There are several disorders thought by some to be caused by food allergies, but the evidence is currently insufficient or contrary to such claims. It is controversial, for example, whether migraine headaches can be caused by food allergies. There are studies showing that people who are prone to migraines can have their headaches brought on by histamines and other substances in foods. The more difficult issue is whether food allergies actually cause migraines in such people. There is virtually no evidence that most rheumatoid arthritis or osteoarthritis can be made worse by foods, despite claims to the contrary. There is also no evidence that food allergies can cause a disorder called the allergic tension fatigue syndrome, in which people are tired, nervous, and may have problems concentrating, or have headaches.
Cerebral allergy is a term that has been applied to people who have trouble concentrating and have headaches as well as other complaints. This is sometimes attributed to mast cells degranulating in the brain but no other place in the body. There is no evidence that such a scenario can happen, and most doctors do not currently recognize cerebral allergy as a disorder.
Controversial diagnostic techniques
One controversial diagnostic technique is cytotoxicity testing, in which a food allergen is added to a patient's blood sample. A technician then examines the sample under the microscope to see if white cells in the blood "die." Scientists have evaluated this technique in several studies and have not been found it to effectively diagnose food allergy.
Another controversial approach is called sublingual or, if it is injected under the skin, subcutaneous provocative challenge. In this procedure, dilute food allergen is administered under the tongue of the person who may feel that his or her arthritis, for instance, is due to foods. The technician then asks the patient if the food allergen has aggravated the arthritis symptoms. In clinical studies, researchers have not shown that this procedure can effectively diagnose food allergies.
An immune complex assay is sometimes done on patients suspected of having food allergies to see if there are complexes of certain antibodies bound to the food allergen in the bloodstream. It is said that these immune complexes correlate with food allergies. But the formation of such immune complexes is a normal offshoot of food digestion, and everyone, if tested with a sensitive enough measurement, has them. To date, no one has conclusively shown that this test correlates with allergies to foods.
Another test is the IgG subclass assay, which looks specifically for certain kinds of IgG antibody. Again, there is no evidence that this diagnoses food allergy.
Controversial treatments
Controversial treatments include putting a dilute solution of a particular food under the tongue about a half hour before the patient eats that food. This is an attempt to "neutralize" the subsequent exposure to the food that the patient believes is harmful. As the results of a carefully conducted clinical study show, this procedure is not effective in preventing an allergic reaction.
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