Dust.
Awesome. Because it's really easy to avoid that, problem solved.
I am glad I know now though, means I get to be referred to an allergy clinic who might do something other than give me steroids.
The doctor also said I might have something called hyper-IGE syndrome, has anyone ever heard of this or know anything about Immunoglobulins? (I know this is a long shot as even the doctor admitted he'd never heard of it, and had to look it up on wikipedia [:'(])