Allergy in horses : 7 facts you should know

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Pollen, food or house dust – more and more people suffer from allergies. And our four-footed partners also react sensitively to environmental influences. Therefore, we have  collected seven important facts about allergies in horses for you.

The immune system is our bulwark against pathogens. But in some people, this defense becomes unbalanced. The result: Actually harmless substances such as pollen or house dust are classified as attackers. The immune system then goes on the defensive.

And this overreaction also occurs in horses. This means that your immune system can also react too strongly to actually harmless substances. Because even if there are no reliable figures, experts assume that more and more horses have allergies.

Research has shown that the horse’s immune system reacts in a similar way to our human defenses. However, there is one big difference: While allergies often accompany people throughout their lives, in some cases an allergy in a horse can completely regress.

1. There are many triggers

As with humans, there are many potential triggers for allergies in horses. In other words, almost any substance can theoretically trigger an allergy. Because the substance is not the problem, but the “hysterical” immune system. For example, it can react to pollen, mold, dust, parasites, insects, storage mites or medication.

By the way: Horses can also be allergic to animal hair, such as dog hair.

One of the well-known allergies in horses is the food allergy. An international study with researchers led by Erika Jensen-Jarolim from MedUni Vienna’s Institute of Pathophysiology and Allergy Research found that horses react particularly well to buckwheat, but also to alder pollen and Bermuda grass, also known as “dog tooth grass”.

“Buckwheat, as a protein-rich pseudocereal, is very often found in horse goodies and horse muesli,” explains Jensen-Jarolim. “The reaction to pollen from the flat-growing Bermuda grass of all things can be explained by the fact that horses have their noses low to the ground when they are grazing.”


The most common allergies in horses are:

  • Insect allergy, including summer eczema , for example . It has been proven that sweet itch is mainly caused by one species of mosquito
  • Environmental allergy or atopic dermatitis. This is where the horse’s immune system reacts to allergens such as pollen from trees, grasses, herbs, house dust mites, storage mites and mold
  • Contact allergy, which usually shows up in connection with the saddle or the saddlecloth
  • drug allergy

2. It’s also in the genes

The following applies to humans: If one parent is allergic, the risk for the child to also develop allergies is around 30%. If the father and mother are allergic, this probability rises to over 60%. Exact figures are not available for horses, but one thing is certain: the predisposition to an allergy can also be inherited in them.

According to a study from the USA, the following horse breeds are particularly at risk: Morgans, Swedish Warmbloods, Oldenburg horses, Hackney horses, Paso Finos and Arabians. In addition, male horses are almost twice as likely to have atopy as mares.

3. Typical symptoms are coughing and wheals

As with us humans, an allergy can also show up in horses through different symptoms. In most cases, it is chronic, meaning it keeps coming back. However, some horses react immediately to allergens. Then it can come to the so-called anaphylactic shock: The horse has shortness of breath, severe skin wheals, even a circulatory shock is possible.


Typical symptoms of an allergy are primarily respiratory problems such as coughing. The eyes of allergic horses often water constantly or develop a sticky, rather solid secretion.

An allergy can also be visible on the skin. Then wheals and pustules form over a large area or all over the body, which can even fill with pus. A food allergy is shown, for example, by severe diarrhoea, watery faeces and gas build-up. However, gas or cramping colic can also occur.

4. A blood test helps with the diagnosis

Finding the trigger is often real detective work. The examination usually begins with a process of elimination: If other causes of the disease are not possible, the allergen is sought.

For this, the veterinarian asks about factors such as housing or feeding. When the symptoms appear is also important. It can help if you keep an allergy diary, i.e. write down when the symptoms appear. For example only after a ride that leads past certain plants? Or if the hay is dusty? Just one season? Or when the surrounding fields are being sprayed?

Allergy tests also help with the diagnosis. To do this, the veterinarian injects the allergy-causing substances in small quantities under the horse’s skin. Based on the skin reaction, he can tell whether an allergy is present. Another way to diagnose allergies is to have a blood test, which measures the level of antibodies to allergens in the blood.

5. Treatment means avoidance

The symptoms are often treated with medication, including essential fatty acids, antihistamines or cortisone. A specific immunotherapy, the hyposensitization, is also possible. For this purpose, a hyposensitization solution for the horse is prepared in the laboratory based on the allergens determined in the blood. Then the horse is exposed to the allergens with increasing concentrations – this is how the body should slowly get used to the allergens.


However, the best treatment for horses is to avoid the allergenic substances. For example, the vet changes the feeding or he recommends a more dust-free housing. However, with some allergies, such as pollen allergy, complete avoidance is very difficult.

6. Strengthen the gut

Experts say most allergies in horses originate in the gut. Along with the liver, the intestine is also the central organ in the metabolism and the control center of the immune system in horses.

To strengthen the intestines, you should feed good quality hay that provides raw fiber for healthy digestion. Avoid haylage and silage – they acidify the intestinal environment and damage the intestinal flora.

milk thistle

Herbs can also help: milk thistle and fennel, for example, have a beneficial effect on intestinal cleansing and digestive processes. In addition, these plants strengthen the liver function and metabolism. Yarrow supports the intestinal mucosa through the bitter substances it contains and strengthens the development of microorganisms in the intestine.

7. Prevent allergies

Of course, prevention is also the best remedy for allergies – but it is not that easy. Basically, you can optimize the posture of your horse. This means that you pay attention to a good feed quality. Because dusty hay or feed containing mold can cause a feed allergy in the horse.


A clean stable with low-dust bedding and good air also helps your horse. Steaming the hay can help with dust, mite and pollen allergies. Regular treatment against parasites and insects is good for this.

Horses with summer eczema often need an eczema blanket to protect against the bites of midges and black flies. In addition, the horses should always have the opportunity to retreat to a dark and cool stable.


In summary, the following measures have proven effective for horses with allergies or a tendency towards allergies:

  • Only use feed of the best hygienic quality
  • Comprehensive supply of minerals, vitamins and trace elements
  • Strengthen bowel function and keep it intact
  • Strengthen horse immune system
  • Reduce and avoid stress


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