### Human:\nmy 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's extremely stressed. it's white/yellow with a red ring around it but it's not uniform on the edges. his lip was swollen for a day but it's since subsided and clearly is inside the lip. could it be a cold sore/herpes and not a canker sore? he's never had a cold sore and says the mouth sores run in his family.\n\n### Assistant: canker sores (aphthous ulcers) are quite common and do tend to be on the inside or mucous membrane of the mouth gums or tongue. they tend to be more-or-less isolated. herpes simplex (cold sores) inside the mouth tends to be multiple cluster-like lesions. herpetic lesions can also be on the outside of the lips. canker sores do not happen on the outside of the lips.