My 10 year old daughter (in my sig) has Crohn's and Colitis and she has had mouth ulcers on and off since she was 18 mos old. Mouth ulcers are fairly common with Crohn's. If you call your doctor, they will probably give you a prescription or advise you of what to use. I know some people use salt water, but we've always used the prescription meds (they don't sting). Good luck