The Elimination Diet is very lean and very bland to anyone accustomed to the Standard American Diet. Following the ED consistently, even for only a few weeks, is a major challenge to individuals accustomed to rich, spicy foods. If you have the virtues of courage and persistence, you can follow the ED without making any exceptions whatsoever. (Making exceptions in the middle of an experiment is self-defeating.)
I have only one change to suggest for the McDougall Elimination Diet, if you have the same type of medical problems I had: Replace the brown rice with white rice or, better yet, avoid rice altogether. White rice is much less acid-producing than brown rice, according to Berardi's PRAL list, but it still is somewhat acidifying. Eat other alkaline-producing starches instead -- roots (potatoes, sweet potatoes, etc.) and gourds.
After you have followed the Elimination Diet for several weeks, making no exceptions, and if you see some improvement, then perform the standard re-introduction test: Eat at least one official serving (typically one-half to one cup) of the suspect food per meal, for six meals in a row (generally, two days); and then wait a few days for a flare-up, if any.
An example re-introduction test-food might be pinto beans. If the standard serving size is, let's say, ½ C cooked, then I would eat ½ C of beans at each meal for six meals in a row. I definitely had a flare-up each time I tested one of several kinds of bean. Beans, I concluded, were not an acceptable food. Much later I found -- from Berardi's PRAL list and from further experimenting -- that green "string" beans are acceptable, but all others are bad for me. That is probably due to the fact that green beans are more "green" than "bean."
I started each six-meal test series on Monday morning at breakfast, finished it Tuesday evening at dinner, and waited until Sunday for results.
If there was a flare-up of inflammation in my skin (the most sensitive tissue) from testing one food, it usually occurred by the third or fourth day after the first of the six test meals. (For example, starting on Monday, I nearly always saw a flare-up, if any, by Wednesday.) I returned to the Elimination Diet and waited two or more weeks for that flare-up to clear as much as it would ever clear at that stage. Sometimes test results were confused and I had to restart.
If there was no flare-up from testing one food, then on the following Monday I tested the next food (in a different category -- for example, a certain kind of beans and then oranges).
Testing every food in every category -- for example, 15 kinds of beans -- is unnecessary. If you test a few foods in one category, and the results are consistent, you can safely generalize, at least temporarily. For example, if you get a reaction from almonds and then, six weeks later, you test and get a reaction from pecans, you can provisionally assume that nuts are a problem as a category. (Afterwards, you may discover some exceptions, as I did with hazelnuts -- listed as alkaline-producing on the PRAL list.)
Be sure to test only one food at each test. Trying to save time by testing two or more foods at once is a waste of time. If there is a flare-up, there is no way to know which of the two tested foods was the cause. Then you must start over again, waiting for the flare-up to diminish.
Writing a log of dates, foods, and results helps keep track of what you are doing. Be sure to record whatever else you are eating at each meal -- including all medications, condiments, and drinks. You might see patterns.