We are used to hearing about people who are allergic to cats and dogs but possibly less familiar with hearing about people who are allergic to horses. Perhaps 15 years ago Horse and Hound ran an April Fool’s day spoof suggesting that children would have to wear gloves and masks due to hew health and safety regulations and the risk of becoming allergic.
In 2003 a study by the AHT and Bristol University (Preedy, Franklin, Kendrick and Marlin) to determine the incidence of work-related symptoms in people working professionally with horses was presented at the American Thoracic Society conference. This study found that although 40 % of workers reported no symptoms, 17 % of workers did report occupationally related symptoms of wheeze, cough, shortness of breath and rhinitis, which were reduced or disappeared when away from the working environment.
A recent larger study in 110 subjects backs this up (Ketencioglu et al. 2020). They studied 80 people working on horse farms in Turkey and a control group of 30 people who had no known interaction with horses. Atopy (the tendency to develop an exaggerated immune response to allergens) was more common in the horse farm workers (41%) than the healthy subjects (13%). Sensitisation to horse allergens was found in 10% of the horse farm workers but not in any of the control subjects. FEV1 ratio (an indication of lung function) was lower in the horse farm workers (89%) than in the healthy control subjects (104%).
So, in the same way that we can be allergic to pollen or moulds or dust mites, people can become allergic to horses. This allergy is primarily to “dander” – fine broken material from the skin and hair and to sweat protein (latherin).
The authors concluded that “These results once again reveal the relationship between the intensity of specific allergen exposure and the sensitization to this specific allergen”. They also made the suggestion that, given that atopy has a genetic component, that “before employment, evaluation of atopy for professions involving potential exposure to occupational allergens with high immunogenicity can be instructive in terms of profession selection.” Essentially, people should be screened before employment.
References
Baran Ketencioğlu B, Yilmaz I, Tutar N, Gülmez I, Oymak FS. Horse allergen sensitivity and respiratory symptoms among horse farm workers [published online ahead of print, 2020 May 12]. Turk J Med Sci. 2020;10.3906/sag-1912-39. doi:10.3906/sag-1912-39