Many people suffer from mouth ulcers and dentists just recommend to stay clear of products such as Bonjela and Igloo as they say they do no good and are a waste of money.
My daughter recently had the most horrendous ulcer (2 in fact, merged into one!) which was 2CM IN LENTH AND 1 CM IN HEIGHT and protruding out of her mouth!
We went to Tesco and bought this product called ORALMEDIC £5.99.
All it is is two little cotton buds (2 treatments). You just brush your teeth first, dry the ulcer completely with a clean cotton bud and then snap the end of the one from the pack and the medicine drains down to the other end of the cotton bud and goes purple. All you do is dab it on to cover the ulcer completely, leave for 10 seconds (it will sting!) and then rise with water. Job done.
Bearing in mind the huge size of my daughter's ulcer, they have now both gone in 3 days, so I suggest giving it a go! It is a little pricey I suppose, but it was SO worth the money!