I had something similar that plagued me a couple of years ago, sounding verrry similar to what you’re describing.
My blisters, all very small as you described, showed up in clusters. Most were about the size of the periods in this message, with some occasionally as large as a small letter “o.”
They would start out clear, but darken, presumably as the result of other fluids leaking in–like blood.
It happened on my right hand only, at the tips of the the index and ring fingers, on the left side of the thumb, and the right side of the ring finger.
My dermatologist said just that it looked like some kind of irritation to the fingers was what was causing them, and gave me some creams to dry them up. But he also said that that didn’t get to the source of what was actually causing them.
I narrowed it down to two things: my mouse and some other skin creams. The places where the blisters occurred corresponded exactly to the places where my fingers dragged across the desk moving my mouse. When I bought a track-ball, they went away.
However, that also corresponds to a time when my GF was having an unrelated skin irritation of her own. When I applied the ointment in the places she couldn’t easily reach, the same areas of the fingers did the brunt of the contact. Her irritation finally ended about the same time as I bough the track-ball. I could have been allergic to the cream.
Another vote for the suspicion of the “cream allergy” theory is that is a year or so later it happened again–but this time only on the index finger. The only thing that had happened out of the ordinary was that just before those blisters showed up, I had had a cold sore outbreak, and for the first time tried Abreva to treat it. I used the index finger to apply the Abreva.
I’ve used the word “blister” pretty freely, which usually implies something large. But, as in the cases you’ve described, they were so small that they didn’t cause the skin to raise at all.
BTW, I vouch for my own results with Abreva. It shaved a good 3 or 4 days off the normal recovery time, and I never grew one of those thick, ugly scabs in the meantime.