Friend’s boyfriend pisses all over toilet seat

Me and my friend live in a house together, her boyfriend came to visit her for a few days but I discovered that when he pees, he leaves it all over the toilet seat and he doesn’t clean it. It is absolutely disgusting and it has been going on for the time he has stayed with us. How can I tell my friend that her boyfriend should clean his piss from the toilet seat cause I am genuinely about to throw up. Please somebody help me!!