HomeExpert AdviceArticleAllergy or intolerance?

Allergy or intolerance?

Posted in Health and Veterinary

Does your horse react badly to changes in his diet? Perhaps he becomes spooky or excitable, suffers from loose droppings or even mild colic? Does he come up in unexplainable lumps and bumps? Or is his coat dull and scurfy?

Perhaps your horse suffers from one or more of these problems at the moment, but you just don’t seem to be able to get to the bottom of it? If this sounds familiar, it might be time you took a closer look at his diet.

Often when a reaction occurs, we tend to label it as an allergy, however feed allergies in horses are relatively rare, whereas intolerances to specific ingredients appear to be much more common.


Studies have shown that allergic reactions in man and other pets, such as cats and dogs, are very similar to those seen in horses. Allergies can take months or even years to fully develop and horses can suddenly develop allergies to certain ingredients even if they have never been allergic to them before.

A horse can exhibit many different symptoms when suffering from an allergy, which may vary from the horse appearing a little under the weather to raised lumps and bumps and swelling, particularly around the head.

Any horse may suffer from allergic reactions and the horses breed, age or gender do not appear to make him more susceptible.

But what is an allergic reaction?

To describe it simply, the allergen (whatever it may be) alerts an anti-body in the system called Immunoglobulin E (IgE). IgE is responsible for recognising invading bacteria and viruses in the body. It then attaches itself to these invaders and arouses the body’s defences (the immune system) to attack and destroy them. This can cause digestive upsets and other problems.

In cases of food allergy, the IgE antibodies appear to get their wires crossed and instead of attaching themselves to invading bacteria or viruses they attach themselves to perfectly harmless foods. This causes the immune system to react, producing reactions such as digestive upsets among others.

The immune system usually reacts very quickly and often quite dramatically which is why true allergies cause very swift and often violent reactions.

The root cause

From a medical point of view, and increasingly from a veterinary point of view, the true allergy is not difficult to diagnose, though the cause may be. Symptoms are likely to be obvious and immediate, and blood tests are available which will show whether a specific allergen causes an increase of IgE antibodies.

In veterinary medicine these tests are still not 100% reliable and may yield several false positives. As a secondary line of diagnosis, pricking the skin and inserting a small amount of the suspected allergen underneath the skin should also cause IgE antibodies to react very quickly if an allergy does exist. Your vet will also need to know about your horse’s history for example if there have been any changes to the diet or routine to help pinpoint the cause of the reaction.

Or is it an intolerance?

In humans, the awareness that food or specific food ingredients can cause health problems has risen dramatically over the last few years. However, it is now recognised in humans that there are several acute and chronic conditions that are affected, if not totally caused, by food (in that the patient’s body reacts in some negative way to food), but which are not caused by IgE antibodies sparking off an immune reaction. This does not mean to say that the immune system may not be involved in the process, but if so, it is through some mechanism other than an IgE antibody.

The same appears to be true for horses. The difficulty with this is that if IgE antibodies are not involved in the reaction, then diagnoses that depend on measuring the number of IgE antibodies produced by a certain food or feed are of no use.

Feeding allergy sufferers

Allen & Page have developed a Sugar & Cereal Intolerance Diet Sensitive souls – and tummies!

Many horses live quite happily with low-level sensitivities to foods that the owner may never even have been aware of, and which only become a problem when their health is compromised in some other way, such as through infection, stress, trauma or injury, or being generally run down.

The actual mechanism of how this happens is not clear. In humans there appears to be a genetic predisposition to such sensitivities and for example they may run in families.

Overdosing on a particular foodstuff can cause the body to react against it. It is interesting to note that nationally, food intolerance in humans tends to be highest to the food that the nationality eats in the greatest quantities. This may be why ingredients such as cereals (barley in particular) and molasses, which are widely used in horse feed for nutritionally sound reasons, are commonly suspected as sources of food intolerance.

If a horse has a feed intolerance, the culprit is commonly molasses, barley or sometimes alfalfa, but other cereals can be implicated. Feeds that contain cereal by products can also cause a reaction. A horse that has a feed intolerance may remain susceptible for many months or even its entire lifetime, although allergic bumps may disappear suddenly with the removal of the problem feed.

Is your horse suffering? Spot the signs

Signs of an intolerance are often skin-related, for example, itchy or scurfy skin or unexplained lumps or bumps, and may also include behavioural changes such as increased excitability or bolshiness. Other horses may show signs of digestive disturbances such as loose or watery droppings, or frequent bouts of colic.

Food intolerances may produce these problems and many more – they can affect the health of the horse in numerous ways. When intolerances build up it can then be difficult to eliminate them from the diet. Individual horses and ponies react differently to food intolerances.

Barley might cause one horse to get excitable, and give another a digestive upset. If the problem is not addressed, then eating foods that the body cannot digest and use properly will only stress the horse further and can lead to the number of foods that the horse reacts to increasing.

Feeding the whole horse

It is vitally important to consider the horse as a whole when dealing with intolerances.

Supplements may help relieve symptoms in the short term, but if a feed ingredient is causing a problem then how can your horse stay healthy?

It is like regularly taking painkillers for a headache, when what you should be doing is finding out what is causing the headache in the first place.

If you think your horse may have food intolerance remember that any of the above signs could have other non-feed related causes. Your first step should always be to contact your vet.

What should I feed a horse with an allergy or intolerance?

You would think that the answer to this is obvious – don’t feed the ingredient that the horse reacts badly to! And of course this is the answer, but it is not always that straightforward.

Of course, it is a good idea to check the list of ingredients on the feed bag, but don’t forget about other things that may be added to the diet such as chaffs and supplements.

Fortunately, there are now feeds on the market which cater for the horse that has a feed allergy or intolerance. These range from feeds which omit the most common causes of food allergies and intolerances through to feeds that are completely free from added sugars, molasses and cereals.

It’s possible to meet your horse’s dietary requirements without compromising his health by feeding an ingredient that he really can’t stomach.

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