A bridge between conventional desensit­ization and low-dose neutralization is Dr Len McEwen’s method of enzyme potentiated desensitization.

It is definitely a vaccine approach, whereas Miller’s method of neutralization seems to be more akin to the antidote principle. Briefly, in EPD a cup is taped over the forearm (after the skin on the area has been scarified — scraped repeatedly — to remove the waterproof layers). Under this cup is placed a vac­cine containing dozens of commonly-encountered food and environmental sub­stances, along with an enzyme to make it work (hence the name). The cup is kept in place for 24 hours and then removed.

Antigens leak into the blood over several hours and this creates a favourable antibody response. Obviously the patient will not be desensitized to every ingredient, but since there are dozens of foodstuffs and most common environmental allergens in the mixture, even if only 20 per cent of the items ‘take’ this would mean a significant improvement to many patients.

The doses used are extremely small. In fact, more food appears in the blood after eating a meal than from this technique. It is vital therefore that the patient avoid most foods the day before, the day of and the day after treatment.

The treatment takes up to 12 months to produce a worthwhile improvement in complex food allergies. Environmental allergies, such as grass, pollen and house dust, respond much quicker.

McEwen estimates EPD is about 85 per cent successful. It doesn’t work for chemical sensitivity or insect bites.

Nowadays we dispense with the cup and administer the dose by intradermal injection, except in special cases.

EPD is a compound vaccine: the user-practitioner mixes the appropriate proportions immediately prior to administering the dose.  The modern vaccine contains:

• 1-3 diol, a kind of alcohol which activates the enzyme

•  beta glucuronidase, which appears to act as a lymphokine. It occurs naturally in human blood and is present in the vaccine in an amount equivalent to that normally present in 4 cc of blood. This enzyme, which gives the technique its name, is thought to be responsible for stimulating the Langerhan cells (immunologically active cells in the skin) to migrate to the local lymph glands and ‘reprogramme’ a new population of T-suppressor lymphocytes (those that switch off immune reactions). In the presence of antigen in the appropriate concen­trations, this will result in a satis­factory desensitization. (Conversely, in the presence of antigen at a ‘wrong’ concentration you may get a hyper­sensitization, probably by stirring up helper T-lymphocytes and B-lympho­cytes.)
   

The following mixes are used most frequently:

1. ‘X’ — mixed foods and additives, mixed moulds, mixed pollens, cat/dog, flock, fly mix and bacterial mix.

2. ‘I’ — inhalants alone. This is used to treat hay fever, cat, dog, horse allergies, pure mould and housedust allergies.
    

Separate mixes of odds and ends, laboratory animal hair/dander and sawdusts are also available. So far EPD has not provided any useful means of desensitizing for chemical reactions.
Hay fever and rhinitis usually respond to the first dose of inhalant mix. Two treatments are usually given in all. But doses of EPD are cumulative and a few of the more complex allergic patients will not start to improve until eight doses have been administered over two years.
 

INDICATIONS FOR EPD
A wide variety of conditions respond to EPD, including the following: asthma, eczema, rhinitis, chronic urticaria, angio­neurotic oedema, hyperkinetic syndrome, migraine and chronic headaches, irritable bowel syndrome, inflammatory bowel disease, food-induced psychological states - depression, anxiety - post-viral fatigue syndrome and multiple food allergy.

McEwen draws attention to a combination syndrome of psychological disturbance, irritable bowel and migraine, which he calls PIMS.

SET UP

Foods
Desensitization for foods demands that there are no circulating food antigens at the injection site. This means patients have to go on a diet of foods that have been found from experience rarely to upset EPD, such as lamb, sweet potato, buckwheat, carrot (cooked), celery (cooked), cabbage (cooked), sago, fructose and rhubarb; chicory drink or spring water.

Alternatively, the patient may use one of a number of elemental or synthetic food supplements or replacements, such as Elemental-08, Vivonex (still available in some countries), Pregestimil or Pregomin (Milupa). Dairy and grain-based meal replacers are not allowed.

Inhalants
Treatment for seasonal allergies should be given at least four weeks before the season begins. Desensitization to animal furs may not succeed if the patient returns straightaway to his or her pets. He or she will absorb pet antigen, which finds its way to the injection site in far greater concentration than that in the vaccine, and this may block desensitization. Fortunately allergy to house dust and mites works well without patients having to leave home, but reasonable precautions against house dust mite must be observed, especially prior to EPD.

Micro-organisms
McEwen points out it is not uncommon to see patients who have become sensitized to their own gut flora. In these cases it is necessary to reduce the bowel antigen load starting at least 10 days prior to a dose of EPD. The commonest problem is Candida allergy and this must be pre-treated with a suitable antifungal such as Nystatin. Allergy to gut bacteria often goes unnoticed and untreated. Preparatory treatment may be satisfactorily carried out with antibiotics such as tetracycline or nifuroxazide.

FAILURES
EPD can be blocked by a number of factors. If one or more of these factors is present the physician must decide whether to defer treatment until conditions are more suitable:

1. excess exposure to inhalants, foods, Candida, fumes, etc. close to the time of treatment
2. incidental infection such as a cold or flu
3. stress
4. nutritional agents: excess vitamin C, cod liver oil, evening primrose oil at treatment time (or large excess at other times)
5. drugs: paracetamol, aspirin, NSAIDs, high-dose oestrogen (the Pill or HRT implants), progesterone-like drugs, H2 histamine antagonists (notably cimetidine or Tagamet), alpha and beta sympa­thomimetics (ventolin, bricanyl in large doses), cyclophosphamide, opiates, tri- methoprim, Septrin and anti-malarials.

SAFETY
Whenever antigenic material is injected into any person there is always the theoretical risk of anaphylaxis. Reactions to the ‘conventional’ desensitizing injections are common because large amounts of antigen are injected. In fact deaths have occurred and this method of injecting large amounts of antigen is no longer considered justifiable.

With EPD far smaller quantities of antigen are used, which greatly increases the safety margin. Over 30,000 treatments have been given by cup since 1966. No patient has been admitted to hospital to treat an emergency provoked by EPD. This includes patients who have severe asthma or who have previously suffered acute anaphylactic reactions to multiple foods.

EPD is now usually administered by intradermal injection, except for the high-dose inhalant vaccine, which must only be given by the cup method. However, the current practice is to retain the cup technique for patients who may be especially at risk of anaphylaxis, even for administering the low-dose vaccine. This bolsters the safety element greatly.

Insect bites have not been included in EPD for safety reasons.

NUTRITIONAL SUPPLEMENTS AFTER EPD
Increasing the short-term availability of zinc appears to improve the effectiveness of EPD.  So does the administration of folic acid and vitamin D₃. The average response to treatment is accelerated by giving additional supplements of these substances for approximately three weeks after each dose.

Generally these nutritional supplements are not used after hay fever treatments, although they may be added if the response to a first treatment has been poor. Inadequate patient nutrition must be tackled as a separate problem. As with any other approach, most patients benefit from multivitamin and mineral supplements.