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What is anaphylaxis?
Anaphylaxis is the word used for serious and rapid allergic reactions usually involving more than one part of the body which, if severe enough, can kill.
The word anaphylaxis was coined when scientists tried to protect dogs against a poison by immunising them with small doses. Far from being protected, the dogs died suddenly when they got the poison again. The word used for protection by immunisation is 'prophylaxis', so the scientists coined the word 'anaphylaxis' to mean the opposite of protection. What the scientists saw in the dogs helped them to understand that the same can happen in humans. This helped us to understand asthma and other allergies too, because they work in a similar way.

Scientists now use the word 'anaphylaxis' to mean any immune reaction of this type, even if it is not serious. But most doctors use it to mean a life-threatening rapid allergic reaction.

Unfortunately this kind of 'harmful immunisation' happens to a few of us not just from injections but from ordinary foods such as nuts. Quite literally, "one man's meat is another man's poison". Our immune system, which is there to protect us from infection, goes wrong and harms or even kills us.

Injections of many kinds occasionally cause anaphylaxis. Penicillin, injected clot-busting drugs used after heart attacks, and a host of other kinds of injection can occasionally do to human beings what the experiments did to dogs. Thank goodness we now understand vastly more about anaphylaxis, though we still need research to answer important questions.

There are yet other causes of anaphylaxis. You will see more about some of those below. Anaphylaxis has become an important issue in medicine and for the increased numbers of people who have had an attack of anaphylaxis.

Why the increase? When medicines are the cause, the explanation is likely to be that we are simply using more medicines, and that newer medicines which are proteins are more likely to cause anaphylaxis. But this does not explain why foods should be causing anaphylaxis more often. For some reason all the common allergies such as hayfever, allergic asthma and food allergy have become more common. Researchers have definite ideas about why this might be so.