Awww I feel for anyone with allergies, especially to nuts or wheat!!
My DS was sensitive/allergic to red dye from a year old to about 5. We found out the hard way when he had his first red freezie. He got a rash on his cheeks really badly. We didn't know at the time it was from red dye. Then he had a red popsicle about two weeks later and he puffed up like a blowfish!!! Rushed him to the ER and they did every single allergy test they could think of. Because it was a freezie and a popsicle, they could narrow it down to red dye. So nothing red for him until he was five and then he ate a red freezie at a party and nothing happened. Called the DR and he said to try again with a red popsicle or some red vines or anything with red dye in it. We gave him a red popsicle and nothing happened!!!
They figured his system outgrew it.
At 8, he had a bad sinus infection and they gave him Zythromax (antibiotic) and thankfully we were at the dr's office because he was covered in hives in about two minutes. Head to toe, they were everywhere!!! Dr said "Ooops..think he's allergic to this one!"
We haven't tried him with it since. Thankfully he hardly ever gets sick (he's been sick three times in 14 years!) so we dont' have to worry much.
As for me, I am allergic to caffeine in certain drinks/pills. I can eat chocolate because there isn't much in it and it's processed differently. Can't take any pills with it (codeine for one!) and I can't drink caffeinated drinks. So no Coke, Pepsi, or Coffee (which I hate anyway!) or caffeinated teas. I can drink root beer and ginger ale and drink chai tea though.
Poor her (and you!) My youngest (also 3) is allergic to milk. We have good friends whose daughter is severely allergic to tree nuts, so I know the hassle of shopping for someone with allergies, every time we had them over or parties or whatever you have to read the label on EVERYTHING. 
