Weedwhacker said: Sounds like an old age thing to me, RpR . 
(I've had some blood spots that look like flat blood blisters on my arms, from hitting them against some rough wood at the entrance of my hoop house, but maybe something entirely different from yours - I've never had them open up and start bleeding.)
Oh they are blood blister; today I rammed my are against a rough surface while carrying some thing and the skin ripped of two of them and out came blood.
Thankfully they are several days old and there was no blood gusher , just enough to leave a streak on the wall, and now I have to peel the skin off and put a large bandage on
.
At least I now know where they come from; as I get older , my allergies seem to be more aggresive rather than going away.
