CLOSE to 200,000 hospitalized patients suffer allergic drug reactions each year. Another 50,000 or so are hospitalized for treatment of such reactions.1,2 There may well be more than a million more whose reactions occur away from the hospital and who require no hospital treatment. Perhaps as many as one person of every six who seek medical attention has suffered from an allergic or suspected allergic reaction to a drug at some time.
Although toxic reactions to drugs are much more common than allergic ones, the allergic reactions tend to occur capriciously and explosively, with little or no warning. A reaction can be suspected of being allergic rather than toxic if the offending drug has been used before without any problem, or (as in classic serum sickness) if the reaction did not occur for several days after the drug was first administered. Drug allergy can produce a number of clinical