Are some horses hypoallergenic?

So far research doesn't support claims that curly-coated horses are less likely to trigger allergic reactions in people.

A German study challenges the theory that American Bashkir Curly Horses are less likely than other breeds to trigger allergic reactions in people.

Bashkir Curly Horses have long been reputed to be less allergenic than other types of horses, but science has yet to confirm that.

People unfortunate enough to have an allergy to horses experience many of the same symptoms as seasonal allergy sufferers. “The clinical presentation is variable but most people react to horse allergens with the typical symptoms of hay fever, including sneezing, a runny, itchy or stuffy nose and itchy, burning and watery eyes,” says Eva Zahradnik, MSc, of the Institute of the Ruhr-University Bochum. “In more severe cases, horse allergy can manifest as asthma, including wheezing, coughing, chest tightness and shortness of breath. Reactions of the skin (hives) are also possible but less common than respiratory symptoms.”

Curly Horses have long been reputed to be less allergenic than other types of horses. “This hypothesis is mostly based on experiences of persons allergic to horses,” says Zahradnik. “Several websites, newspaper articles and TV segments report stories of horse-allergic individuals who can handle Curly Horses without suffering any allergic reactions.” Preliminary research seemed to confirm these observations, but the reason for the low-allergenic potential of Curly Horses was unclear, which led Zahradnik to devise a new study to test the premise.

Zahradnik’s team collected 224 hair samples from 32 different equine breeds. They alsoused personal nasal filters to collect dust inhaled by people grooming both Quarter Horses and Curly Horses. They then analyzed all the samples using a new immunoassay that detects the major equine allergen, Equ c 1, and a commercial immunoassay for the minor allergen, Equ c 4.

“Equ c 1, which is found in horse dander, saliva and urine, belongs to the lipocalin family of proteins and is primarily considered to be a carrier of odorants and pheromones,” explains Zahradnik. “Equ c 4 is a major component of horse sweat and it acts like a detergent, causing foam formation on the coat of sweating horses, especially where rubbing occurs. Both proteins are identified as allergens, which are substances that bind to the antibodies [immunoglobulin E (IgE)] responsible for allergic reactions in susceptible individuals.”

The researchers found that—contrary to popular belief—the dander and hair from Curly Horses contained as many allergens as those from horses of other breeds. In fact, the Curly Horses used in this study had higher levels of allergens than horses of other breeds. “The so-called hypoallergenic Curly Horses that we tested in our study had significantly higher allergen levels in hair than the majority of other investigated breeds,” says Zahradnik. “Based on our original assumption, these results were paradoxical, but not entirely unexpected. Similar results have been previously published for dog breeds. Significantly higher concentrations of dog allergen Can f 1 were found in hair of ‘hypoallergenic’ dogs, like the Labradoodle or Poodle, than of ‘non-hypoallergenic’ dogs like the Labrador Retriever. The concept of a hypoallergenic animal is still not supported by scientific evidence.”

Instead of differences between breeds, the researchers discovered a wide variation in allergen concentrations among individuals of the same breed. “These findings indicate that some animals might be classified as either high or low allergen producers within the same breed,” says Zahradnik. “This could be an explanation whysome allergic individuals only react to certain animals.”

The data also showed that stallions had higher concentrations of allergens than did mares or geldings, suggesting a link to hormones. “According to the scientific literature, the production of major allergens seems to be higher in male than in female animals, and in non-castrated than in castrated animals [in other species]. For example, castration of male cats significantly decreased levels of cat allergen Fel d 1, and injections of testosterone led to an increase in Fel d 1 production. However, this has not been specifically investigated in horses yet.”

Despite her study’s findings, Zahradnik says people with mild horse allergies may still want to see if they have less of a reaction to Curly Horses.

“From a medical point of view, the general recommendation for horse-allergic patients is to avoid further contact with horses. On the other hand, studies by our co-author have shown that horse-allergic patients suffer from milder or even no allergic symptoms when riding Curly Horses,” she says. “Despite our findings, we cannot exclude that a hypoallergenic effect really exists for this special breed. We only claim that the hypoallergenic properties of Curly Horses cannot be explained by lower allergen levels in hair compared to other horse breeds. In our opinion, it may be useful to check the effects of contact with Curly Horse if horse enthusiasts with only slight symptoms can-not or do not want to give up the horse contact.”

Reference: “Lower allergen levels in hypoallergenic Curly Horses? A comparison among breeds by measurements of horse allergens in hair and air samples,” PLOS One, December 2018

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