And The Vet Said...

Allergies

R. Dean Meyer DVM
Lodi Veterinary Hospital and Madison Equine Clinic

As the show season begins to slow and kids return to school it is a time to reflect back on the crazy spring and summer we just finished in a busy equine practice. This is the time of year I like to review my previous cases and look for trends or common conditions I have treated. I have definitely noticed an increase in allergic reactions in horses. This includes both skin reactions, such as hives, and also respiratory reactions including COPD, "heaves". I am not sure if this is due to management practices, an increase in stress or just coincidence but as with many conditions in the horse, prevention by management changes can go a long way in future outbreaks.

The most common treatment for allergic reactions in the horse is Dexamethasone. Dexamethasone is a synthetic corticosteroid. Coricosteroids are important in normal protein, carbohydrate, and fat metabolism. They are also important for controlling inflammation. Dexamethasone is very effective but has definite negative side effects if not used properly.

Adverse effects due to corticosteroid treatment usually occur with long-term use of the drug. These adverse effects can include suppression of the immune system, gastric ulcers, problems with the skeletal system, or even laminitis.

Because of these detrimental effects you need to keep in very close contact with your veterinarian when using these drugs on your own. When they are used properly and for short periods of time they can be of definite benefit, but when used improperly or long term, adverse effects can arise.

Just like allergies in humans, it can be difficult to diagnose allergies in a horse. They can exhibit many different signs from coughing to raised welts, to runny eyes. Additionally allergies can take years to fully develop. A horse that has never been allergic to something in the past can suddenly develop an allergy without warning.

Skin allergies are some of the most common allergies seen in horses. They generally appear as hives around the neck or shoulder area. They can be caused by food, bedding, something inhaled or even insect bites.

Respiratory allergies generally appear as coughing, or nasal discharge. Chronic Obstructive Pulmonary Disease (COPD) or heaves is the term most often used with this allergy. Pollen, dust or mold is the most common culprit in this condition.

As mentioned earlier prevention is the best method of control for allergies. Horses that have a history of allergies may benefit from allergy testing to determine what exactly it is they are allergic to. Common management practices can include fly sheets for horses with insect allergies. Some horses also have been shown to be allergic to Molasses in feed stuffs, so eliminating this may be of benefit. Those with COPD will benefit from having their hay source soaked in water to remove any dust, or perhaps switching to hay cubes. These horses also benefit from being kept out of doors in well ventilated areas to prevent exposure to mold spores and dust.

Boosting the immune system by feeding a good quality organic mineral has also been known to help prevent some future allergic outbreaks. Feeding a probiotic, extra anti-oxidants such as Vitamin E or C can also help these animals. There has also been some evidence that feeding omega fatty acids may help in some cases.

The importance with allergic horses is to try to prevent any future occurrences and keep in very close contact with your veterinarian when using corticosteroids, such as Dexamethasone.