18th March 2024

Drug Induced Anaphylaxis (DIA)

Incidence of DIA is increasing with development of new medications and increased awareness and reporting of cases. As discussed above, medications are common causes of anaphylaxis and are associated with higher mortality than reactions caused by venom or food; drug-induced cases represent up to 58% of fatal anaphylaxis. Non-steroidal anti-inflammatory drugs are the most common culprits of DIA followed by beta-lactam antibiotics, particularly amoxicillin. Modern radiocontrast media is less frequently associated with DIA due to non-ionic, low osmolar agents. Proton pump inhibitors are increasingly frequently linked to DIA, most commonly lansoprazole. Additionally, it is important to recognise the risk of topical agents including chlorhexidine and latex. Excipients in vaccines such as egg lecithin and recently polyethylene glycols in COVID vaccines, as well as a variety of medications including proton pump inhibitors and laxatives, have been identified as anaphylaxis culprits.

Risk factors for increased severity of reactions include increasing age and intravenous administration. Co-factors are also known to influence DIA risks, such as co-morbidities (including asthma), alcohol, menstruation and psychological stress.

Immunologic anaphylaxis can result from both IgE dependent and IgE independent pathways. Certain drugs are more commonly associated with one pathway rather than the other (such as penicillin associated with IgE) and some, such as contrast media, can be associated with both. IgE dependent anaphylaxis requires sensitisation during which T helper cells are activated (in this case by the medication) and induce IgE production specific to the antigen. The IgE independent pathway is orchestrated by IgG or complement; the mechanism is not yet fully described in humans. Finally, as described above, an anaphylaxis reaction can result from direct activation of mast cells and basophils.  The sensitisation process is not required in anaphylactoid reactions.

Latex-fruit syndrome

There is a significant crossover observed between allergic reactions to certain foods and latex. Up to 40% of patients with latex allergy demonstrate reactions to one or more fruits including strawberry, kiwi, banana and tomato. This is hypothesised to be due to structurally similar proteins on the surface of latex and specific foods. Although the term “latex fruit syndrome” is used, the phenomenon is not limited to fruit and is observed with a variety of vegetables, too. This syndrome demonstrates the importance of a careful allergy history as well as an awareness of cross-sensitivity.