Allergies in horses – Symptoms, diagnosis, treatment

More and more horses come down with allergies.

Horses can exhibit a high variety of symptoms what makes the diagnosis quite difficult. Generally allergies are not curable. Horse owners can only try to improve their horses´ quality of life.

In the last decades the number of horses with allergies continuously increased.

The cause is easy to find: Originally horses lived in free nature and their fodder was nothing but fresh grass and herbals. Nowadays the domestic way of life does not consider these elements at all: Horses stay in the horse stable, do not move enough and breathe in a lot of dust and stink. The time on the pasture definitely is too short and the horses suffer from a lack of movement. The immune system cannot develop normally so that it is weak and easily gets infected by dust, the stink of ammonia and dry feed.
And the answer of the immune system: allergic reactions.

What is an allergic reaction?

An allergic reaction is an extreme defense reaction of the organism that is triggered by allergens. Every allergen offers a different chemical structure so that a general categorization is impossible. When allergens enter the horses´ body the organism reacts oversensitive and starts to produce antibodies. The defense cells begin to swell and the horse exhibits the first typical symptoms such as skin eruptions (wheals, sweet itch), respiratory problems and problems with the gastro-intestinal tract.

What causes allergies?

Every allergy is caused by environmental allergens. You can find allergens in:

Mites, pollen and molds (especially in fodder of bad quality)
Insects and parasites (black fly, mosquito, horse-fly and worms)
Chemical substances (wood and insect preservatives, color, medicine)
Grass and herbs (especially in stinging nettles on the pasture)

Additionally more and more horses show allergic reactions after intensive contact with sunlight and several pollutants of the environment.

Classification into respiratory allergies, skin allergies and feed allergies

Horses can show allergic reaction against many different allergens. Some horses only exhibit seasonal problems while other horses suffer all year long. In general it can be quite difficult for the horse owner to recognize the allergy. In some cases the allergens already are some days in the organism of the horse until you can see the first symptoms. Referring to this the diagnosis is very complex and can take quite a long time. The most serious allergic reaction is an anaphylaxis.

All allergies for horses have been categorized into three different types: respiratory allergy, skin allergy and feed allergy.

Symptoms of a respiratory allergy

Most commonly, horses suffer from a respiratory allergy. There are two different triggers for a disease of the airways: An infection via bacteria and virus or an allergic reaction of the interior mucous membranes after inhaling allergens. These allergens come from feed of low quality (hay, straw, silage, muesli and cereals) or dust air. At first the horse starts to cough. However, if your horse once coughs this does not need to be a hint for an allergic reaction. Horse owners need to be observant so that they can contact a vet as early as possible. A serious cough and chronic problems of the respiratory tract can lead to a chronic obstructive bronchitis or even heaves. Further symptoms are problems with breathing and nasal discharge. Cough, however, cannot be solved with suppressive medicine. Coughing is the only way that the horses´ organism gets free of the allergens. A respiratory disease is a serious disease and requires the correct treatment. Here you can find detailed information about the symptoms, treatment and prevention measurements of a respiratory disease.

Symptoms of a skin allergy

The skin is the biggest organ of the horse. It is the direct contact to the environment and reacts to external stimuli and influences. Skin allergies are triggered by insects, grasses and sunlight so that horses mainly suffer from them during the summer period. Horses can exhibit the allergy on different ways:

Wheals of all sizes pop up all over the skin (hives or urticaria)
The horse feels unwell, is nervous and tries to rub his itchy skin. This can cause sore lesions on the skin.
In the area of tail, croup, mane, ears and chin there are summer itches that look like sore points.
The horse can suffer from pinkeye.

Symptoms of a feed allergy

In case of a feed allergy the allergens enter the organism with the fodder. In the last decades the production of horse feed turned into an extremely complex process. With the help of synthetic processes certain fodder components (additives and concentrates) get conserved and stay useable for a long time. This clearly does not have much to do with the original fodder of the horses. The answer of the organism is an allergic reaction. Typical symptoms are diarrhea and impairing problems of the gastro-intestinal-tract. Some horses even suffer from a chronic form of colic. Clearly, the diagnosis and treatments of a feed allergy are the most difficult and time intense ones.

