EagleViewArabians wrote:
Are you sure he doesn't have Canker sores and not cold sores? Cold sores are the herpes virus and although staying healthy by increasing water intake and balancing his diet would help, I don't see how a change of toothpaste would make a difference. It's all about the immune system.

I've actually wondered if what I have in my nose is canker... but I haven't pursued finding out.