I do have an allergy to mangos, pumpkin and eggplant skin. The first causes numbness and tingling in mouth and lips, and a contact rash, which I discovered when a tree in the backyard of a house we were renting short term was flowering and putting out pollen. Not a good idea to walk around barefoot on the patio. I've learned the hard way to ask if a restaurant has a special house dressing or a secret sauce, and I don't drink smoothies unless I know exactly what they are made from because mangos are in a lot of frozen fruit mixtures here in Florida. Interestingly, there is 1 variety that doesn't cause the reaction, honey mango. Not sure why, but I can eat those. I very rarely eat pumpkin and actually haven't in years, but I had to stop carving pumpkins, the fancy ones, which we used to enjoy doing for Halloween because of the rash I would get from touching the flesh. My daughter also has this. Eggplant, let's just say the results of eating eggplant skin are neither comfortable or pleasant. I never order eggplant out because of that. I usually make Craig peel them because they make me itch horribly even if I wash my hands as soon as I'm done.
I used to know an older gentleman who was allergic to black pepper. Now, most of you are probably thinking he just didn't like it. Nope, his new lady friend thought that too and used some when cooking for him and didn't tell him. She ended up driving him to the ER. This was before EpiPens. Surpringly enough, they ended up married.
I'll agree that a lot of "allergies" are simply dislikes or fads, but please don't ever assume that because someone could die.