Oh, allergies. Why do you do this to me? 
Hayfever - Rapeseed and grass in particular. Sneezing, watery eyes and itchy eyes are the worst. It comes in bouts, really - one year I'll have it really really bad and the next it won't be so bad and then the next it'll hardly be there at all! I have some prescription drugs which help a ton - I used to buy the ones from a shop but they didn't help me at all. 
Certain fruits and vegetables -  There is something in certain fruit and veg that makes my throat itch and swell like crazy. Eeek. I just try to avoid the ones that do this, or eat very little of them.
Mosquitoe bites - Itchyness, swelling, pussing for days. It's gross and drives me insane. Lots of insect repellent for me on summer nights. 
Certain metals - I don't buy any jewellery anymore that isn't silver, stainless steel or white gold.etc because some other metals make me come out in hives and itch me like mad. I don't know what ones in particular, though. 
Chlorine and sun - A weird allergy. If I swim in the pool on a sunny holiday I have to have a full shower afterwards before going back to sunbathing/sitting in the sun. I can't just rinse off. I have to get all the chlorine out of my hair and bikini because otherwise when I go back to sunbathing it will make me come up in hives/a rash wherever my clothes/hair is resting.