A sore inside your lip is almost always a canker sore, and most will heal on their own within one to two weeks. The good news is that several home treatments can speed healing and cut the pain significantly while you wait. If you want faster relief, the right combination of rinsing, topical products, and trigger avoidance makes a real difference.
Make Sure It’s a Canker Sore
Canker sores appear inside the mouth, usually on the inner cheeks, inner lips, or tongue. They’re typically single, round sores with a white or yellow center and a red border. They are not contagious.
Cold sores (fever blisters) are different. They show up on the outside of the mouth around the lips, look like clusters of small fluid-filled blisters, and are very contagious. The treatments below are for canker sores. If your sore is on the outer lip, blistered, or tingling before it appeared, you’re likely dealing with a cold sore, which requires antiviral treatment instead.
Salt Water Rinse
A salt water rinse is the simplest and most effective first step. Mix 1 teaspoon of salt into 8 ounces of warm water until fully dissolved. Swish it around your mouth for 15 to 30 seconds, then spit it out. You can do this up to four times a day, plus after meals. If the solution stings too much, drop to half a teaspoon of salt. Salt water helps draw fluid out of the sore, reduces bacteria in the area, and creates a cleaner environment for healing.
OTC Numbing Gels and Ointments
Benzocaine gels (sold as Orajel and similar brands) numb the sore on contact and make eating and talking much more tolerable. Apply a small amount directly to the sore up to four times a day. Don’t use benzocaine products for more than two consecutive days without checking with a dentist or doctor, and avoid them entirely for children under two.
For a non-numbing option, dab a small amount of milk of magnesia directly onto the canker sore a few times a day. It coats the surface and helps neutralize the acidic environment around the ulcer.
Honey
Plain honey applied directly to a canker sore is surprisingly effective. In a clinical trial, patients who applied honey to their ulcers healed in an average of about 2.7 days, compared to roughly 7 days for those using a standard oral paste alone. Dab a small amount of raw honey onto the sore a few times daily, especially after meals and before bed. It stings briefly on contact but creates a protective barrier and has natural antibacterial properties.
Alum Powder
Alum powder, the astringent spice found in most grocery store spice aisles, has a long history as a canker sore remedy. It works by drying out the sore tissue. Wet the tip of your finger, dip it in a small amount of alum, and press it onto the sore for about 10 minutes. You can repeat this three times a day. Rinse your mouth afterward. Alum has been used in traditional medicine for oral ulcers without significant side effects, and research supports its use for reducing ulcer size and pain.
What Triggers Canker Sores
Knowing why the sore appeared helps prevent the next one. Common triggers include biting your lip accidentally, sharp edges on braces or dental work, acidic foods like citrus and tomatoes, and stress. But one of the most controllable triggers is your toothpaste.
Sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, is strongly linked to canker sore recurrence. A systematic review of clinical trials found that switching to an SLS-free toothpaste significantly reduced the number of ulcers, the duration of each ulcer, the number of episodes, and overall pain. If you get canker sores regularly, switching toothpaste is one of the highest-impact changes you can make. Brands like Sensodyne, Biotene, and some versions of Tom’s of Maine are SLS-free.
Nutrient Deficiencies and Recurring Sores
If canker sores keep coming back, your diet may be part of the problem. People with recurrent canker sores have significantly lower intake of vitamin B12 and folate compared to people who rarely get them. Research shows that correcting these deficiencies through diet or supplements leads to improvement in both the frequency and severity of outbreaks. Foods rich in B12 include meat, fish, eggs, and dairy. Folate is found in leafy greens, beans, and fortified grains. If you’re vegetarian or vegan, a B12 supplement is worth considering.
Iron deficiency is another common factor. If your sores are frequent and you also feel fatigued or notice brittle nails, a blood test for iron and B12 levels can help identify the root cause.
Professional Treatment Options
Most canker sores don’t need professional treatment, but for large or unusually painful ones, a dentist can apply silver nitrate to the sore. This chemical cauterization essentially seals the nerve endings on the ulcer surface, providing rapid pain relief. The sore itself may still take several days to fully close, but the pain drops dramatically after the procedure. Dentists have used silver nitrate for this purpose for decades because of its disinfecting and tissue-drying properties.
For severe or frequently recurring canker sores, a healthcare provider may prescribe a stronger topical treatment or investigate underlying conditions like celiac disease or immune disorders that can cause chronic mouth ulcers.
When a Mouth Sore Needs Attention
Most canker sores resolve within 7 to 14 days. If a sore inside your lip lasts longer than three weeks, schedule an appointment with your healthcare provider. A sore that won’t heal could indicate something beyond a typical canker sore, and your provider may want to examine or biopsy it. The same applies to sores that are unusually large (bigger than a pencil eraser), come with high fever, or make it impossible to drink fluids.