Can you explain what frotting is and if there are any risk factors?
I had to look this up. Frotting is rubbing two penises together for sexual pleasure. Like dry-humping. Risk factors would be transmission of STIs, especially those that live on the surface of the skin like HPV or herpes. It would technically be possible to spread other STIs like gonorrhea or chlamydia if there was exchange of semen, though this risk would be low.