My roommate only washes up if he poops, never after peeing. Now every time I’m in any of the common areas I have to wash my hands after touching anything I haven’t wiped down. Thus, I wash my hands twice every time I use the bathroom; once as normal and again in the kitchen because I touched the taps, light switch and door handle in the bathroom which likely have groin sweat on them… /rant
He really should stop being lazy and wash his hands. While feces is much more dangerous than what’s likely hanging out on his junk, there’s still plenty of transmissible nastiness that he’s leaving everywhere.
But if he’s not going to change his behavior, you can mitigate by turning off the taps and handling the bathroom doorknob with a paper tissue if you use tissues to dry your hands (although I think this is common mostly in public washrooms). The overwashing you’re doing to compensate for his underwashing is not good for your hands.
I was worried about that too but my hands are fine actually. I use lukewarm water and it appears to actually help since I haven’t had any eczema flareups on my hands for a long time.