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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.