Food allergies are serious -- even the mild ones. If you've been experiencing mild to moderate allergy symptoms that seem to be linked to food, your doctor will want you to undergo allergy testing to find out exactly what is causing your problems. Most of the time, a skin test or blood test can give you this information, but there are times when an elimination diet is the best test. It's also good practice for dealing with food if you find out that the eliminated food is really at the root of your troubles. And if that food was one of your favorites, you need to develop some coping skills.
In the Short Term
If you're just in the testing stage right now, keep that end date in mind and do your best to avoid the food and its derivatives. Most of these tests last between a week to two weeks, which gives your body time to recover from the allergy symptoms. Of course, if the symptoms don't go away or even get better a bit, then you know that food likely wasn't the cause. But if the symptoms do go away, at the end of those weeks, you get to eat the food again to see if your symptoms come back. So there's an end in sight to the test; just keep reminding yourself of that as you power through those days.
If it does turn out that you have to eliminate that food, and it was a favorite, remember how you felt when you ate it when you get a craving for it. Remembering the rashes, stomachaches, or other symptoms can often help you overcome the urge to eat that food.
Looking for Substitutes
Don't wait for the test result to start looking for substitutes because those substitutes could help you get through the test period. But even if you start looking after the results are in, chances are you can find something that gives you the type of taste or texture that you want when you crave the food you now have to stop eating. Look in health food stores, of course, but also check out books and websites dedicated to allergy diets as well as other (sensible) diets. You don't have to follow those diets, but you could find recipes that work for you. For example, if you find you have to avoid rice (it's not a common allergy, but it is possible to become allergic to it), the cauliflower rice recipes you find on low-carb diet sites could give you a passable substitute.
External Resistance
One of the worst aspects of food allergies is encountering people who don't believe in them, or who don't believe you have one, especially if you developed one as an adult. Start rehearsing responses to claims like "A little won't hurt you" or "Aren't you exaggerating just a bit?" It's best to expect these comments and be pleasantly surprised if you don't get them. Above all, don't give in. You don't have to hurt yourself to prove a point to someone who apparently wants you to be hurt.
You'll get through the test; it won't take long. And if it turns out that you can no longer eat a favorite food, remind yourself that at least now those symptoms that made you feel so sick are now gone. Your allergist can give you more tips on coping with a food allergy.