Pre-race self-reported medical conditions and allergies in 133 641 Comrades ultramarathon (90km) runners - SAFER XXIII.

Voluntary completion of two open-ended questions identified chronic medical conditions and/or prescription medication use in 6.9% and allergies in 7.4% of ultramarathon race entrants. This is lower than that reported for other races that implemented compulsory completion of a more comprehensive pre-screening questionnaire. Despite potential under-reporting, a pre-race self-reported history of chronic medical conditions and allergies was associated with a higher risk of race-day MEs.