Headshaking

Headshaking can be triggered by an allergic reaction and is a serious disease for your horse. Here you can find all detailed information about the symptoms, diagnosis, prevention and treatment.

Diagnosis

Many symptoms can easily be associated with other equine diseases (e.g. colic, Equine herpes, worms). Especially respiratory diseases can be caused by other triggers such as parasites and insects. In case of a feed allergy it can take a very long time until you are finally able to determine the correct cause of the symptoms. Referring to this the diagnosis is very complex and can take quite a long time.

If your horse shows some of the symptoms described above the horse owner needs to contact a vet. First he will analyze the general living condition of the animal (husbandry, feed, etc.). In the next step he completely examines the horse and tries to define the correct cause. It can be very helpful for the vet if the horse owner is prepared for the following questions:

Does the horse exhibit the symptoms all year round or only seasonal?
Did the first symptoms exhibit after a general change of feed?
Does the health situation of the horse become better when it is on the pasture?

For the correct diagnosis the vet can choose between two different analysis techniques. The first one is the blood test. The vet takes blood samples of the horse and sends them to a specific laboratory. There, scientists find out if the blood offers any kinds of antibodies. The second option is an allergy test. The vet injects numerous tiny dosages of substances, each one with a different type of allergen. A positive reaction of the skin (swelling) shows you if the horse is allergic or not. In general you can say that the blood test is much more comfortable for the animal whereas the allergy test guarantees a more profound diagnosis.

Possible treatment

An allergy is a lifelong disease that is not curable. However, with the help of medicine and therapies the horse owner can achieve a significant improvement of the horses´ quality of life.

In case of an acute allergic shock the vet can prescribe medicine such as fatty acids, antihistamines and cortisones. These compounds have anti-inflammatory effects and cause a detumescence of the swollen organs.

The most effective treatment is an immunotherapy (hyposensibilization). This therapy can take up to several months or even some years and requires a great discipline of the horse owner. Veterinarians produce an individual solution made out of the antigens that cause an allergic reaction in the horse. The horse owner needs to inject this solution for several months. The detailed dates and dosages are explained in an individual schedule (the dosage continuously becomes higher). The organism is forced to face the foreign bodies and shall learn to tolerate them. In the course of the immunotherapy the horse can exhibit the normal symptoms. The therapy is quite promising (up to 70% of all therapies are successful) but it can take several months until the health situation of the horse becomes better. Horses that suffer from several different allergies sometimes even need to continue with the therapy until the rest of their life.

If your horse has a feed allergy you can try out a diet of exclusion. For a period of several weeks the horse owner only feeds one certain fodder component. If the horse does not exhibit the symptoms anymore you know that your horse is allergic against the fodder components you stopped to feed. The crosscheck is easy: Just start to feed the original fodder. If your horse exhibits the original symptoms your diagnosis is validated. The diet can only be effective if you do not only change the brand of the feed but also the fodder components (normally all brands use the same fodder components and only differentiate in the dosages). Moreover you need to avoid any kinds of treats. Most of them are made out of chemical additives so that they are often the trigger for an allergy.

Prevention measurements

The best prevention is the species-appropriate husbandry. Horses need light, fresh air, movement, a balanced feed (minerals, electrolytes, vitamins, fruits and vegetables) and a clean horse stable free of bacteria and parasites. This husbandry supports a healthy immune system and this indeed is the best prevention against any equine disease.

All feed products need to be of good quality and free of any mold and dust. Indeed, the preventative measurements against a grass, insect or sunlight allergy are limited. You can hardly influence the environment of your horse and if the horse shall not only stay in the stable all day you always need to find a compromise. The most effective prevention measurements are a regularly control of the pasture (the pasture needs to free of allergen grasses and especially stinging nettles). Additionally it is very helpful to use an equine fly mask (see picture). The horse is protected against insects, pollen and sun beams. In general you need to make sure that the pasture is free of any kind of chemical fertilizers and insect repellents.

All products of the daily feed and cleaning processes need to be free of chemical substances. Instead, horse owners can make use of natural products. To give some examples: In case of an injury or disease the horse owner can try to use grasses and medicinal plants. Moreover he can use neem oil products for the daily coat care and in summer as a prevention against insects and parasites (here you can find all information about neem oil products).

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—All statements without guarantee—