mayo Clinic

Toothpaste Ingredients

Some people may develop or experience more frequent sores when using toothpaste containing sodium lauryl sulfate, also called SLS. Mayo Clinic

Hormonal Changes

Hormonal changes around menstruation have been associated with recurrent canker sores in some people. Mayo Clinic

Medical Conditions

Frequent or unusually severe mouth ulcers can sometimes occur alongside conditions such as celiac disease, Crohn’s disease, ulcerative colitis, Behçet disease, or immune-system disorders. Mayo Clinic

If recurrent mouth ulcers occur with digestive symptoms, celiac disease or Crohn’s disease may need consideration.

People with weakened immune systems, including those living with HIV, may also experience recurrent or severe oral ulcers. Mayo Clinic Manhattan Medical Arts also provides information about HIV/AIDS and related health concerns.

How Long Does a Canker Sore Take to Heal?

Most minor canker sores heal within 1–2 weeks without medical care. Pain may start improving before the ulcer completely disappears. Mayo Clinic

The type of canker sore can affect the timeline:

• Minor canker sores: Usually heal within 1–2 weeks and do not leave scars.
• Major canker sores: Are larger and deeper and may take up to six weeks to heal.
• Herpetiform canker sores: Consist of many tiny ulcers that can occur in clusters and usually heal within 1–2 weeks.

Despite the name, herpetiform canker sores are not caused by herpes. Mayo Clinic

Can Medical Care Make a Canker Sore Heal Faster?

Yes, medical care may be useful when the ulcer is severe, recurrent, unusually large, or interfering with eating and drinking.

A clinician may consider:

• Prescription corticosteroid preparations
• Prescription mouth rinses
• Topical anesthetics
• Other oral medications for severe cases
• Nutritional supplements when testing identifies a deficiency
• Management of an underlying medical condition

Mayo Clinic and Cleveland Clinic list corticosteroid preparations, prescription rinses, topical products, and nutritional supplements among options used for more severe or persistent canker sores. Mayo Clinic

Research on recurrent aphthous stomatitis also supports topical corticosteroids as an important medical option for symptom control and healing. PubMed

Laser therapy may be considered for some severe ulcers. Evidence reviews have found that laser therapy and several topical approaches can help with short-term symptoms, though results vary between therapies and studies. PubMed

How Are Canker Sores Diagnosed?

A typical canker sore can often be identified from its appearance, location, symptoms, and medical history. There is usually no specific test needed for an uncomplicated ulcer. Mayo Clinic

Testing may become relevant when sores:

• Keep returning
• Are unusually large
• Last longer than expected
• Occur with fever or other symptoms
• Interfere with eating or drinking
• Appear alongside digestive symptoms
• Occur in someone with a weakened immune system

Depending on the clinical picture, a healthcare professional may consider blood tests for nutritional deficiencies or other health conditions.

A persistent or unusual lesion may also need a closer oral examination to make sure it is not another type of mouth lesion.

When Should You See a Doctor or Dentist?

Most small canker sores do not require a medical visit. An evaluation becomes more appropriate when the sore does not follow the usual healing pattern.

See a healthcare professional if:

• The sore lasts two weeks or longer
• It is unusually large
• Pain is difficult to control
• You cannot eat or drink comfortably
• New sores keep appearing before older ones heal
• You have frequent outbreaks
• You have a fever with mouth ulcers
• Sores extend onto the outer lips
• You have other unexplained symptoms

Mayo Clinic and Cleveland Clinic both advise medical evaluation for persistent, recurrent, unusually large, or severe sores and for ulcers that interfere with eating or drinking. Mayo Clinic

For a straightforward oral lesion, a dentist may be the most direct professional to evaluate the mouth. A primary care physician can also be useful when recurrent canker sores occur alongside fatigue, digestive symptoms, nutritional concerns, immune-system problems, or other symptoms outside the mouth.

How Manhattan Medical Arts Can Help

A recurring canker sore is not always just an isolated mouth problem. When ulcers keep returning, the medical question becomes why they keep happening.

At Manhattan Medical Arts, Dr. Syra Hanif, M.D., a board-certified primary care physician, can evaluate recurrent symptoms in relation to your medical history, medications, nutrition, and other health concerns.

The evaluation may include a physical examination and laboratory testing when the symptoms suggest an underlying issue such as anemia, nutritional deficiency, thyroid disease, digestive disease, or another medical condition.

Dr. Syra Hanif’s physician profile is available through her Manhattan Medical Arts medical profile.

Frequently Asked Questions

Final Takeaway

A canker sore cannot reliably be eliminated in 24 hours. The realistic goal is to reduce pain, protect the ulcer, and limit further irritation during the first day.

Saltwater or baking soda rinses, ice, cold soft foods, milk of magnesia, selected over-the-counter oral products, and avoiding acidic, spicy, salty, and rough foods can make the sore easier to manage. Mayo Clinic

If the sore keeps returning, lasts longer than two weeks, becomes unusually large or painful, or occurs with other symptoms, the focus should shift from short-term relief to finding the reason for the recurring ulcers.

Disclaimer
This blog is for informational & educational purposes only and does not intend to substitute any professional medical advice or consultation. For any health-related concerns, please consult with your physician, or call 911.