Question of running and strange blisters.

One for the runners among you, if you please. I'm just back from the gym where I had a swim and then ran a fast-for me Miss Finn so don't laugh- 5k in 27 minutes. I got off the threadmil and felt fine, did some stretching and wandered down stairs to the showers. I was very red faced- natural for me, I pinkify very easily when working out- and was most happy to get under a cool shower But hullo, I noticed as I was getting out that I felt a bit faint and as I was getting dressed I saw tiny blisters, like droplets of water, on both my shins and where the strap of my over the shoulderboulderholder sports bra was.
Doe anybody have any clue what this means? Has anyone experienced this before? Could it just be from over heating?
Yours, in minor confusion,
FMC