Your description of the blisters leaking fluid once stabbed reminds me of my own periodic (though thankfully minor) skin condition pompholyx (http://dermnetnz.org/dermatitis/pompholyx.html). Triggered by stress, looks like little bubbles beneath the skin, often itchy and only spreads once the little bubbles have been burst. Fortunately mine's so minor that I never needed to see a dermatologist: I just only have to refrain from bursting the bubbles for the complaint eventually to give up and go away.

Do you suffer from asthma, ezcema or hay fever? The three are interlinked and proneness to one or more of these might make you prone to pompholyx.