Long-term outcome of fire ant immunotherapy: Real-world evidence from Southern Thailand

Background: Ant stings, particularly from fire ants, are an important cause of systemic allergic reactions and anaphylaxis. Immunotherapy is considered the only disease-modifying treatment to reduce the risk of recurrence. Objective: This study examined the long-term safety and effectiveness of fire ant rush immunotherapy (RIT) in children and adolescents in Southern Thailand. Methods: We retrospectively reviewed patients who underwent a 3-day fire ant RIT protocol using Solenopsis invicta whole-body extract between 2008 and 2017 at Songklanagarind Hospital. The buildup involved hourly dose escalation to achieve a 0.5 mL maintenance concentration (1:100 wt/vol), followed by injections every 4 to 8 weeks. Systemic reactions were graded by the World Allergy Organization classification, and efficacy was determined from field restings during follow-up. Results: Twenty-five patients (median age 12 years) were included. The rate of systemic reactions per injection was 0.6% during the buildup phase and 0.4% during maintenance. There were no significant differences in age, sex, atopic history, serum immunoglobulin E sensitization, or severity of prior sting reactions between patients with and without systemic reactions. Over a maximum follow-up of 7 years, the cumulative efficacy rate was 76%, with systemic reaction-free survival of 96% at 1 year and 84% at 3 years. Conclusion: Fire ant RIT demonstrated good safety and long-term protection against systemic allergic reactions in this real-world pediatric cohort.