Semen directly on lips would be a theoretical risk only. Note that Dr. Hook said he did not recommend testing for the event mentioned. This situation is a non-event, as the fluid was on the person's hands first. HIV is never transmitted via one body part, to another, and then another. You have zero risk for HIV infection here.
https://
www.medhelp.org/posts/HIV---Prevention/question/show/575332
This is the only reason I’m concern. The dr said it’s a risk.