Food Allergies

"Food allergies are most often of the delayed type, persisting for some time after the allergic substance has been eliminated and recurring only after repeated daily exposures, once symptoms have improved.
Fixed allergies to gluten containing grains (such as wheat) and dairy products is common, however, and reactions to those foods may persist throughout life, fluctuating in sensitivity from time to time. Viral infections and other illnesses can reactivate food allergies. Allergy is usually the result of repeated exposures to a specific substance or food. The more often the exposure, the more likely it is to provoke an allergic response. For unknown reasons, some foods are tend to be much more allergic than others.
Unless all sensitizing foods are eliminated during the same period of time, for a month or more, there may not be enough time for symptoms to clear. Multiple allergies are additive. Eliminating only one or a few of the sensitizing substances may not be adequate to see improvement, and the diagnosis will be missed.
If symptoms improve and if you feel better on [an elimination] diet, it means that something you eat or drink on a regular basis is either causing or contributing to the severity of symptoms.
You may experience withdrawal symptoms and strong cravings during the first week or two on the diet. Paradoxically, withdrawal and cravings are also symptoms of food allergy. After a few weeks of elimination, cravings for the offending foods will disappear. Cravings are not related to nutritional factors.
Observe carefully for changes in nasal or lung congestion, mucous, fatigue, foggy thinking, digestive disorders, constipation/diarrhea, bloating, gas, fluid retention, pain, mood swings, joint aches, urinary problems, drowsiness after meals, and other symptoms that can be caused by unsuspected food allergies."(1)

(1) http://www.drcranton.com/elimination_diet.htm