Experimental Allergy – Research Article Int Arch Allergy Immunol 2022;183:1166–1177 Measurement of Horse Allergens Equ c 1 and Equ c 2: A Comparison among Breeds Susanne Victor a Erik Lampa b Anna Rask Andersen a Guro Gafvelin c Hans Grönlund c Lena Elfman a a Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden; b Department of Medical Sciences, Clinical Epidemiology, Uppsala University, Uppsala, Sweden; c Department of Clinical Neurosciences, Therapeutic Immune Design Unit, Karolinska Institutet, Stockholm, Sweden Received: October 27, 2021 Accepted: June 9, 2022 Published online: September 1, 2022 Correspondence to: Susanne Victor, susanne.victor @medsci.uu.se © 2022 The Author(s). Published by S. Karger AG, Basel Karger@karger.com www.karger.com/iaa DOI: 10.1159/000525960 Keywords Dander · Equ c 1 · Equ c 2 · Horse allergen · Horse breeds · Saliva Abstract Introduction: Horse allergens are less studied than allergens from other furry animals and these allergens must be evalu- ated to understand the complexity of allergy to horses. The aims of this study were to develop assays for the horse aller- gens Equ c 1 and Equ c 2 in dander and saliva and to deter- mine their levels in ten horse breeds. The study also included a comparison of these findings with previous results on the levels of Equ c 4 performed on the same study population. Method: The study population included 170 horses from 10 horse breeds including American Curly and Russian Bashkir horse, which have been suggested to be hypoallergenic. Competitive ELISA assays were developed, with polyclonal antibodies as capture antibodies, for the detection of Equ c 1 and Equ c 2 in dander and saliva samples. Results: The horse allergens Equ c 1 and Equ c 2 were found in all dander and saliva samples from the ten horse breeds. The GM level (ng/µg protein) of Equ c 1 in dander was 470 (range 129– 2,569) and in saliva samples, 40 (range 6–160). The GM level of Equ c 2 in dander was 138 (range 18–1,650) and in saliva samples, 0.8 (range 0.03–17). In dander, there were no sig- nificant differences in Equ c 1 and Equ c 2 GM levels between stallions, mares, and geldings. Conclusion: Our results show high intra- and inter-breed variability. Neither the American Curly horse nor the Russian Bashkir horse, earlier categorized as hypoallergenic breeds, was associated with lower aller- gen levels of Equ c 1, Equ c 2, or Equ c 4 than the other horse breeds investigated. © 2022 The Author(s). Published by S. Karger AG, Basel Introduction Equus caballus (domestic horse) continues to play a major role in human history although its use has changed greatly over the years and has included the development of a large number of breeds. Allergy to horse has been re- ported to affect up to approximately 14%, in a study from the north of Sweden [1], but horse allergy and horse al- lergens are less studied than allergens from domestic fur- Edited by: O. Palomares, Madrid. is is an Open Access article licensed under the Creative Commons Attribution-NonCommercial-4.0 International License (CC BY-NC) (http://www.karger.com/Services/OpenAccessLicense), applicable to the online version of the article only. Usage and distribution for com- mercial purposes requires written permission.