If you’ve ever had a mouth ulcer, you’ll know how much a tiny sore can take over your day. These small, painful patches that suddenly appear inside your mouth make eating, drinking and even talking surprisingly uncomfortable.

The good news is that most heal on their own within a week or two. But understanding why they appear and what you can do to prevent them can make a big difference.

Mouth ulcers are incredibly common. Up to a quarter of the population will experience them at some point in their lives, and they’re especially frequent in teenagers and young adults. Some people get one or two a year; others find they pop up every month. They’re not contagious and they’re usually harmless, but they can still be miserable.

So why do they happen? In many cases, it’s something simple. Trauma to the area – from accidentally biting your cheek, scraping your gums with a toothbrush, or irritation from braces or dentures – can trigger an ulcer. Certain foods, especially spicy, salty or acidic ones, can also irritate the lining of your mouth. Stress, tiredness and hormonal changes play a role too, and some people notice ulcers appear around their monthly period or........

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