Cofactors in Anaphylaxis: Insights From the European Anaphylaxis Registry

The role of cofactors contributing to anaphylaxis severity remains unclear.

We analysed data from the European Anaphylaxis Registry (2007-2024) to determine the impact of suspected cofactors on reaction severity. Adjusted odds ratios (aOR) were calculated for the number of organ systems affected, but also two severity classification systems (Ring/Messmer and Brown).

At least one suspected cofactor was reported in 8310 cases (49%) out of 16,915. Cofactors were less frequently suspected among younger patients (< 18 years: 26% and ≥ 18 years: 59%). Medication was the most common suspected cofactor in adults (41%), followed by exercise (27%), which was in parallel the most frequent suspected cofactor in children (19%). Emotional burden (children 3%/adults 8%), alcohol (0.4%/8%), sleep deprivation (0.5%/2%) and menstruation (2%/4%) were less commonly reported. We observed a trend between reaction severity and an increasing number of suspected cofactors. Among suspected cofactors, we observed consistent effects on anaphylaxis reaction severity for acute infections among children and alcohol consumption among adults in food-induced reactions. Moreover, we identified an association between the presence of a suspected cofactor(s) and an increased time interval between exposure and onset of symptoms across all age groups in food-induced anaphylaxis.

Our data suggest an age-dependent role of suspected cofactors in anaphylaxis severity. Clinicians should explore the presence of cofactors in patients who experienced anaphylaxis, in particular in those with prolonged time intervals between exposure and reaction onset.