They've just appeared yesterday, they're quite similar to athlete's foot type blisters I've had before but they're on my back. They're raised, red, hard to the touch, blister like, shiny, they dont itch but if I touch them they feel jaggy! There's about 5 of them, a couple on their own and the others clumped together, and they're about the size of the average mole/freckle (about 3mm diameter). What are they?