Q. Once a person has had an anaphylactic reaction to a substance
Q: Once a person has had an anaphylactic reaction to a substance, will all subsequent exposures invariably lead to similar or worse reactions?
There is no question that recurrent reactions can follow re-exposure. As it turns out, however, the probability as reported in the medical literature is considerably less, about 50% for bee stings, for example. These re-exposure reactions can be less severe than the prior reaction.
Taking reasonable steps to avoid re-exposure is as important as being prepared to recognize and treat a reaction should it occur. For some people with recurrent severe reactions, immunotherapy (aka desensitization) can be a very effective deterrent. It is equally important to remember, however, that based on these statistics, not everyone needs to be treated following a re-exposure. Only treat those who develop signs and symptoms consistent with a true anaphylactic reaction.
