I've never been particularly allergic - no hay fever, asthma, food allergies etc - but I did have a nasty experience with perfume a few years back. Back then I really got into perfumes and used to hang out on a forum callled Basenotes where people would discuss perfumes old and new and swap samples. Never had a problem with any of them until a lady who was an artisan perfumer offered up some samples to try. I usually apply by spraying down the inside of each forearm and down my chest, and I spritzed liberally. First day was no problem but I tried a different sample each day for several days and suddenly I got the mother of all rashes. I had to get some prescription strength steroid cream from the doctor in order to shift it. It was extremely itchy and uncomfortable. I don't know what she used - she claims it was all natural - but I was definitely allergic to one of the ingredients in her perfumes.
The only other thing that really bothers me is chlorine. I had a foot operation over summer and couldn't do much in the way of walking so decided to swim instead. I've had the sneezes after swimming before but it steadily got worse after each swim until last Sunday when I couldn't breathe through my nose for a whole night. I remember swimming around 15 years ago with no problems so it may just be the amount of chlorine they use at the local pool due to it being public and used by kids.