You may want to try keeping a log of every chemical that could be coming into contact with your body, along with a food journal of what you eat and when.
I'm talking down to the level of which detergent you use to wash with, soaps and body creams, even fabrics etc. Maybe try different brands to see if there is any chemical sensitivities or allergies you may have. I'm going to take a guess that if you saw an allergist and they did some skin sensitivity tests, that you'd be sensitive to a lot of different substances. Trying to correlate so many variables to see if any might be causing or contributing to your problem is difficult, but, you may find some clues to help doctors narrow down some symptoms. Also, food allergies, (there are some gluten sensitive blood tests now etc.)
Good Luck!