Most mouth sores heal on their own within two weeks, but the right care can reduce pain and speed that timeline. What you do in the first few days matters: keeping the sore clean, avoiding irritants, and using the right topical products can make the difference between a week of misery and a few uncomfortable days.
Before jumping into treatment, it helps to know which type of sore you’re dealing with, since the approach differs.
Canker Sores vs. Cold Sores
The easiest way to tell these apart is location. Canker sores form inside the mouth, on the inner cheeks, lips, or tongue. They look like single round white or yellow sores with a red border. Cold sores (fever blisters) form outside the mouth, usually around the border of the lips, and appear as clusters of small fluid-filled blisters.
The causes are different too. Cold sores come from the herpes simplex virus (usually HSV-1) and are contagious. Canker sores aren’t caused by a virus and can’t spread to other people. They may be triggered by minor injuries (like biting your cheek), stress, smoking, or nutritional deficiencies in iron, folic acid, or vitamin B12. Most of the advice below applies to canker sores, which are the more common complaint. Cold sores typically need antiviral treatment, so if you’re dealing with blisters on or around your lips, a pharmacy antiviral cream or a prescription from your doctor is the most effective route.
Saltwater and Baking Soda Rinses
A rinse is the simplest and cheapest first step. It cleans the sore, reduces bacteria around it, and can temporarily ease pain. You have two good options:
- Salt water: Dissolve half a teaspoon of salt in a cup of warm water. Swish gently for 30 seconds, then spit.
- Baking soda: Dissolve 1 teaspoon of baking soda in half a cup of warm water. Swish and spit.
The baking soda rinse neutralizes acids in the mouth that irritate the sore, while salt water draws fluid from inflamed tissue to reduce swelling. Either one works well. Rinse three to four times a day, especially after meals, to keep food particles from settling into the ulcer.
Over-the-Counter Pain Relief
If the sore is painful enough to interfere with eating or talking, a topical numbing gel can help. Products like Orajel contain 20% benzocaine, a local anesthetic that numbs the area on contact. You apply a small amount directly to the sore with a clean finger or cotton swab, and relief kicks in within a minute or two. The effect lasts about 30 minutes to an hour, so it’s most useful right before meals.
Protective pastes are another option. Some OTC products form a thin barrier over the sore, shielding it from food and saliva. This reduces pain and gives the tissue underneath a chance to heal without constant irritation. Look for products specifically labeled for mouth sores or oral ulcers at your pharmacy.
What to Eat (and What to Avoid)
What touches the sore matters as much as what you put on it. Certain foods actively slow healing by irritating exposed tissue, while softer choices let the area recover faster.
Foods that make sores worse fall into three categories:
- Acidic foods and drinks: Citrus fruits, tomatoes, pineapple, berries, vinegar, coffee, fruit juice, and alcohol. These cause a stinging or burning sensation and can delay healing.
- Spicy foods: Hot peppers, hot sauce, sriracha, curry, chili powder, cayenne, and salsa. The capsaicin in these ingredients directly irritates open sores.
- Hard or crunchy foods: Chips, pretzels, popcorn, crusty bread, granola, and crackers. These can scrape the sore and reopen healing tissue.
Stick to soft, cool, or room-temperature foods instead. Yogurt, mashed potatoes, scrambled eggs, oatmeal, smoothies, and soup (not too hot) are all easy on the mouth. Drinking through a straw can help liquids bypass the sore if it’s on your inner lip or cheek.
Nutritional Gaps That Cause Recurring Sores
If you get canker sores regularly, not just once in a while, a nutritional deficiency could be the underlying cause. Research on patients with recurrent mouth ulcers has found that iron deficiency is present in about 20% of cases, vitamin B12 deficiency in roughly 5%, and folic acid deficiency in about 3%. Zinc deficiency has also been linked to frequent outbreaks.
This doesn’t mean everyone with a mouth sore needs supplements. But if you’re getting sores every few weeks or months, it’s worth paying attention to whether your diet is low in red meat, leafy greens, legumes, eggs, or fortified cereals, which are the main dietary sources of these nutrients. A simple blood test can confirm whether a deficiency is behind the pattern, and correcting it often reduces how frequently sores return.
Prescription Options for Severe Sores
When a sore is large, extremely painful, or keeps coming back, over-the-counter options may not be enough. Doctors and dentists can prescribe stronger treatments, including medicated mouth rinses sometimes called “magic mouthwash.” These custom-mixed rinses typically combine an antihistamine to reduce swelling, a steroid to calm inflammation, and an antifungal to prevent secondary infection. You swish the liquid around your mouth and spit it out, and the combined effect can dramatically reduce pain and healing time for stubborn ulcers.
For isolated severe canker sores, prescription steroid pastes applied directly to the sore are another common approach. These work by suppressing the immune response that’s creating the inflammation, which shrinks the sore faster than it would resolve on its own.
How Long Healing Takes
A typical canker sore heals within two weeks without any treatment at all. With active care (rinses, avoiding irritants, topical products), most people notice improvement within 5 to 7 days, and many smaller sores resolve even sooner. The worst pain is usually in the first 3 to 4 days, then gradually fades as the ulcer closes.
Larger sores, roughly anything bigger than a centimeter across, can take longer and sometimes leave a scar. These major canker sores are the ones most likely to benefit from prescription treatment.
When a Mouth Sore Needs Attention
A mouth sore that hasn’t healed after three weeks is worth getting checked. The NHS lists this as one of the key warning signs for oral cancer, along with a persistent lump in the mouth, lip, neck, or throat, a red or white patch inside the mouth, unexplained difficulty swallowing or speaking, and a hoarse voice that doesn’t go away. A single canker sore that heals normally is not a cause for concern, but any sore that lingers well past the two-week mark, keeps growing, or comes with other unusual symptoms should be evaluated by a doctor or dentist, who can determine whether a biopsy is needed.