It works great, but my regular doctor refused to prescribe it for the mouth, saying there is a possible link to cancer. He probably assumed they were canker sores, also called aphthous ulcers. Since the cause isn't known, there is little research on effective treatments. Many physicians and dentists feel that corticosteroids, such as Lidex, help. Clearly, your doctor who refused to prescribe Lidex is worried that it may have dangerous side effects.
Corticosteroids can have serious side effects if taken in high doses for prolonged periods.
Causing cancer does not seem to be one of them, though. No long-term studies have been done in animals to show that this family of drugs is carcinogenic. However, they may cause birth defects and are not recommended for pregnant women. One serious side effect that can occur is suppression of the pathways that regulate the normal production of corticosteroids in your body. Since Lidex is meant to be used on skin, if you use it in the mouth you may absorb more of it than is good.