For all their power, strength, and general magnificence, horses can be extremely delicate creatures. Among the many ailments to which they’re susceptible, horses can suffer from seasonal allergies—yes, just like us! In fact, it’s estimated that 10% of horses suffer from seasonal allergies.1
If you notice your horse showing certain symptoms or unusual behaviors during the warmer months, things that can’t be explained by a virus, and don’t seem to be going away, equine allergies might just be the culprit.
But how can you be sure? How can you identify the allergen responsible? And, most importantly, what should you do about this horse health condition?
Read on for an in-depth beginner’s guide to allergies in horses.
Understanding Allergies in Horses
An allergic reaction is an overreaction of the immune system to an otherwise harmless substance.
The immune system normally guards against intruders like bacteria and viruses, but in both people and horses with allergies, the system is overly vigilant. It misidentifies an allergen—like pollen, mold, or dust—as a serious threat, and releases chemicals called histamines.
Histamines cause those symptoms that may be familiar to you: itching, sneezing, coughing, redness, inflammation, and more.2
As human and horse allergies share the same underlying science, allergies in horses can present in some of the same ways as in humans. However, there are several other symptoms that present quite differently. (More on that in a minute.)
Potential Causes and Common Allergens
Horses can have an allergic reaction to a substance the first time they encounter it, or develop a sudden allergy to something they’ve been around for years with no issue.
There are some indications that equine allergies are caused by a horse’s genes, but there isn’t yet a consensus among scientists.1
Common Horse Allergens
Many substances around a barn can be a horse allergen and trigger a horse’s seasonal allergies, including:
- Tree and plant pollens
- Sap of native trees
- Mold
- Dust
- Insect bites
- Seasonally-applied topical medications and repellents
Your local veterinarian should be familiar with native flora, allergens, and irritants when it comes to horse care. So when you’re on the hunt for the horse allergen your horse is battling, turn to your experts for a second set of eyes.
The Signs and Symptoms of Allergies in Horses
What can seasonal allergies look like in your horse?
There are two categories into which equine allergies mainly fall: respiratory and dermatological.
Respiratory Symptoms
Have you ever gotten sneezy when the trees begin to bud, or couldn’t stop coughing at that time of year when pollen coats your car?
Horses experience much the same as us when we have a pollen allergy. Their respiratory allergy symptoms can include:
- Runny nose – Gloopy, often yellow or green-tinted mucus can be seen gathering in the nostrils.
- Sneezing and coughing – A horse’s cough is quite different from ours,3 but all owners should be able to recognize its distinctive sound.
- Weepy or goopy eyes – If its eyes become irritated, your horse may suffer from mucous discharge from the tear ducts.
- Exercise intolerance – Often the first sign that your horse is in some kind of distress, exercise intolerance can stem from a few sources, including reduced lung capacity from seasonal allergies.
- “Heaves” – Recurrent Airway Obstruction, known colloquially as “heaves,” is a more severe accumulation of pus and mucus in a horse’s airway. RAO cannot be cured, but it can be managed if caught early.
These symptoms can range from mild to severe, the latter requiring urgent veterinary intervention. If you’re in any doubt, you should always check in with your vet.
Dermatological Symptoms
An allergic reaction in a horse can also affect its skin, and in turn, its coat. Horse allergy symptoms of the skin can include:
- Atopic dermatitis – This type of horse dermatitis refers to the classic itching, irritation, and hives of an allergic reaction.4
- Hair loss – Your horse may lose patches of hair due to itching and scratching against available surfaces.
- Secondary infections – In severe cases, affected areas of the skin can become infected and weepy.
One of the most common seasonal allergic disorders in horses, “sweet itch,” has been the bane of farmers’ existence for decades, and though it is a dermatological condition, it sits in a category all its own.
Sweet Itch
Sweet itch, also known as Queensland itch, is a kind of skin condition brought on specifically by culicoides midges (sometimes referred to as “no-see-ums” or biting midges). It’s an extremely uncomfortable condition for horses, bringing on large hives or welts, inflammation and redness, loss of hair, and infection.
Unfortunately, it’s also one of the most common seasonal allergies in horses.
You may notice the symptoms are similar to those of typical atopic dermatitis. It is the prolonged and treatment-resistant nature of the condition that makes it stand out.
While there’s some evidence that topical medications provide temporary relief when treating sweet itch, the best way to manage the symptoms of sweet itch is to keep your horse inside during peak insect hours, fill your stable with flypaper, and consider covering your horse in a fly sheet.6
The Science of Sweet Itch
When biting midges feed on a horse, their saliva enters the bite wounds they’ve created. Many horses will have only a minor irritation reaction.
However, some horses with insect bite hypersensitivity experience a more severe, prolonged allergic reaction to the midges’ saliva—there’s some evidence that it may be a genetic predisposition. It’s this group of horses who suffer from an ongoing and constant allergic reaction, one that can easily continue for the duration of the warmer months, or even beyond.5
Identifying and Testing for Allergies
Diagnosing seasonal allergies in a horse can be tricky. There are many diseases and conditions that it’s important to rule out first.
