Can dimetapp be used as a home remedy for canker sores?

As a Rinse: All antihistamines have some level of topical anesthetic properties. So swishing with dimetapp can sooth the canker sore pain.

Haven't heard this: I have not heard of this. My opinion is the least you do to a canker sore the better. The only real cure is time or cauterization with a laser or chemicals at a dental office. Avoid acidic food/drinks, do not aggravate the ulcer with chemicals, and rinse with warm salt water several times a day.