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One morning when you go to feed your horses and turn them out for the day, you notice your gelding appears to be wheezing. He happily eats his breakfast and is otherwise normal, so you turn him out anyway. When you bring him back in that night, he seems his normal self.
However, the next morning, he’s having trouble breathing again, and he has soft, flat, swollen lumps all over his body. The hives indicate an allergic reaction, and in hindsight, his wheezing the previous day was also a clue.
Deducing and treating allergies can be quite difficult. Where do you even start?
“Allergies are an interesting problem. Sometimes you’ll do the allergy test, and they’ll come up allergic for everything,” said Melyni Worth, Ph.D., P.A.S., of Foxden Equine, Stuarts Draft, Va. “It’s not possible to cure allergies; it’s an immune system problem.”
What Exactly Is An Allergy?
An allergy, by definition, is a hypersensitivity to one or more allergens, resulting in a markedly increased reactivity by the immune system after repeat exposures.
“People get really confused about the difference between an allergen and a bacterial response,” said Worth. “The bacterial infection you can fix. Allergies you cannot. Sometimes they come hand-in-hand, and you have to treat the bacteria first.”
Essentially, allergies are just an over-reactive immune system. If your horse has a healthy immune system, he will be able to handle all of the allergens present in the air and in the environment in which he lives. In general, equine allergies are either respiratory or skin related.
“The two primary complaints are either skin-related—skin lesions, lumps and bumps and itchy skin, or the other more common one is respiratory problems,” said Martin Furr, DVM, Ph.D., Diplomate ACVIM and Adelaide C. Riggs Chair in Equine Medicine at the Marion duPont Scott Equine Medical Center, Leesburg, Va. “The skin allergies, for the most part, are contact allergens; something is getting on the horse. The respiratory ones usually come from feed. As they’re eating, they inhale it, and they start to get breathing problems. That’s the more common one. In humans, they have intestinal allergies, and we haven’t really defined those really well, whether they occur or not.”
An allergy can decrease performance, be painful and unsightly, and can be expensive to diagnose and treat. Secondary issues such as self-trauma like tail rubbing can also become an issue.
Diagnosing An Allergy
The first step in diagnosing an allergy’s source requires two different tests.
In the intradermal skin test, the veterinarian will inject minute amounts of allergen in the skin and monitor the reactions over a 24-hour period.
Blood testing is much more prevalent and involves testing the blood with different allergens to see which ones cause a reaction.
Another way to diagnose allergies, especially feed-related issues, is to use a little deductive reasoning.
We look to see if there’s a common factor when the symptoms appear,” said Worth. “You work your way through logically until you narrow down the cause, then you eliminate those things from the diet and see if it goes away. You do your best, try to work your way to the problem, and see what the horse tolerates and doesn’t. It can be a real pain!”
Most Common Equine Allergens
- Insects
- Mold
- Grasses
- Tree Pollens
“From a digestive perspective, two-thirds of the immune system is housed in the walls of the gut,” said Joyce Harman, DVM, MRCVS, of the Harmany Equine Clinic in Flint Hill, Va. “The gut becomes extremely important in the immune system and allergies. If you’re putting food into the gut that the horse is sensitive to, you’re affecting the immune system.”
Tackling The Problem
Once you figure out the cause of the allergy, it’s essential to remove it from the horse’s environment.
“The cornerstone of treating allergies is to minimize exposure. You have to do all of the environmental management issues to minimize exposure,” said Furr. “The second thing is usually to treat with an immunosuppressant, minimize the reactivity and the response. That can be short term or longer term. Hopefully you identify what it is, use the drugs and get things quieted down so you can adjust the environment.”
Since dust and mold are major contributors to allergy-prone horses, one of the easiest ways to manage allergies is to keep the horse outside.
“It’s dusty and moldy inside, and the air circulation is less,” said Furr. “We want them out as much as possible. When it is inside, it needs to be in a stall that is well ventilated. Leave a window or something open, if possible. Make sure they’re not in a barn where hay is stored, especially in a loft over their head.”
As one can imagine, the problem with hay is that it is a professional dust collector. Bedding can also cause a dust problem.
You can spray down the hay with water, or dunk it, immerse it in water and let it get really saturated,” said Furr. “Change their bedding. There are low dust and dust free type beddings. Pine shavings tend to be lower dust than pine sawdust or straw. Don’t feed round bales outside. It can be moldy and moist, and they stick their heads right in the middle of it.”
