So close...

Jacob has a rash behind his knee that's irritating him. When I was putting him to bed he had a request for me in such a pitiful voice:

Jacob: Mom? You know the spot behind my knee?

Mom: Yes.

Jacob: It's hurting me. Can I put some gasoline on it?

Mom and David (one of his roommates): Gasoline!?!

Jacob [giggling]: Not gasoline - Vaseline!

Similar names - not similar products...