Olive Pollen Allergy Shots Show Mild Safety Profile in Spanish Real-World Study

A multicenter study of patients in Spain treated with accelerated subcutaneous immunotherapy against olive pollen has reported predominantly mild adverse reactions and improvements in nasal, non-nasal and asthma symptom scores over one year of follow-up. The OLGA study, conducted at 16 allergy centers across Spain, analyzed real-world data from 245 patients with IgE-mediated allergic rhinoconjunctivitis and/or asthma who were sensitized to olive pollen, with or without additional grass pollen sensitization.

Allergen immunotherapy is described in the study as the only treatment capable of modifying the natural course of IgE-mediated allergic diseases induced by aeroallergens. For olive pollen allergy, a major burden in Mediterranean populations, the authors note that specific data on Olea europaea extracts, used alone or combined with grass pollen, have remained limited. The OLGA study was designed to address that gap under routine clinical practice conditions rather than in a controlled trial setting.

The treatment examined was subcutaneous immunotherapy administered according to a cluster schedule using hypoallergenic depot extracts. In cluster schedules, doses are escalated over fewer visits than in conventional regimens, allowing patients to reach maintenance dosing faster. According to the study’s background, cluster schedules with depot extracts enable this faster dose escalation while maintaining a favorable safety profile, but real-world evidence for olive pollen products had been scarce.

Safety findings were central to the analysis. Adverse reactions occurred in 27.3% of the 245 patients and were predominantly mild local reactions. The researchers reported no grade 3 or higher systemic reactions, no hospitalizations, and no treatment discontinuations due to adverse reactions. Safety and clinical outcomes were assessed over one year through physician-reported adverse reactions and changes in symptom scores.

Clinical outcomes also shifted favorably during follow-up. Nasal symptom scores decreased by a mean of 5.05 points, non-nasal scores by 4.00, and total scores by 9.06, all with p-values below 0.001. The annual number of asthma exacerbations fell by a mean of 2.7, also reaching p < 0.001. Because these are before-and-after changes in a retrospective, uncontrolled analysis, they describe observed changes during treatment rather than effects proven against a placebo or alternative regimen.

The proportion of patients meeting predefined thresholds for clinically relevant change exceeded 93% across all evaluated symptom domains. The authors report that similar outcome patterns were seen whether patients received olive-only extracts or products combining olive and grass pollen, suggesting the observed patterns were consistent across both formulation types in this cohort.

The study population was predominantly young adults: 51% were male and the mean age was 26.6 years. As a retrospective, real-world analysis, the study reflects how these products were used in routine allergy practice across the 16 participating Spanish centers, including physician-reported rather than patient-diary outcomes, and it cannot establish causality in the way a randomized controlled trial would.

In their conclusions, the authors state that the study provides information on the safety profile and clinical outcomes observed in patients receiving depot allergoid subcutaneous immunotherapy in a cluster schedule, and that the findings contribute to the evidence describing accelerated immunotherapy schedules for patients sensitized to olive pollen under routine clinical practice conditions. The article was published open access in Allergy, Asthma & Clinical Immunology on 11 October 2026.

Subject of Research: Real-world safety and one-year clinical outcomes of cluster subcutaneous immunotherapy with olive pollen extracts in patients with allergic rhinoconjunctivitis and/or asthma

Article Title: Real-world safety and clinical outcomes of cluster subcutaneous immunotherapy with olive pollen extracts, with or without grass pollen, in patients with allergic rhinoconjunctivitis and/or asthma

Article References: Alcántara-Villar, M., Martín-Casañez, E., Rodríguez, M. T. P., Betancor, D., Crespo-Moreira, P., Sánchez-García, S., Barroso-García, B., Escudero-Díez, C., Bejarano-Rojas, J. A., Sola-Martínez, F. J., the OLGA Study Group, Capilla, M. R., Jiménez, A. C., Fernández, N. C., Montes, A. T., Gutiérrez, V. J. A., Monge, M. V., Rubio, L. B., Ruiz, C. L., … Campos, J. G. (2026). Real-world safety and clinical outcomes of cluster subcutaneous immunotherapy with olive pollen extracts, with or without grass pollen, in patients with allergic rhinoconjunctivitis and/or asthma. Allergy, Asthma & Clinical Immunology. https://doi.org/10.1186/s13223-026-01074-6

Image Credits: AI Generated

DOI: 10.1186/s13223-026-01074-6

Keywords: allergen immunotherapy, olive pollen, subcutaneous immunotherapy, cluster schedule, allergic rhinoconjunctivitis, asthma, real-world study, adverse reactions, Olea europaea, Spain, symptom scores, allergy