ALLERGIES: STANDARD COURSE OF IMMUNOTHERAPY
Seventy years ago, a British doctor named Leonard Noon discovered that periodic injections of watered-down grass pollen relieved some people’s hay fever. And that’s how allergy injections 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 hypo-sensitization – can be thought of as vaccination against allergy. And, in effect, allergy injections do operate on the same basic principle as immunization against measles or the flu, which stimulates immunity to disease by injections of a live virus.
The standard immunotherapy routine is relatively simple -perhaps you have already been through it. After several allergy tests, you return to toe doctor for weekly or bi-weekly injections, before or during the allergy season, or year round if necessary. Therapy begins with a small dose and is increased with each injection until you reach a protective dose, which may be continued indefinitely, sometimes for several years. Under certain circumstances, the procedure may be stepped up to daily injections, or even several per day. If, for instance, the pollen season is only three or four months away when a grass allergy is discovered, you may be put through the rush programme. If you’re highly allergic to bees or other venomous insects, your doctor may want to build you up to a protective dose in as little time as possible. (Eight weeks is the minimum, though.) Doctors 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 programme. 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 swellings develop, with heat and discomfort, the dose must be reduced. Of course, that may make the therapy less effective. Anaphylactic reactions are rare, but they do occur, and for that reason some doctors say you should never be left alone for the first hour after an allergy injection (although delayed reactions have been known to occur after one hour). And one study showed that in one out of four adverse reactions, human error – giving the wrong extract or the wrong amount – was to blame (Annals of Allergy).
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 the 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 moulds are really your problem, injections with dust extract won’t help.
Even when skin tests are correct, injections 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 injections probably don’t contain. Immunotherapy for cat and dog dander has not proved effective in most cases. Most allergists generally recommend getting rid of the animals instead. And standard allergy injections 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.
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