The Spanish REAL project: expert allergist guidance on allergen immunotherapy based on mixtures from different allergenic sources

Background: The increase in polyallergy highlights allergen-specific immunotherapy (AIT) as a crucial therapeutic option for these patients. It is the only etiological treatment capable of modifying the natural course of allergic diseases. Its use, particularly with mixtures from different allergenic sources, varies across regions. In Spain, geographic and environmental diversity leads to complex, heterogeneous sensitization patterns not fully addressed by international guidelines, reinforcing the need for context-specific recommendations integrating current evidence and real clinical practice. Objective: To establish general recommendations for managing polyallergic patients undergoing AIT with mixtures of different allergenic sources in Spain. Methodology: Eight regional meetings with 61 experts were held across Spain using the Workmat® methodology: evidence-based exercises designed to facilitate discussion and consistent data collection. Results: Experts agreed that polymerized allergen extract mixtures offer several advantages over AIT with simultaneous use of individual allergen extracts, as they allow multiple sensitizations to be treated in a single application, simplifying the treatment without compromising safety or efficacy while also saving time and costs and improving treatment adherence. Furthermore, the use of polymerized allergen extracts has improved efficacy and safety in AIT. It is essential to perform an individualized evaluation, according to the type of extract, the mixture, and the patient's comorbidities. Conclusion: The increasing prevalence of polyallergy has emerged as a growing challenge in routine clinical practice. In this context, AIT using polymerized allergen extract mixtures, at optimal doses, tailored to individual sensitization profiles represent a practical and effective approach for managing polyallergy in the Spanish clinical setting.