Seventy years ago, a British doctor named Leonard Noon discovery that periodic injections of watered down grass pollen relieved some people’s hay fever. And that’s how allergy shot were born. The whole idea does seem contradictory – to gain relief by administering the very stuff that makes you miserable.

Apparently, however, steady doses of allergy extract exhaust allergic antibodies, building up an individual’s tolerance to allergy triggers. Immunotherapy for allergy – sometimes called desensitization or hyposensitization – can be thought of as vaccination against allergy. And, in effect, allergy shots do operate on the same basic principle as immunization against muscles or the flu, which stimulates immunity do disease by injections of a live virus.

The Standard Course

The standard immunotherapy routine is relatively simple – perhaps you have already been though it. After several allergy tests, you return to the doctor for weekly or biweekly shots, before or during the allergy season, or year round if necessary. Therapy begins with a small dose and is increased with each shot until you reach a protective dose, which may be continued indefinitely, sometime for several years.

Under certain circumstances, the procedure may be stepped up to daily shots, or even several shots per day. If, for instance, pollen season is only three or four months away then a ragweed or grass allergy is discovered, you may be through the rush program.

If you’re allergic to bees or other venomous insects, your doctor may want to build you up to a protective dose in as little as possible (eight weeks is the minimum, though). Doctor have also successfully desensitized people who require antibiotics against allergy to penicillin. Ultimately, the same number of injections is needed whether you go the leisurely route or the stepped up program.

And the potential for adverse reactions is about the same (oh yes – there’s always that chance). Occasionally some people experience a little swelling and itching at the site of the injection for a day or so. If larger or more persistent swelling develop, with heat and discomfort, the dose must be reduced. Of course, that may make the therapy less effective.

An aphylactic reactions are rare, but they do occur, and for that reason some doctors say you should never left alone for the first hour after an allergy shot (although delayed reactions have been known to occur after one hour). And one study showed that in one out four adverse reactions, human error – giving the wrong extract or the wrong amount – was to blame (Annals of Allergy, April, 1982).

The optimal dose, as it's called is one that’s too small to trigger a bad reaction, yet large enough to relieve your symptoms. Occasionally, treatment will fail to bring relief simply because the extract sat on the shelf too long or wasn’t stored properly, thereby losing potency.

Aside from general lack of appeal of enduring countless needles, standard immunotherapy has some limitations. Needless to say, if the skin tests upon which the therapy is based are inaccurate – which they sometimes are – the therapy can’t possibly work. In other words, if the scratch test indicates that you’re allergic to dust, but molds are really your problem, shots with dust extract won’t help.

Even when skin tests are correct, shots have been developed for just a few select airborne allergens. Because grass pollens tend to cross react with one another, treatment with one grass pollen will very often reduce reactions to any grass pollen.

But people who are allergic to dust aren’t always so lucky – they're exposed to an almost limitless variety of dust ingredients, some of which shots probably don't contain. Immunotherapy for cat and dog dander has not proven effective in most cases. Most allergists generally recommend getting rid of the animals instead.

And standard allergy shots simply don't exist for food allergies; poison ivy; bites by flies, fleas and mosquitoes; hives; eczema; allergic contact dermatitis; or migraine headaches. Fortunately, standard immunotherapy does seem to give fairly good protection against one of the most dreaded allergies – reactions to stinging insect venom.

But because of the rather frequent incidence of systemic reaction, venom immunotherapy is generally reserved for people who are considered to be at risk for serious reactions. This includes anyone who has had anything more than a large local reaction and who reacts to a skin test, as well as people who become asthmatic after stings and adults who react with hives.

Even for those allergies for which it works, immunotherapy is rarely the only form of treatment necessary. Often, drugs such as bronchodilators and antihistamines are still used to achieve more complete relief. And, of course, drugs are frequently the mainstay of medical treatment for those allergies for which no immunotherapy has been developed.