Equine Allergies and the Immune System

I remember, as a child taking riding lessons, getting started at the trot and the horse coughing a few times.  I remember feeling like he was going to pull me right over his head and being worried something was wrong.  My instructor would say something like, “He’s just cleaning out the cobwebs.”  The cough would stop and my lesson would go on.

Many times, the cough at the beginning of a ride is to clear out mucus or debris, ie. “clean out the cobwebs.”  But, if the cough persists it could be caused by swelling in the respiratory tract.  If you also notice trouble breathing, shortness of breath or lack of energy, a vet evaluation is recommended.

Recurrent Airway Obstruction (RAO) also known as heaves and is sometimes now referred to as equine asthma, consists of narrowing of the airway, mucus production and bronchial spasm.  With RAO, breathing is not normal at rest, breathing is labored, respiratory rate is increased and a cough is often present.  It can also be characterized by chronic cough, nasal discharge and exercise intolerance while the most severe cases will lose weight and often will go off their feed.

Two types of RAO exist, barn-associated and summer pasture-associated obstructive pulmonary disease, more commonly known as summer heaves.  Both types are due to the lungs hypersensitivity of an inhaled antigen, most often mold, organic dust and/or endotoxins in hay and straw.  This hypersensitivity is what we know as allergies.

I continue to be intrigued by what an allergy actually is and how an issue in the gastrointestinal tract can influence allergies.  We often assume that the antigen is harmful but it is the body’s immune response that is more harmful and damaging.  For some reason, the body develops an immune response to an otherwise not harmful antigen.  This immune response is due to the immune system not working properly as a result of swelling being present in the body.  Once swelling is triggered, the body’s immune response is affected and unable to work properly.  Swelling within the body directly impacts many other functions of the body as well and alters cell function causing the body to not have the ability to fight off disease.  Most often, when swelling is present in the respiratory tract there is an issue in the gastrointestinal tract.  Many factors can contribute to dysfunction in the GI tract such as genetics, stress, diet and nutrition and medications.  The body then mounts an immune response to the GI tract dysfunction and swelling which over time is damaging to the body itself.  The immune response becomes over reactive causing the body to be sensitive to otherwise not harmful antigens.

What can YOU do?

We always recommend a vet evaluation when you have concerns about your horse.  Once it is determined that the cause is allergies, there are many things you can do to improve their condition and manage symptoms.  Steps to manage the environment and diet should be taken first.  Horses with barn-associated RAO should be on full-time turnout or as much as possible.  If the horse must be in a stall for any amount of time it is important that the stall is well ventilated, hay is not stored above the stall, there is no sweeping or stirring up dust around the stall and low dust bedding should be used.  For horses with pasture-associated RAO it is recommended to reduce or avoid access to pasture except during winter months.  Wetting hay, using low dust hay or all pelleted feed is recommended.  If feeding hay, hay should be fed on the ground or hung in hay nets below nose level to prevent debris falling into nostrils.  If the horse is in a flair up or recovering from one, exercise in winter months should be minimized as cold air can aggravate the inflammation of the airway.  In some cases, your veterinarian may recommend medication.  It is important to remember that medication will treat the symptoms but once the medication is discontinued, symptoms will return if the environment has not been managed to reduce the presence of allergens.

Promoting a healthier body in general is also an important step in improving your horses condition.  Feeding quality forage, as horses were intended to eat, will help to get them the nutrients they need to have a healthy gut.  Horses need high fiber, low starch forage to keep their digestive system constantly working and everything moving.  Feeding whole, natural grains free of fillers, synthetics and sweeteners contribute to a healthy body which leads to reduced swelling within the body and a rebalanced immune response.  A healthy gut can be promoted by using a natural supplement that contributes to healthy bacteria and flora in the gut that keeps the balance there in check.

It is important to remember that the swelling and negative effects on the immune system have likely been occurring for a long period of time and therefore may take more time than you would hope to repair it.  While many allergies are seasonal and flair ups only occur during certain times of year when the allergen is present, the problem is still there year round.  Symptoms may not be present but it is important to maintain the regimen to reduce the effects year around, because symptoms will return and at times will be worse, if you don’t.

If your horse suffers from allergies you may be interested in these Emerald Valley products:

For gut health:

Quality forage:

Support normal inflammatory response and soothe and support your horse’s airways:




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