When my boy masturbates he pinches the urethra as he's coming so that it does not make a mess. This sounds very unhealthy to me, but i could be wrong. I'm curious if anyone else does this, and what kind of damage it could do? Any other info is welcome..thanks!

I can't believe it's exactly healthy. The natural flow is being blocked and the semen is being forced into the bladder or whereever it goes. Maybe if done occasionally, it won't do any harm but I can't see it as unharmful if its done all the time.

And when you say "my boy" are you referring to your son??? Or are you talking about yourself/friend/BF???

The guy i'm dating, it what i'm referring to! and thanks for your reply

This is NOT ok at all. He needs to leave that alone and let the ejaculation happen. Otherwise the ejaculation will "retrograde" meaning it'll end up where it isn't supposed to be at all, this can lead to infections and other problems. Tell him to stop doing this...if he has questions, send him here and let us help him understand.

yes, he needs to immedietly stop this..the best thing to do it let it have a natural flow...
1. it could stay in there, but slowly come out after a while, which can be quite embarressing.\
2. it could go back into his bladder which is EXTREAMLY dangerous.. this is a part of why the blatter is temporarly blocked off by a valve after ejaculation... so it all needs to come out..
3.. the "ejaculation" nerves could eventually get damaged.. which means they could get weaker. and THAT mean sooner or later he wont have anything to pinch

If he's worried about making a mess,tell him to wrap the head in tissue paper and let it go into the tissue,but for sure stop blocking the natural flow. It will cause him problems later if he continues with his current method.