Just like humans, horses can have a number of different types of allergies. The most common types of horse allergies are respiratory and skin. Rerpiratory allergies are also known as 'heaves' and are often similar to asthma in people. This article discusses the problem of horses being allergic, for information on people allergic to horses see Allergy to Horse.
A horse can be allergic to things in the air (e.g. pollen, dust, mold, spores), certain foods or nutritional supplements, or insect bites. Normally, allergies develop over time with exposure. For example, a horse may not have an allergy to straw but if exposed to moldy straw over a long period of time may develop an allergy to straw mold.
Just as people can have many different allergic symptoms (itchy eyes or skin, bumps or rashes, difficulty breathing), horses can have a variety of symptoms as well. Common symptoms in horses include:
Unfortunately, it can be difficult to diagnose an allergy, as each of these symptoms can have other causes, aside from allergies. For example, a throat infection could cause coughing, or a lung infection could result in breathing difficulty and reduced energy. Diagnosis is further complicated by the fact that there can be a delayed reaction between exposure and a visible reaction. For example, symptoms of skin allergies (e.g. bumps) may appear 12 hours after exposure to the allergen (the substance the horse is allergic to). Consequently, one may need veterinary assistance to determine if the symptoms are due to an allergy or some other cause. In some cases (particularly in the case of skin allergies) the veterinarian may take a tissue sample for analysis to determine if the problem is allergic and if so to help identify the cause.
Treatment and Prevention
The treatment of horses for allergies is similar to the treatment for people. The preferred treatment is avoidance. On exposure, there are a number of treatments (e.g. anti-histamines or corticosteroids) to reduce the symptoms and make the horse more comfortable. There are also a number of desensitizing treatments.
Alternatively, if the symptoms are not severe, one can separate the horse from the allergen and allow it to recover normally. If the horse is allergic to something in the stable (e.g. dust, fungus, mold) one can let it out to pasture until it has had time to recover and one has had time to clean the stable. Alternatively, if the problem is in the pasture (some plant), one can place the horse in a stable until it recovers.
Depending on what the horse is allergic to, some common solutions are:
Note that in the case of watered hay or straw, one must ensure that the hay and straw is changed daily so that it does not have time to develop mold or fungus.
Cleaning a stable tends to disturb dust, mold, fungus and other potential allergens. Consequently, one should always remove a horse from the stable while it is being cleaned and for some time afterwards (until things have had time to settle again).
Normally, a well ventilated stable will have fewer allergens than a poorly ventilated one. However, in the case of a dust allergy, increasing ventilation may make the situation worse (at least in the short term) as increased wind through the stable may stir up dust.