I think I might know what you're talking about, though I don't have a name for them. I've gotten them, too, mostly on my lower lip. In 20 years I've probably only had a few that have gotten big (by big I mean pea-sized, maybe slightly larger). I've had several smaller ones (b-b size) that go come and go on their own. They look just like a blister - clear raised area filled with clear fluid. I've popped one or two with a needle and it's just like popping a blister.
One, when I was a teenager (20 years ago), wouldn't go away, and it got as big as a peanut on my lower lip, so I had to have an oral surgeon remove it. He just gave me local anesthetic, cut it open with a scalpel, drained the fluid, and then stitched it back together with a couple stitches on my lower lip.
He said that what they are is this: There are tons of mucuous membranes lining the mouth and lip area, and those secret mucus, somewhat like pores secreting oil on the face. Sometimes those mucus membranes get blocked and then a blister-like sac forms and contains the mucus, which is generally clear and watery. The blockage could occur from all sorts of things, including hitting the lip with a toothbrush, chewing on food, and other minor physical injuries. For whatever reason, the doc said some people are just a little more prone to have these occur.
I don't think they're anything allergic or Crohn's related, and I think they're mostly a cosmetic concern and not a real medical concern.