I don't take aspirin because I thought I might have that allergy. I had nasal surgery a number of years ago to remove a family of polyps; they may have been caused by an allergy to ibuprofen. Ibuprofen and aspirin both belong to the family of NSAID painkillers. Apparently there's some sort of inherited condition that predisposes a person to be allergic to NSAIDS, develop nasal polyps, and have something else happen that I've forgotten about it. It obviously runs in my family.
Hypothesis 4: Salicylates applied to the skin in a personal hygiene product.
Supporting Evidence: Detailed above.
Experiment: I crushed up a baby aspirin and mixed it with a little water to make a paste. Then I applied this to my inner arm in one of my home allergy tests.
Results: About 10-15 minutes later, after I rinsed the aspirin residue off my arm, I developed an itchy rash in that area. It went away after another 10 or 15 minutes, but for the next hour of so I had vague itchies around various parts of my body (salicylates can be absorbed by the skin and cause a systemic reaction) and my tongue felt weird.
Based on this result, I went around the house looking at labels to find anything containing "salicyl-" ingredients. Lo and behold, one of the lotions that I really liked and was using all the time contained benzyl salicylate. Also, my California Baby shampoo has willow bark extract in it. Willow is what aspirin was originally derived from.
None of my other lotions seem to be problematic, but I'm going to stick with the California Baby lotion (no willow bark) for a little while until I get another lotion. My dad says he uses Aveeno and has no problems with it.
I'm also going to keep going on the hypoallergenic diet just in case there's a food aspect as well... but the foods that contain salicylates are numerous and varied (and include most fruits and vegetables), so if I'm allergic to it in food I'm just doomed.