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Other risk factors that may
contribute to the occurrence or severity of an anaphylactic reaction include
age (most fatalities are over age 45) and gender (more common in males). The
incidence and/or severity of anaphylaxis to radiocontrast media, Hymenoptera
stings, neuromuscular agents, and plasma expanders are greater in adults
than in children. Females have an unexplained greater incidence of
anaphylaxis in general and a greater incidence in particular to
radiocontrast media, neuromuscular agents, latex, and aspirin compared to
males. In contrast, reactions to Hymenoptera stings occur more frequently in
males than in females. The constancy of antigen administration may
mitigate the occurrence or severity of a reaction, and interruption in
administration of allergen can lead to a very severe reaction on the next
exposure. For example, when there is a period of days or weeks without the
antibiotic or ASA, the next dose is more likely to cause anaphylaxis. Also,
beekeepers will describe minimal reaction to stings during the season, but
after not being stung all winter, the first or second sting of the new
season is more likely to cause anaphylaxis. When a longer time (years) has
elapsed since the last reaction there is a lower risk of reaction to another
exposure: ten years after anaphylaxis to penicillin or insect sting, if
there has been no intervening exposure, the risk of reaction to the next
exposure is in the range of 10-20%. Food allergy has also been noted to
disappear more commonly when there is strict avoidance for three years.
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