Overview

Enzyme Potentiated Desensitization (EPD) is an alternative form of "allergy shot" originally popularized in the UK in the 1960s by a man named Leonard McEwan. It involves injection of very low levels of an allergen, combined with the naturally occurring enzyme beta glucuronidase. EPD proponents claim that this method gets to the root of allergy problems, and produces permanent benefits by "retraining" the immune system. Supposedly, it can successfully treat literally hundreds of medical conditions, from rheumatoid arthritis to epilepsy. However, the evidence used to support these assertions falls considerably short of meaningful.

For example, EPD proponents cite "studies" that show EPD offers cure rates approaching 85% for numerous illness. However, this body of evidence is scientifically unreliable. The cited research was of the type called an "open, uncontrolled" study. This means that researchers (or practitioners) administered EPD to people and then noted whether they saw benefit. While positive findings in this type of investigation may seem intuitively to mean something, this is an illusion. Here is the underlying problem: for most conditions, a high percentage of people given placebo will improve or appear to improve, and often dramatically.

The reasons for this fact are complicated and surprising; a detailed explanation is given in Why Does This Database Rely on Double-blind Studies? The bottom line is that for researchers to actually show a treatment to be effective, they must compare it against placebo treatment. Furthermore, they must conduct the study in a double-blinded fashion, meaning that neither the practitioners nor the patients know who is getting real treatment and who is getting placebo. Finally, such studies must be randomized, meaning that people are assigned to the treatment or the placebo group by random chance (such as flipping a coin) rather than by choice. Only two such randomized, double-blind, placebo-controlled trial has been performed on EPD. One found benefit; the other did not.

In the first double-blind, placebo-controlled study, 183 people with a history of consistent hay fever were treated with EPD or placebo and followed throughout the hay fever season.1 The EPD preparation contained beta glucuronidase, 1,3-cyclohexanediol, protamine sulphate, and a mixed extract of allergens, including pollens, fungal spores, cat and dog danders and dust mite. The fake treatment contained only saline. Neither the researchers administrating the injections nor the study participants knew which was which. Both groups improved markedly. However, there was no difference in symptoms between the two groups, as measured by problem-free days, quality of life scores or symptom severity scores.

A slightly smaller study did find benefits. In this double-blind study of 125 children, use of a single dose of EPD reduced hay fever and asthma symptoms as compared to placebo.3

At present, therefore, the most that can be said about EPD is that equivocal evidence exists regarding its efficacy for allergies. Benefits for any other conditions remain entirely speculative at this time.

A similar scientific inadequacy exists regarding claims made about how EPD works. One EPD website states the following: "EPD stimulates the immune system to produce new T-suppressor cells ... These take 3 to 4 weeks to mature before they can begin their task of disabling mis-coded T-Helper cells. Essentially, this is a re-training program so the body does not react to those substances contained in the shot. The mis-coded cells are a part of the chain that stimulates the production of histamine, the major trigger of allergic response."2 While this claim may sound impressive on the surface, it succeeds only as advertising; as science, it strays much too far from established facts.

Safety Issues

Whether or not EPD is effective, it does appear to be safe. No serious adverse reactions have been associated with its use. Although in theory allergic reactions could occur in response to EPD injections, the amount of allergen used in EPD is so much lower than the amount used in a normal "allergy shot" that these may not, in fact, occur.

EPD proponents claim that there can be a temporary aggravation response that is part of the healing process; however, this has not been documented.