My wife has demographism / solar urticaria. 

DS2 has highly twitchy skin, uticaria, etc.

We have two things happen with spts - either we cannot get anything to react (including histamine) or it goes insane.  I swear our doctor does the testing anyway for poos and giggles.  He tends to base true results off the blood test.

Is that where your skin develops welts from pressure and you can write on your skin? If so, I've been diagnosed with it and my skin tests remain pretty accurate with a few false positives. My controls remain as they should be. I will have to ask my allergist along with all the questions I've been saving up.

I can't do skin allergy testing unless it's the dead of winter.  Otherwise I just react to everything, including the negative control.  So lowering my allergen load is essential if I want skin testing.  I don't really have any need for skin testing at this point in my life, though, so it's a non-issue.

Yes, me-- which is why I haven't bothered with SPT for shellfish.   Sure, it'd be positive.  And probably 50-50 odds that so would the negative control and everything else, too.

Not dx but I seem to get something like this when my allergy load is high and I forget my daily meds.

Is anyone else in this unfortunate category of diagnosed dermatrographic urticaria? Ideally in regard to SPTs.