​When you have a mouth ulcer (sometimes known as a canker sore), all the pain receptors connected to your brain seem to zero in on that one spot. Everything it encounters – food, drinks, even your tongue or teeth – hurts you like your worst enemy.

That’s because the inside of your mouth is very sensitive, and an ulcer is essentially an opening that exposes the nerves underneath the mucosa lining. Add to that the constant acid bath in your mouth, courtesy of your saliva, and you’ll understand why it burns.

If you’re dealing with one or two in your mouth right now (first, stop agitating it with your tongue!), you might be wondering: Why are you prone to these painful ulcers? More worryingly, can they be signs of something more serious, such as tongue cancer? Grab an ice cream to soothe the pain and read on to find out from the experts.


Most mouth ulcers are round or oval, and have a white or yellow centre with a red border. One of their most common causes is trauma, said Dr Chelsia Sim, a senior consultant with National Dental Centre Singapore’s Department of Oral and Maxillofacial Surgery.

They could develop from the slipping of your toothbrush while brushing, or the accidental biting of your tongue, lip or the inside of your cheeks

 “These ulcers usually develop at sites where trauma is common such as the tongue, lower lip, the inside of the cheeks as well as the floor of the mouth,” she said. “Oral ulcers can also develop on the soft palate or at the back of the throat as well as on the gums.”

The painful sores can also result from eating hot, rough or sharp foods, or using ill-fitting dentures, said Dr Aryana Rai Sia Su Ann, a dental surgeon with Raffles Dental. Virus-led diseases such as hand, foot and mouth disease, and chicken pox can be likely causes of mouth ulcers, too.


Twenty per cent of the population is believed to suffer from recurring mouth ulcers. If you’re one of them, you may have recurrent aphthous stomatitis (RAS), which causes your body to repeatedly form benign and non-contagious mouth ulcers.

You typically can tell when an ulcer is emerging from a tingling or burning sensation a day or two before it appears, according to Mayo Clinic’s website. The good news is, the severity and frequency of RAS tend to decrease with age.

The cause for RAS is not completely understood but it is believed to be “an immune system issue that causes the white blood cells to temporarily attack the epithelial cells lining the oral mucosa”, said Dr Sim. Some factors that may trigger this response include nutritional deficiencies (involving folate, iron and Vitamin B12) and allergic reactions to toothpaste, mouthwash and tooth-whitening products.

Yes, the oral hygiene products you're using could be a potential cause of mouth ulcers, especially if they contain the foaming agent sodium lauryl sulfate (SLS). A study showed that SLS could strip away the protective lining of the mouth.

“Others who have underlying medical conditions like Crohn's disease, autoimmune dermatologic conditions like lichen planus or pemphigus can also have recurring mouth ulcers. In such cases, the treatment of their underlying medical conditions will lead to the healing of the mouth ulcers,” said Dr Sim.


Three words: Topical anaesthetic gel – which you may know better specifically as the Bonjela brand. “Such gels help to soothe the discomfort but note that they do not promote healing as they do not have anti-inflammatory actions,” said Dr Sim. Whatever you do, avoid over-the-counter mouth rinses as they may aggravate and cause more pain instead, she said.

But steer clear of Bonjela if you are allergic to aspirin. The gel contains choline salicylate as one of its active ingredients – and its action is similar to that of aspirin, which is to block the body’s production of prostaglandins that lead to pain, swelling and inflammation.

Naturally, avoid hot foods that can burn as well as hard or rough ones that can scratch the mouth, said Dr Sia. These ulcers are good reason to have an ice cream, yoghurt or chilled fruits and vegetables, said Dr Sim.

What about the much-touted and painful home remedy of rubbing salt into the ulcer? A 7 per cent concentrate of table salt (sodium chloride) was found to increase the effectiveness of wound healing in a study, cited Dr Sim, which could be indicative of salt's role in healing mouth ulcers.

If you're keen to give salt a try, Dr Sia doesn’t advise using a rubbing action. “This practice may potentially cause more pain than relief by further traumatising the ulcer.” Instead, gargle with warm salt water whenever there is an outbreak of mouth ulcers to “neutralise the oral environment” and promote the ulcers’ healing, said Dr Sim.


You may have to put up with the pain in your mouth for about 10 to 14 days before they heal on their own, said Dr Sim,

However, “ulcers persisting for more than three weeks may potentially be cancerous and visiting a dentist for investigation is advised”, said Dr Sia. “Similarly, white patches that cannot be removed and persist for over three weeks should be investigated with your dental professional.”

As a quick checklist, said Dr Sim, the signs of oral cancer can include, but are not limited to, persistent mouth ulcers at the floor or back of the mouth, or under or at the side of the tongue. “The ulcer is usually painless, unless it is secondarily traumatised,” she said. “There are also red and white mucosal changes associated with the ulcer.”

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