Canker sores: When your mouth speaks about your health

It often starts with something small, a sting when you brush your teeth, a sharp twinge as food touches a tiny white spot inside your mouth, or a feeling that your tongue is slightly too large for your teeth to contain.

Within a day or two, that tender patch turns into a sore that makes every sip of water or bite of food feel like fire. For many people, these mouth ulcers come and go quietly, healing within a week or two. For others, the sores keep returning, leaving them wondering if their bodies are trying to say something more.

Canker sores, known medically as aphthous ulcers, are among the most common oral conditions worldwide. According to the National Institute of Dental and Craniofacial Research, about one in four people will experience them at some point.

These small, painful lesions form on the soft tissues of the mouth, such as the tongue, lips, gums or inner cheeks. Unlike cold sores, they are not contagious. Dr Mudaki Musa, a dentist, explains that these ulcers often begin subtly.

“They usually start with a tingling or burning sensation before the white or yellow spot appears, surrounded by a red border,” he says.

Experts describe three main types. Minor ulcers are the most common, small in size and usually heal within a week or two. Major ulcers are deeper and can leave scars, while herpetiform ulcers appear as clusters of tiny sores that merge into larger patches.

Though harmless in most cases, recurrent sores can interfere with eating, speaking and overall comfort, and may point to underlying health issues that require attention.

While science has yet to pinpoint a single cause, dentists agree that several factors often overlap. Physical trauma is a common trigger, such as biting your tongue, brushing too hard, or irritation from braces and poorly fitting dental appliances. “Even something as simple as a sharp tooth edge or a rough filling can create a repeated sore at the same spot,” says Dr Musa.

Stress, hormonal changes, and deficiencies in nutrients, such as iron, folate, vitamin B12 and zinc have also been linked to frequent mouth ulcers.

Studies published in the Journal of Clinical and Aesthetic Dermatology show that nutritional deficiencies can interfere with the body’s ability to repair mucosal tissue, leaving it prone to small injuries.

In Kenya, oral health awareness remains relatively low despite rising cases of dental and soft-tissue problems. The Kenya National Oral Health Survey reports that more than 90 per cent of adults show signs of gum disease and nearly half of school-age children suffer tooth decay.

Yet many Kenyans still view mouth ulcers as harmless irritations to be ignored until they heal. “People come in only when the pain becomes unbearable. By then, some have ulcers caused by trauma from fillings or braces that could have been adjusted earlier,” Dr Musa notes. 

Canker sores can affect anyone, but young adults and women tend to experience them more often. Genetics also play a role; if a parent is prone to recurrent ulcers, their children are more likely to develop them too.

Globally, researchers estimate that between 20 and 40 per cent of people will experience aphthous ulcers in their lifetime, with women slightly more affected due to hormonal fluctuations.

Certain habits can also worsen the condition. Smoking, for instance, temporarily thickens the mouth’s lining, and some people report a spike in sores after quitting as the mucosa adjusts.

Then there is the tongue itself, often overlooked yet one of the body’s most expressive indicators of health. Some people notice that their tongue feels unusually large or caught between their teeth, causing soreness along the sides.

According to the American Association of Orthodontists, bite-alignment issues may cause the tongue to rub repeatedly against the teeth or inner cheeks, rather than the tongue itself being the problem.

The pain of canker sores may seem minor, but its impact can be far-reaching. Eating becomes uncomfortable, speech may be affected, and persistent pain can disrupt daily life. Recurrent ulcers can also signal wider health problems.

The World Health Organisation warns that persistent or non-healing oral ulcers may point to conditions such as anaemia, Crohn’s disease, coeliac disease, Behçet’s syndrome or, in rare cases, oral cancer.

Dr Mudaki Musa advises patients not to ignore ulcers lasting longer than two to three weeks or recurring in the same area. “Your mouth is part of your overall health. It reflects what is going on in the rest of your body,” he says.

Most sores heal naturally within a week or two. Over-the-counter gels or mouth rinses containing benzocaine or chlorhexidine can ease pain and speed recovery. For more stubborn ulcers, dentists may prescribe corticosteroid pastes or recommend nutritional supplements. Patients with braces or dental appliances are often advised to use wax coatings to reduce friction. “Even small adjustments, like switching to toothpaste without sodium lauryl sulphate or smoothing a rough tooth edge, can make a huge difference,” notes Dr Musa.

Diet also plays a key role in prevention. Soft, non-acidic foods and adequate hydration support healing. Managing stress is equally important, as psychological strain can weaken immune defences and make ulcers more likely.

Kenya’s growing oral health burden has raised concern among dental professionals. A BMC Oral Health study found that oral lesions, including ulcers, are common among children and adolescents living with HIV, with around seven per cent affected. Experts say this highlights the need for wider oral health education and access to regular dental care. 

Prevention begins with awareness. Regular dental visits, gentle brushing with a soft toothbrush and avoiding harsh toothpaste ingredients all help reduce irritation. People who grind their teeth or have alignment issues should seek dental advice to prevent constant tongue friction.