To find my allergy triggers I kept a good journal, on the advice of my allergist. I knew my internal trigger was foods, although some detergents were a problem for my skin. I wrote down in a medium size notebook the date, time, what I ate and drank and medicines. Then I wrote down reactions. My internal reactions were usually within a couple of hours, although one time I had a reaction to an albuteral inhaler 6 hours after one puff.
Alavert (loratidine) might help you without making you drowsy. It comes in generic too.
Housemouse has a good website for skin allergies. http://www.housemouse.com/sulfites.htm I'm not sure about her vitamin B12 update. It's never helped me. But run down the page to her story. It might give you some ideas on how to discover your skin irritants. Interestingly, her allergy trigger is the same as my intolerance trigger. I don't claim to have a "true" allergy, just "intolerance" since I don't get hives or trouble breathing. I get life-threatening tachycardia.