Amlexanox: canker sore paste, how to use it, side effects
Last updated September 7, 2026.
**Amlexanox is a prescription anti-inflammatory oral paste used on canker sores (aphthous ulcers) inside the mouth.** It calms the local inflammatory and allergic response in the lining of the mouth, which shortens healing time and eases ulcer pain when you start it early. Very little of it gets into your bloodstream, so it acts mostly where you put it. The most important point is time: if a sore is not clearly better after 10 days of use, stop and have the sore looked at, because a mouth ulcer that will not heal needs a different explanation.
What does it treat?
Amlexanox 5% oral paste is approved for the treatment of aphthous ulcers, the shallow, round or oval sores with a white or yellow center and a red rim that show up on the soft, movable tissue inside the lips and cheeks, under the tongue, or on the floor of the mouth. These are the sores most people call canker sores, and they typically sting most in the first two or three days, hurt with salty, acidic, or spicy food, and heal on their own in one to two weeks. It is used for the ordinary minor type in people with a normal immune system, and it works best when started at the first tingle or burn rather than after the ulcer is fully formed. It is not for cold sores on the outside of the lip, which are caused by herpes simplex virus and are treated with antiviral creams or pills instead. Amlexanox is sold only as a single-ingredient paste (the brand Aphthasol) and is not part of any combination product; separate over the counter options for canker sores, such as benzocaine gels or protective pastes, treat pain rather than speeding healing.
How do you take it?
Amlexanox comes as a 5% paste in a small tube. The usual adult dose is about 1/4 inch (0.5 cm) of paste squeezed onto a clean fingertip and dabbed gently onto each ulcer four times a day: after breakfast, after lunch, after dinner, and at bedtime, each time after you brush and rinse. That is four applications a day total, and there is no benefit to using more; do not apply it more often than four times daily. Start as soon as you notice the first symptoms, wash your hands right after each application, and keep the paste out of your eyes. Try not to eat or drink for a short while afterward so the paste stays on the sore. If you miss an application, use it when you remember, or skip it if your next one is nearly due, and never double up. Keep using it until the ulcer heals, then stop. If the sore has not clearly improved in pain and healing after 10 days of use, stop the paste and call your doctor or dentist. Safety and effectiveness have not been established in children, so a child should only use it if a clinician has specifically prescribed it.
Side effects to know
- Common: The most common effect is a brief stinging, burning, or sore feeling right where you applied the paste, which usually settles within a minute or two; some people also notice mild nausea or loose stools.
- Serious: Stop the paste and get medical help if you develop signs of an allergic reaction such as a spreading rash, hives, itching, or swelling of the lips, tongue, or face, or any trouble breathing or swallowing. Also stop and be seen if the ulcer gets larger, more painful, or develops thick drainage, if new sores keep appearing, or if a sore has not healed after 10 days, since a non-healing mouth ulcer needs an in-person look.
Who should not take it?
Do not use amlexanox if you have had an allergic reaction to it before. Talk to a doctor first if your mouth sores are large, keep coming back in crops, come with fever, rash, joint pain, eye irritation, or genital sores, or if you have a condition or take a medicine that lowers immunity, since those patterns point away from simple canker sores. Tell your doctor if you have inflammatory bowel disease, celiac disease, or known iron, folate, or B12 deficiency, because recurrent ulcers can be a sign of these. If you are pregnant, discuss it first: animal studies did not show harm to the fetus, but there are no adequate studies in pregnant women, so it is used in pregnancy only if clearly needed. If you are breastfeeding, tell your doctor, since it is not known whether amlexanox passes into human milk. Because absorption into the bloodstream is low, no significant drug interactions have been identified, but still list every prescription, over the counter, and herbal product you use, including other mouth rinses, gels, and pastes. There is no alcohol restriction with amlexanox itself, though alcoholic drinks and alcohol-based mouthwashes can sting an open ulcer and are worth skipping until it heals.
When is it an emergency?
Amlexanox paste is applied in tiny amounts, so a small accidental swallow is unlikely to cause harm, but if someone swallows the contents of a tube, especially a child, call Poison Control at 1-800-222-1222 right away. Call 911 for swelling of the tongue, lips, or throat, trouble breathing, tightness in the chest, fainting, or collapse, since these can mean a severe allergic reaction. Go to an emergency room or urgent care the same day if mouth pain keeps you from drinking and you are getting lightheaded or passing little urine, if you have a fever with widespread mouth sores, if sores are spreading to your eyes, skin, or genitals with peeling or blistering, or if you cannot swallow your saliva.
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Common questions
What is the maximum amount of amlexanox I can use in a day?
Use about 1/4 inch (0.5 cm) of paste per ulcer, four times a day, and no more than that. The four applications line up with after breakfast, after lunch, after dinner, and bedtime, each following brushing and rinsing. Applying it more often does not speed healing and mainly increases stinging at the site. Keep using it only until the ulcer heals, and stop at 10 days if it has not improved.
Can I drink alcohol while using amlexanox?
There is no known interaction between alcohol and amlexanox, and the paste barely enters your bloodstream. The practical problem is local: beer, wine, spirits, and alcohol-based mouthwashes burn on an open ulcer and can make the sore feel worse for a while. Most people find it more comfortable to skip both until the sore closes. If you use a mouth rinse, an alcohol-free one is easier on the tissue.
Is amlexanox safe during pregnancy or breastfeeding?
Talk to your doctor before using it. Animal studies did not show harm to the fetus, but there are no adequate, well-controlled studies in pregnant women, so the label says to use it during pregnancy only if clearly needed. It is not known whether amlexanox passes into human milk, so tell your clinician if you are nursing. Many people who are pregnant or breastfeeding manage canker sores with a protective paste, a saltwater or baking soda rinse, and avoiding acidic food instead.
Should I use it before or after eating?
After. Apply it following oral hygiene at four points in the day: after breakfast, after lunch, after dinner, and at bedtime. Try not to eat or drink for a short period afterward so the paste stays in contact with the ulcer instead of washing away. While the sore is healing, acidic foods like citrus and tomato, salty snacks, and spicy dishes will sting the most, so it helps to keep those off the sore area.
What happens if someone swallows the paste?
A small amount swallowed while it is on the ulcer is expected and not a problem. If a child or adult swallows the contents of a tube, call Poison Control at 1-800-222-1222 for advice; possible effects would be stomach upset, nausea, or loose stools rather than anything sudden. Call 911 instead if there is swelling of the lips, tongue, or throat, trouble breathing, or collapse. Store the tube out of reach of children and wash your hands right after each application.
Does amlexanox interact with my other medicines?
No significant drug interactions have been identified, largely because very little amlexanox is absorbed into the bloodstream from the mouth. Still, tell your clinician everything you take, including other oral gels, numbing products, steroid pastes, and prescription mouth rinses, so you are not layering products on the same sore. If your canker sores keep returning, mention any medicine you started recently, along with any history of bowel disease or low iron, folate, or B12, since those can drive repeat ulcers. Availability of amlexanox paste in US pharmacies is limited, so your pharmacist may need to tell you whether it can be filled.