Yes he can. Actually, he would be ingesting many sperm cells, as well as the rest of the fluid which is collectively known as semen. You have to think about it. If billions of women have given oral sex over the ages, and they have ingested semen without getting sick, then why wouldn't the same be true for men who ingest semen, and especially their own which won't give them any diseases they don't already have?
Nothing happens when a man ingests his own semen.
If you are female you don't have sperm. Only males have sperm.
their own sperm
No
It's perfectly normal and safe to eat it, but if it's not your own, you can get an STD
swallowing sperm is harm less
no, only with sperm from a man
Yes, those that have flagella. For example sperm.
their own sperm
If both men are healthy with no diseases, it's safe.
no don't even try.
There is nothing that will happen if your own sperm comes in contact with a cut on your body.