Forego Food-Allergy Tests?

Adverse reactions to certain foods may cause a wide range of conditions, including asthma, rheumatoid arthritis, migraines, sinusitis, irritable bowel syndrome, fatigue, and others. Hidden or masked food sensitivity is one of the most common causes of unexplained symptoms.

Blood tests that measure the response of a patient's immune system antibodies to suspect foods are now being promoted as a useful way to diagnose hidden food allergies, but there is little or no proof that these tests are effective, and there is some convincing evidence that they are not.

There are several theoretical reasons why blood tests that measure antibody levels may not be useful in assessing food sensitivity:

• In many instances, adverse reactions to foods do not involve the immune system. Instead of evoking the production of antibodies, the offending foods appear to be mediated by prostaglandins, endorphins and other non-immune processes.
• Biologically active compounds in foods, such as benzodiazepines, caffeine, endorphin-like molecules, etc., may induce sumptoms which are not immune system reactions.
• Certain components in foods may produce true allergic reactions, but the antigens (the chemicals initiating the allergic reaction) may not be the ones measured by a particular blood test.
• Some adverse reactions are caused by substances produced during cooking or processing. Blood tests designed to identify only native food proteins would miss these.
• Some antibodies successfully neutralize food reactions, but do not cause symptoms. If these antibodies show up in blood tests, their presence may be mistakenly believed to indicate an allergy.
• Contaminants in the foods from which test antigens are prepared, such as mold or bacteria, could produce an antibody response that might be mistaken for a food allergy.

All these factors suggest that blood tests for food sensitivity could be highly unreliable. But, more telling is the fact that some of the commercial labs offering food allergy testing cannot even reproduce their own results. In one case, six samples—all drawn from the same patient at the same time—were sent to three different labs. Two of the labs returned results with "incredibly high" variances between the samples, indicating that the testing was unreliable.

According to one expert, patients should not waste their money on questionable food-allergy blood tests. A surer and less expensive approach to the diagnosis of food sensitivity is an elimination diet. While time-consuming, and requiring effort by both patient and doctor, this method shows most clearly what foods are causing the problems.   Based on information in: Townsend Letter for Doctors & Patients, Jan 1998