Can mouthwash such as listerine make ulcers in the mouth worse?

Should make it bette. Canker sores are wounds in mouth which can be helped by rinsing w antibacterial rinse such as listerine. We recommend the alcohol free version as alcohol in the rinse dries the mouth without additional antibacterial effects.
Yes. There is a high concentration of alcohol in listerine that can irritate the ulcers and make it take longer to heal.