Before you settle on allergies as the source of your horse’s symptoms, you should ensure that it isn’t suffering from:
- A viral infection
- A fungal infection
- A bacterial infection (one that has caused scratching behavior, and wasn’t caused by scratching behavior)
A veterinarian can help you get to the bottom of your horse’s symptoms with the appropriate tests. Once the results for viral, fungal, and bacterial infections have come back negative, you’ll move to allergy testing.
Allergy Testing in Horses
Once-favored blood testing has lost the support of the scientific community.6 Here are the allergy test methods currently recommended.
Elimination Method
The first step for many owners is to eliminate various potential allergens, one at a time, from their horse’s environment. Through trial and error, you may be lucky enough to find the offending substance without taking a trip to the vet.
This method is especially promising for owners who recently introduced something new to their horse’s environment, like a new fly repellent for the summer.
If, however, your horse’s symptoms are severe, it’s best to get to a veterinarian as soon as possible.
Skin Testing
The best way to get a comprehensive look at your horse’s particular sensitivities is to get skin testing done. This testing is similar to what humans are given.
You can expect something along these lines:
- A patch of hair will be shaved off your horse, most likely around the neck.
- A cluster of small needles will be simultaneously injected just under the skin, each needle holding the essence of a different allergen.
- Your horse will be monitored for 24 hours.
If an injection site flares red or swells up during the monitoring period, your horse is likely to be allergic to the substance that was injected by that needle.
At this point in time, allergy testing in horses may be more susceptible to false positives than human testing. You may want to ask your veterinarian about this when discussing the results of any test.7
How to Treat Your Horse’s Allergies
Once you’ve established that your horse’s symptoms—be they respiratory or dermatological—are stemming from an allergic reaction, you can get down to soothing them.
There are a few allergy treatment routes equine health professionals recommend.
Medication
Antihistamines and, if necessary, corticosteroids are a common place to start. Steroids are used to suppress the overactive immune system, while antihistamines are used to suppress the release of those itch-inducing chemicals.
A topical medication may reduce itching, redness, and inflammation when applied to affected patches of skin. Oral medication, as it travels through the bloodstream, can also target multiple issues in different areas of the body.
Always consult your veterinarian before treating your horse with any kind of medication.
Allergy Shots
If your veterinarian has found overwhelming evidence of a specific allergy, they may recommend desensitization through regular injections. It typically takes a year before these injections take effect. Allergy shots may be recommended for horses with dermatological reactions, but are less often used for respiratory ones.8
Hygiene
Keeping up your horse’s hygiene during your local allergy season can keep allergens at bay. Medicated soaps, horse shampoos, and other products can be especially useful in keeping your horse’s skin, nose, and throat free of allergens that may lead to a reaction.
Medicated equine shampoo such as our Vetericyn FoamCare Equine Medicated Shampoo can keep your horse’s skin and fur clean and healthy. It’s also designed with a hypoallergenic and anti-inflammatory formula.
Additionally, support your horse’s eye health with an antimicrobial eye wash like our Vetericyn Plus® Antimicrobial Eye Care Kit. The gentle eye wash and gel are designed to clear your horse’s eyes of debris and elements from the air.
Send Equine Allergies Packing
When you start to sniffle in the springtime, you may not be alone—your horse might be sniffling because of the exact same tree pollen!
If you notice your horse scratching, sneezing, or coughing, consider eliminating variables from its environment one at a time. If this doesn’t seem to help, or their symptoms worsen, we recommend you speak with your veterinarian.
For over a decade, Vetericyn has been committed to advancing animal wellness. Be it your backyard farm animals or the furry friends inside your house, we offer cutting-edge solutions to further your animal companion’s health and happiness.
Reviewed by Solomon Benarroch, Veterinarian
Solomon Benarroch DVM has been a practicing veterinarian for over 30 years. His primary focus has been in equine soundness and performance sports medicine. Originally from Winnipeg, Canada he attended college at the Western College of Veterinarian Medicine. And completed an internship at the University of Minnesota. He is the father of three kids and when he isn’t working (which is rare), he enjoys traveling, cooking, and spending time with friends and family.
Sources:
- Dressage Today. Investigating Seasonal Equine Allergies. https://dressagetoday.com/horse-health/seasonal-equine-allergies-27897/
- Penn Medicine. What Are Allergies? https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/allergies
- Farr and Pursey Equine Veterinary Services Ltd. Horse Cough. https://www.youtube.com/watch?v=-jcBFqcdpuI
- The Horse. Atopic Dermatitis in Horses. https://thehorse.com/112585/atopic-dermatitis-in-horses/
- Medical and Veterinary Entomology (Third Edition). Biting Midges (Ceratogoponidae). https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/sweet-itch
- Equine Veterinary Journal. A commercially available immunoglobulin E-based test for food allergy gives inconsistent results in healthy ponies. https://pubmed.ncbi.nlm.nih.gov/25290573/
- Vet Dermatology. Discrepancies in the bilateral intradermal test and serum tests in atopic horses. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589420/
- Steinbeck Peninsula Equine Clinics. Equine Allergies. https://www.steinbeckpeninsulaequine.com/post/equine-allergies
