The big picture is being lost here. If he left his lips alone, but continued to use the same toothpaste his lips probably would have not healed!!! Hence, his EC was caused by an allergy. If others have an allergy to food or something else they can't pinpoint, their lips will not heal by just leaving them alone. He was lucky to find out exactly what his allergy was.
By the way, I only brushed my teeth with water for months so I don't have an allergy to my toothpaste. I have to figure out if I have an allergy to anything, but it is a hard task.