Canker sore bottom of mouth

A canker sore on the floor of the mouth is a shallow ulcer in the movable lining beside or beneath the tongue, usually tender and not contagious.

It may follow minor trauma or irritation, and recurrent or persistent ulcers need assessment for other causes.

Avoid spicy, acidic or sharp foods, use a soft brush and rinse gently with salt water; do not scrape or burn the ulcer.

A dentist inspects its size, edge, colour and location, checks nearby teeth and asks about recurrence, medicines and other symptoms.

Seek care if it lasts beyond two weeks, keeps returning, enlarges, hardens, bleeds without trauma or comes with a neck lump or swallowing difficulty.