Many of the trials are nationwide. This trial will study thalidomide for the treatment of aphthous ulcers.
Aphthous ulcers are mouth ulcers with no known cause.
Participants will be given one of three doses of thalidomide for 28 days. Those participants whose ulcers respond to treatment will then be randomly placed in one of two groups for the rest of the study. One group will take 100mg of thalidomide a day to see if it stops the ulcers coming back. The second group will take a placebo or dummy pill. This part of the study is called the maintenance phase, and will last for up to one year.