One of my daughters has an anaphylaxis level allergy to peas (amongst not quite so severe allergies to several other foods).
Bear in mind that people with severe allergies like this can taste minute quantities of what they're allergic to, i.e. at levels that no-one else would taste. AFAIK it's a result of the allergic reaction starting in the mouth as soon as a trace of the food gets in there rather than actual tasting as such, but it amounts to the same thing, i.e. detecting the food in minute quantities right away.
This is not just going by my daughter (who's 7 and not that good at explaining stuff like that) but also adults I've talked to who have anaphylaxis, and have reported that they can taste the allergen in the food, even just a trace of it, but at that point it's too late to stop the allergic reaction. So trying to disguise the taste is not really relevant - though your MC might not know that, and the bad guy can realise right away what the MC's done and hurt him badly before the anaphylaxis gets to a level that incapacitates him. (Or, if he's not so bad, he'll use his epipen and call an ambulance for himself or ask someone to call an ambulance, which might be what you need for your plot. You can't do stuff after injecting yourself with the epipen. You have to lie down and wait for the ambulance.)
Note: this tasting thing may not apply to everyone who suffers from anaphylaxis
Also, if it's the good guys doing this to incapacitate the bad guy, giving someone an allergen when you know they have anaphylaxis is attempted murder. Or murder if they die from it, which is a distinct possibility. There's a danger your protags are going to come of looking more evil that the bad guy.
If the allergy is less severe, it won't cause swelling/restriction of airways or a drastic drop in blood pressure (associated with anaphyalxis) but can still cause some quite debilitating symptoms, such as vomiting, diarrhoea and hives (vomiting and hives shortly after ingesting it, diarrhoea tends to be more of a delayed reaction when the allergen gets to the gut) - bear in mind that antihistamines can quickly stop such a reaction - usually they work within about 5 mins. If the character has moderate or severe allergies then it's likely they'll carry medications with them.
Another thing, I'd find it a bit too convenient (in a deus ex machina kind of a way) if it just so happens that the bad guy has anaphylaxis and a reason for not carrying epipens/medication and also is stupid enough to eat food that's been prepared by someone who has a reason to want to try to incapacitate them. Having anaphylaxis makes you extremely careful about what you eat, double checking ingredients and avoiding sources of food that you can't be sure about. There are other ways to sneakily incapacitate someone. Slipping someone some medication - maybe one of the guests is a bit nosy and checked out the medicine cabinet when they went to the bathroom, then remembers seeing sleeping pills, opiate painkillers or something like that - is a possibility that doesn't require the antagonist to just so happen to have a severe allergy.
Going back to your original question - you can be allergic to anything. I had never heard of pea allergy when my daughter had her severe allergic reaction. Thankfully NHS 111 (non-emergency NHS number) knew what was going on and sent an ambulance. Some allergies are more common than others, and some that more commonly cause anaphylaxis than others. So you can choose whatever food you want, near enough. I once read a magazine article about a guy who was allergic to water (skin allergy, i.e. breaking out in hives if his skin got wet, I'm assuming he could still drink water otherwise he'd be dead.)