Step one: Avoid the offending food for at least 3 months
The best way in knowing whether you have delayed–onset food allergy is by having yourself properly tested. This would eliminate all the guesswork on your part. IgE allergy testing involves state of the art blood tests to properly diagnose your food allergies. Every person is unique and should be properly tested. A person with delayed–onset allergies may be allergic to less common allergenic foods such as chili peppers, chicken, kiwi, garlic, red meat, citrus fruits, tomatoes or onion. If however there are no sophisticated blood assays in your area that would test your blood sample against more than a hundred kinds of food to determine whether you react to any of them or not, then an allergen–free diet for two weeks would help you make intelligent guesses as to what is causing your discomforts. Keep a food diary and write down all the symptoms that you'll be experiencing for the next few days. Take note of all the food that you frequently eat and see if they make you feel worse a few hours to a few days after eating them. A clue to determining your allergy to a certain food is if you strongly like a certain food and feel great satisfaction when eating it. Much like in alcoholism and chain smoking, the body creates a strong attachment and addiction to the very substance that is harming the person.

Once you’ve made your list of allergy suspects, carefully plan your diet for the next several days and eliminate all the suspect foods for two weeks. Notice how you feel when you are not consuming them. Chances are you will feel great relief within a week. Some people who suffer from edema due to gluten allergy lose a lot of retained water and therefore shed a few pounds in a couple of days without exercise.

Note that you might feel your old symptoms within the first few days of abstaining from the offending foods. This is a normal reaction and will disappear in about five days.

If you still feel bad after eliminating a number of foods from your diet, check your food diary if there is anything else that you eat often that you haven’t eliminated yet. Could it be that cup of coffee, tea, or hot chocolate? It could be an ingredient included in a lot of the items that you eat. A highly–qualified nutritionist who specializes in food allergies would greatly help by asking you the right questions. Your nutritionist can help you determine whether you’re truly allergic to something or merely sensitive or intolerant to it. But either way you would be advised to avoid the food that causes your allergy or sensitivity until you are ready to reintroduce it to your body.

After doing your elimination diet for two weeks, try reintroducing each food you’ve avoided one by one every five days. For example, if you avoided gluten, dairy, and soy, try eating food containing gluten on day one. Then completely avoid it again for the next five days. If you notice your symptoms go back within five days then you have a clear sign that you are truly allergic to it. Then you can move on to dairy and eat cheese for a day then abstain from any kind of dairy product or ingredient for the next five days and see if your symptoms recur. Do the same with soy. If you react to all three then you would have to avoid all of them in the next three to six months before you can reintroduce them in your diet.

You would also have to educate yourself with regard to food families and hidden food ingredients. You might be reacting to soy but decide to eat a product containing TVP or textured vegetable protein since it does not have the word “soy” on the label, and find your asthma symptoms coming back. You may be allergic to gluten but not to soy and may be surprised to find yourself reacting to soy sauce, which often contains gluten. This would involve a de rigueur label reading to check if a certain food contains an allergen as one of its ingredients. Eating out can also be a challenge to the food allergy sufferer. Cross–contamination is frequently what happens when the restaurant doesn’t wash utensils that would be used for the dish you ordered after preparing a food that you may be allergic to. You may ask the waiter to skip the breading in your fried fish if you have gluten allergy, but the cook may not change the oil and clean the pan where he just cooked breaded chicken. Don’t hesitate to ask the waiter the ingredients of the dish you wish to order, or to inform the chef of your allergies. As a general rule practice caution when eating out.

It takes three to six months for your body to replace all of its IgG antibodies. The new batch of IgE antibodies would have no memory of the list of foods you were strongly reacting to. Provided that you have reversed your leaky gut, the new set of IgG antibodies would have no more reason to attack the food you were previously allergic to.

After three months or so you can start reintroducing all the previously offending foods one by one, it is better to take quercetin right before reintroducing old allergens (see below). Stay away from food that promotes inflammation and mucus formation such as dairy and meat. Avoid alcohol and drink lots of water.