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What is Barley Allergy?

Horses can develop allergies to any food, and barley is no exception. Food allergies can cause hair loss, itching, and swelling, along with scaly skin and lesions. An allergy is the immune system of the body responding to a perceived threat, in this case, the barley present in the diet of the horse. In order to reliably determine which allergen is affection your equine, an elimination diet may be recommended. This can be time-consuming but may be required in order to deduce which ingredient is causing the reaction.

A food allergy is an over-reaction of your horse’s immune system to a particular ingredient of their diet. Allergies to food, such as barley, can cause uncomfortable and unsightly skin disorders and infections.

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Symptoms of Barley Allergy in Horses

Symptoms of food allergies rarely involve as many signs of gastrointestinal distress as food intolerance, but instead manifest with the following symptoms: 

  • Bloody or runny nose
  • Discharge from eyes
  • Hair loss
  • Hives
  • Itchy skin
  • Lesions and abrasions from itching
  • Reddened skin
  • Regional swelling
  • Scaly skin
  • Swelling of the shoulders or belly

Types

  • Food Allergy - A food allergy is a response initiated by the body’s immune system to protect itself against a perceived threat; an allergic reaction will not happen the first time an equine is exposed to the allergen but instead is triggered by repeated exposures
  • Food Intolerance -  Food allergies is the body’s immune system reacting to what it perceives as a threat, food intolerance, however, has no immune involvement; an intolerance to a food type is more likely to cause a gastrointestinal response than allergies do (additional symptoms, such as gurgling sounds coming from the GI tract and a change in the consistency or color of the stools)

Causes of Barley Allergy in Horses

Allergies, including food allergies, are caused by an abnormally powerful defensive response to a protein that has been identified as an invasive substance to the immune system. It is estimated that around 60-70% of our immune system cells actually reside in the digestive system, and the same applies to our equines. The process of digestion is designed to break down our foods into their smallest parts, called amino acids.

These amino acids are then broken down by white blood cells called Enterocytes and absorbed into the bloodstream. When these proteins are not properly broken down during the digestive process, enterocytes view them as intruders and attack. Over time the response of the immune system becomes more aggressive, and symptoms intensify.

Diagnosis of Barley Allergy in Horses

The symptoms of allergy are relatively non-specific and may indicate a number of different diseases or disorders. The signs that your horse will be showing due to a food allergy will also prompt your veterinarian to perform a complete physical examination, including standard blood tests and the collection of skin scrapings from any affected areas in order to carry out a cutaneous cytology. Cutaneous cytology is the microscopic assessment of the skin cells to look for problems like yeast infections, mites, or signs of disease. When these are not found on the surface of the skin, then a food allergy may be suspected. Although both serum and intradermal testing are available for the detection of allergies in equines, these tests both tend to be unreliable when attempting to diagnose allergies related to food.

The gold standard for diagnosis of food allergies is the the challenge diet or elimination diet. This diet consists of feeding the horse one protein source and one carbohydrate source that the animal has not been introduced to previously, and is continued for four to six weeks. If the elimination diet is successful, additional foods may be added into the diet of the horse gradually. Any dietary changes for horses need to occur gradually in order to avoid colic and other gastrointestinal upsets.

Treatment of Barley Allergy in Horses

It can take several weeks for a challenge diet to reveal the offending allergen, and during this time your horse may continue to experience symptoms. Corticosteroids may be recommended to reduce swelling and antihistamines may be utilized to calm the itching. Use of these treatments may mask allergic symptoms, making it harder to determine which ingredient in your horse’s diet is causing the reactions, so some equine doctors prefer to complete the elimination diet before applying additional medications. Secondary skin infections frequently develop alongside food allergies in animals, and antibiotics may be prescribed to combat this problem.

Once the dietary allergen has been identified, the initial course of action is avoidance of the ingredient. As barley is typically given in feed, rather than a plant that is sampled in the field, removing the ingredient from the horse's diet should clear up the symptoms. In the case of sport and performance horses, the nutritional needs for performance may not be adequately met by a challenge diet and these activities may need to be halted for the duration of the testing.

Recovery of Barley Allergy in Horses

In order to prevent reactions to accidental exposures to barley, equines may be further treated with immunotherapy. Immunotherapy for horses can take the form of either injections or drops, and it is formulated with small amounts of the allergen in order to desensitize the animal. The compounds that are found in the shots or drops that are given to the animal are specially formulated for the animal to be treated and typically require administration on a frequent basis for several weeks to months before the body is desensitized to the proteins found in the barely. It may take six months to a year before the benefits of immunotherapy are realized.