What Causes Red Pin Prick Blood Dots On Legs After Sunbathing?

I am 45 yr old female and have always sunbathed, in the past few years any little sun I get I get tiny little fluid filled blisters and they itch. Today I am getting red pin prick blood dots all over my legs and today I had full length pants on as I was trying to avoid getting sun exposure to my skin but my skin seems to still have a reaction.