I have a co-worker that smells vivdly of very sour milk. What could cause this?

Luckily he sits on the other side of the office. But we had a movie night last night and he walked in and sat right next to me. Immediately, it smelled so strongly of sour milk, I can’t even describe how disgusting it was. I’d heard people complain about his odor before, but never experienced it myself. I had to leave.

Now I can’t miss it. Every time I walk near his section of the office, I literally feel sick to my stomach. I don’t know how people work near him. Apparently HR has received several complaints, and plan on doing something about it soon.

I figure it has to be a disorder or something, or the WORST hygiene possible. Does anyone have any idea what would make a person smell like very sour milk?