Enzyme-potentiated desensitisation (EPD) is a treatment which aims to reduce the sensitivity of patients to substances causing allergy and intolerance and thereby reduce symptoms, whether due to allergens in the air (for example, pollens, dust mite, animal danders), in food, or even environmental chemicals. EPD may be used to treat conditions such as hay fever, dust mite or animal allergies, allergic asthma and eczema, and food intolerances.
Developed about forty years ago by Dr Len McEwen, an allergist working at St Mary's Hospital, London, EPD has been in constant use since then in the United Kingdom, mainland Europe (particularly Italy) and the United States by small numbers of allergists. In the UK it is available privately from members of the British Society of Ecological Medicine (www.ecomed.org.uk) and on the NHS at the Royal London Hospital for Integrated Medicine (formerly the Royal London Homeopathic Hospital) where it has been used since the 1970s and where about five hundred patients are currently receiving EPD.
In EPD, tiny doses of purified allergy-causing substances (allergens) are given by injection together with an enzyme, beta-glucuronidase, which potentiates (enhances) desensitisation to the allergens injected, hence the rather complex-sounding name. The enzyme is naturally occurring in humans where it helps to break down complex carbohydrates in many organs. Tiny amounts of naturally occurring sugars are also used.
In EPD, many allergens are given together in standard mixtures. For instance, in inhalant allergies such as hay fever, the mixture includes 62 tree and grass pollens, 6 mite and dust extracts, 15 animal danders and 70 fungal extracts. For food intolerances, a standard mix of 58 food extracts is used, as well as the inhalant allergens. The use of such a wide range of allergens aims to "damp down" the allergic tendency of the immune system as well as treating the specific allergy. The dosage is usually the same on each occasion. Injections are given at two- to three-monthly intervals initially, for up to a dozen injections, and then treatment is spaced out and can even be stopped if patients have significantly benefited. Allergen exposure must be avoided, particularly in the twenty-four hours either side of an injection, and if treating food intolerances, a restrictive diet must be eaten for those forty-eight hours. Certain medications such as painkillers, and procedures such as dental work, should be avoided for up to three weeks after an injection.
EPD may be contrasted with the conventional type of desensitisation used in most NHS allergy departments, known as specific immunotherapy (SIT). In EPD, injections are given intradermally (into the skin) at intervals of two to three months, whereas in SIT injections are given subcutaneously (under the skin) and must be given at weekly intervals in increasing doses to begin with, then sometimes 4-6 weekly for three years. In EPD, the allergen is given in tenfold smaller doses than SIT, about the same size dose as a skin prick test. This makes it free from the rare but serious allergic reactions which may occur with SIT, limiting its use to very severe allergies and making it unsafe to use in asthma. In a safety surveillance study, over a third of a million doses of EPD were given without serious incident. Another difference is that with SIT only a single allergen can be given, so patients with multiple allergies cannot be treated, which they can with the multiple allergen EPD approach. However, SIT is the only treatment available for allergy to bee or wasp stings, and neither approach can at present be used for severe food allergy (such as immediate-type peanut allergy) or latex allergy.
A major difference between EPD and SIT is in the scientific evidence to justify its use. There is consistent evidence from many studies of the good effectiveness of conventional SIT for hay fever and venom allergy, and emerging evidence for sublingual (under the tongue) immunotherapy tablets in hay fever. The evidence for EPD is inconsistent. Several small studies, mostly conducted in the 1980s, showed promising results using EPD in a variety of conditions including hay fever, dust allergy, migraine, ulcerative colitis, and childhood attention deficit hyperactivity disorder (ADHD). This prompted a large, well-conducted study of EPD in grass pollen hay fever (conducted by Dr Michael Radcliffe at Southampton University).
Published in the British Medical Journal in 2003 (volume 327 pages 251-254), the study did not confirm the earlier studies but showed no difference between EPD and placebo (dummy) injections. The study lasted for a single season and it is possible that benefits may have emerged if the study had continued for two or three seasons. It may have been that EPD achieved benefits in some patients, but did not show a statistically significant improvement across the whole study population. Finally, there was some suggestion that the EPD injections used in the study, although stringently prepared to a good manufacturing practice standard, might have been subject to a loss of desensitising potency. However, the study has cast some doubt on the effectiveness of EPD for hay fever.
The results puzzled those physicians seeing apparent and long-lasting benefits of EPD in daily practice for many patients. Often, these patients try EPD as a last resort, having had conventional and sometimes alternative treatments without success. They are therefore initially sceptical about EPD, which makes it unlikely that the benefits should be attributed to the effects of positive expectation. Furthermore, significant changes may be seen not just in symptoms but in more objective measures such as the extent of eczema, the severity of asthma, and the use of orthodox medication.
The unfavourable state of the current evidence makes it unlikely that EPD will become more widely available on the NHS, despite its relative safety. However, the good results seen in practice over thirty years, and the many patients requiring EPD to maintain good health, mean that it will continue to be offered as an option alongside conventional immunotherapy at the Royal London Hospital for Integrated Medicine.
Dr Berkovitz is a Consultant Physician at the Royal London Hospital for Integrated Medicine, London, the only hospital in the UK which provides EPD on the NHS and accepts patients from all geographical areas who are referred by their GP. For enquiries about NHS or private treatment contact Dr Berkovitz's secretary on 020 7391 8873.
EPD reduces sensitivity
Written by Administrator