 [ Symptoms ] my partner has an ulcer on the inside of his upper lip and it looks like a canker sore but could it be a cold sore  i had a canker sore inside my lower lip after biting it whilst eating two days later my boyfriend got what looks like a canker sore inside his upper lip he says he gets them when he is extremely stressed it is whiteyellow with a red ring around it but it is not uniform on the edges his lip was swollen for a day but it is since subsided and clearly is inside the lip could it be a cold soreherpes and not a canker sore he is never had a cold sore and says the mouth sores run in his family [ Disease ] yes it would be safe to use zantac with the medications your daughter is taking