UNDERSTANDING ALLERGY: MOST TROUBLESOME DRUGS: PENICILLIN

In one of the most comprehensive studies of drug allergy ever conducted – the Boston Collaborative Drug Surveillance Program – doctors collected data from patients in ten hospitals in the United States, plus eight foreign hospitals, covering 22,227 people in all. The results show which drugs most often cause skin reactions (itching, rashes, hives and so on). It’s important to note that women reacted 50 per cent more frequently than men, and that the severity of a person’s illness had no bearing on how likely he or she was to react.

Penicillin. This is not one drug but a general name for a group of antibiotics. Different types of penicillin, made from special moulds, control specific types of bacterial infections -making penicillins the most useful and widely prescribed drugs in the world. Doctors find, however, that from 1 to 10 per cent of the population is allergic to penicillin. Fortunately, most reactions are mild. The chance of a dramatic, explosive reaction is relatively remote; the odds are somewhere between 1 and 4 in 10,000. Even then, only 2 in 100,000 of these result in death. The remainders are kept in check by emergency medical action. (Strangely enough, people who are allergic to penicillin moulds, such as those sometimes found in cheese or around the house, can generally tolerate penicillin.)

Doctors have begun to realize that many people who think they’re allergic to penicillin aren’t really allergic to it after all. Penicillin allergy, it seems, often fades with time if the drug is avoided. Researchers at the Clinical Research Center at Massachusetts Institute of Technology, for instance, tested 300 children who were reputedly allergic to penicillin, to find that only 19 per cent were indeed allergic. The authors conclude that the incidence of penicillin allergy is over-estimated, and that the allergy is not necessarily permanent.

In still another study, researchers tested almost 800 people presumably allergic to penicillin. Nearly half of them were no longer allergic (Journal of Allergy and Clinical Immunology).

These studies don’t mean you should throw caution to the wind and disregard any bad experience you may have had with penicillin. On the contrary: it’s important to know if you have an authentic, active allergy to penicillin. Certain conditions – for example, serious infections, a chronic disease such as cystic fibrosis or venereal disease — depend heavily on penicillin for their medical management. In such cases, doctors conduct a skin test with benzylpenicilloyl-polylysine (called Pre-Pen), which they consider to be the most accurate, lowest risk predictor available for penicillin allergy. Sometimes a doctor can manage penicillin allergy by giving stepped doses of penicillin to desensitize an individual to the drug. If using penicillin is out of the question, the doctor will look for a safe substitute.

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