This section will always be a work in progress. Check back from time to time for more updates! – Here’s the disclaimer: If you question whether or not these substitutions will work for you, please check with your doctor first. 😉
The bulk of my food allergies are due to grass pollen in foods. When I went for the “prick tests” the allergist told me the things I was allergic to would swell up like mosquito bites. For the most part, they did, but the spot on my back for grass swelled far beyond that, and felt like it wanted to take over my back. They actually called people in from other rooms to look at it. Awesome. (By awesome, I mean, not awesome at all.)
Grass pollen allergies are tricky because you may not always react to the same type of food twice. Also, I’ve been told by an allergist that apparently grass pollen in foods can break down from cooking. However, there is no set “magic time” to cook things to make this happen. For me, this type of allergy is usually more annoying than dangerous, but every time you are exposed to something you are allergic to, it heightens the sensitivity. If you have a food allergy, I find it is better to steer clear of it as much as you possibly can.
Bananas/Eggs
Bananas and eggs are commonly used as a binder in recipes. Try pumpkin puree as a substitute. It is similar in texture, and tastes great in recipes. Depending on your allergy, you may be able to substitute plantains for bananas. Many people who are allergic to bananas find they are not allergic plantains. Just note that plantains are usually less ripe than bananas, and may be a little harder to work with.
Butter
Try using extra light olive oil as a butter substitution. It is more mild than extra virgin, and can pass as a buttery flavor. You will need to modify the amount however. To do so, check out this chart from Filppo Berio:

Generally speaking, a fat is a fat, and many are interchangeable. If I am out of extra light olive oil, I substitute regular olive oil, canola oil, or vegetable oil. I wouldn’t recommend using grape seed oil or extra virgin oils for butter substitutes (though I love them for other things.) They have very distinct flavors, and can overpower a recipe.
Citrus
One of the main functions of adding a splash of lemon or lime juice to recipes is to make things a little tart, and to keep things (like apples and avocados) from turning brown. I’ve read that vinegar works as a citrus substitution, and though it can be great in a lot of recipes, adding vinegar can be a quick way to make something taste horrible. I typically use white wine as a substitute. I keep a boxed wine in the fridge fridge to avoid cracking open a new bottle for a tablespoon or two for cooking. (And, who am I kidding, I drink it. Boxed wines have come a long way, and with less packaging waste than bottles, they are eco-friendly. I’m just doing my part to save the planet.)
If you are substituting citrus is a pie or dessert, a variety of liquors will work as well. Here’s where trial and error will come into play, but you have a lot of “wiggle room.” For apple pies, I use apple brandy. You could also used spiced rum. In other fruit pies you can use a coordinating schnapps, or rum, or, brandy. Try different flavor combinations, and see what you like the best!
Pineapple is actually not a citrus fruit. However, it is also a common allergen, so try it with caution. I am allergic to citrus, but not to pineapple. I use pineapple juice instead of orange juice for making mimosas, or as an orange substitute in certain recipes.
Nuts
Nuts add crunch, flavor and texture to recipes. Try replacing them with plain granola, thick cut rolled oats, pumpkin seeds or sunflower seeds. I particularly like granola as a substitution in salads – I hope you will too!