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Allergy Desensitisation

What it involves for you

Desensitisation has rather dropped out of favour with British doctors since 1986 because of the dangers associated with the old-fashioned allergy shots that were given for hay-fever. There are still doctors who remember the old days and will tell patients that “desensitisation was banned because of its danger.” This is not entirely true, nor entirely fair because continued research in the last 20 years has produced improved forms of desensitisation that are far safer, and are already available in America and Europe (where allergists are better organised). For a simple case of hay-fever nowadays I might well start using one of these newer treatments, once they are marketed in the UK.

But in any case, by 1986 I had stopped using conventional desensitisation because two new methods, both extremely effective and extremely safe, had become available. I can use both, and will choose the most appropriate depending on the individual patient’s needs and wishes. Both require small injections into the skin, using a fine needle only slightly wider than a human hair. The pain is minor and lasts only a second, though there is often some redness, itch or swelling ten minutes later, lasting perhaps a half-hour or so, and occasionally a delayed reaction next day. Tens of thousands of patients have been treated with these methods over the last 30 years, and neither method has ever caused a death (unlike conventional desensitisation). Nevertheless, allergists obviously remain alert, trained and prepared for unexpected reactions.

Enzyme-potentiated desensitisation (EPD)

This involves one (sometimes more than one) small injection into the skin, usually given every three months until a useful degree of protection has been achieved. The big advantages of this method are that it requires no testing and very few injections, also the costs are low and spread over the months. The big disadvantage is that it is rather slow – for a simple hay-fever you would need one injection 5-6 months before the start of the season and another 2-3 months before, so you have to be well organised in advance. For technical reasons you cannot always choose, at my practice, a treatment day to suit yourself – you may have to have your treatment on a pre-determined day when other patients will also be receiving theirs (this reduces the cost to all).


This requires several small injections, into the skin, using several different strengths of the suspected substance. The kind of reaction given by the skin tells the operator exactly the right strength (the “neutraliser”) to use in your treatment. If many substances are suspected, you will need perhaps five injections for each substance, given in a row into the skin, and if a good neutraliser is not found straight away, different strengths will have to be administered until it is found. Once the neutraliser is known, the patient takes it daily at home, either as drops under the tongue (or into the nose if appropriate), or by self-injection depending on age and other factors.

Neutralisation can usually be tailed off and stopped eventually, once full desensitisation has been achieved (see below).

So the big disadvantage of neutralisation is that it involves more injections, each with its own discomfort. The pain is negligible, but the fear (especially in children) can be a problem. Most patients manage. The big advantage is speed. If a hay-fever patient comes for testing on a high-pollen day full of symptoms, he/she will usually leave the clinic half-an-hour later already feeling better, and will often be symptom-free (or almost so) within a few days. You do not therefore need such good pre-season organisation. (This speed actually causes many doctors to disbelieve the whole thing, it just seems too good to be true - although it is true).

The cost of neutralisation testing depends on how many substances are to be tested. If only one or two substances are involved, neutralisation will work out cheaper than EPD. For more than about a dozen substances, EPD will be cheaper. On the other hand, the speed of neutralisation offers the possibility of testing out the method in advance, on a few known allergens and before major money is committed, to see if it is going to work for you.

Don’t ask me how desensitisation works. In the 100 years since Leonard Noon first started giving pollen injections for hay-fever at St Mary's’Hosiptal, no-one has convincingly explained their mode of action (although there have been numerous theories). Judging by clinical observations, both conventional injection therapy and EPD gradually slow down the immune mechanisms that produce the IgE antibodies – the “harmful” antibodies that lead to inflammation. I picture it like easing back on the accelerator of a car. Neutralisation seems to more like disengaging the clutch, leaving the engine racing (the IgE antibodies stay high but they are somehow disconnected from the target organs and no longer cause symptoms). Then, after weeks or months of neutralisation, true desensitisation also occurs. There are also some newer forms of conventional desensitisation in development which look very promising, but they are not yet available in the UK so for now I will summarise only the two methods which are:




Rather slow


Fewer jabs

Many small jabs - about 5 per substance

Cheaper if many allergies involved

Cheaper if few allergies (e.g. hay-fever)

Effective in 80% of patients

Effective in 80% of patients (not necessarily the same 80%)

Often given on fixed days only

You can choose the day of testing

Treatment on same day

Testing on agreed day followed by treatment to be taken at home daily

May require special diet and supplements

May require special diet if food allergies are involved

Can usually be stopped once full desensitisation is achieved.

Can usually be stopped once full desensitisation is achieved

NB. Neither method works invariably for all patients.
Bear in mind therefore:

The patient cannot be sure until several treatments have been given whether or not EPD works for him

Neutralisation can often be pre-tested reasonably cheaply, to make sure the method works for this individual.

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