The Stables

The Biochemistry of Itch

Imagine my joy when I arrived to ride my horse last summer and was confronted with this!  I had recently moved him to my sister’s paddock to take advantage of the grass and ample space. Little did I know, all of this came with an unwanted added extra – something he was allergic to.

What caused this?

The cause of skin allergies in horses is often notoriously difficult to pinpoint – it could be dust, mould, pollen, insect bites (especially Culicoides), chemicals, food, material, vaccines or drugs.

Your vet will likely do a physical examination and make an intelligent guess based on the nature and location of the symptoms, your horse’s surroundings, the time of year and various other factors. If you need a more accurate diagnosis, he might do a microscopic evaluation, a serum allergy test or intradermal skin allergy testing.

What is actually happening in your horse’s body to cause this? The immune system works like an army during a foreign invasion. First, it must recognise the ‘intruder’ (aka the antigen, in scientific terms) as being foreign and dangerous. Then, it sends out soldiers to fight off the infection.

One of the ‘soldiers’ sent out by white blood cells is called Immunoglobulin E (IgE). IgE binds onto mast cells, causing them to release stored histamine. Histamine is the signal the ‘army’ is waiting for – it binds to cells, causing them to swell and leak and giving rise to the typical allergy symptoms: redness, swelling, itchiness, discharge, shortness of breath, etc.  The function of these symptoms is to ‘kill’ the ‘intruder’.

This is all very good when there is a threat of infection from a pathogen. But, an allergy is when the ‘army’ makes a mistake and over-reacts by sending out huge amounts of histamine even when the ‘intruder’ is harmless – a dust mite, an insect bite or a component of your horse’s dinner.  Itchiness, scratching, head-shaking, inflammation, breathing difficulty, etc is the result.

How do we fix it?

To fight an allergy, we need to somehow interrupt this chain of events.

Corticosteroids, very commonly prescribed for allergies, especially respiratory ones, works by decreasing inflammation at the genetic level.

Anti-histamines stop the histamine from attaching to the cell by blocking the receptors it binds onto and thereby stopping the allergic reaction.

Both corticosteroids and anti-histamines can have serious side effects, especially if used on a long term basis. Corticosteroids suppress the immune response, weaken bones, contribute to high blood pressure, diabetes and weight gain. Anti-histamines cause drowsiness (although the newer second generation drugs are better) and can contribute to liver damage and (in humans) Alzheimers.

Is there a natural way?

The very best way to treat an allergy is to identify the offending allergen and avoid it.  But often, this is like looking for a needle in a haystack. Expensive intradermal skin tests, where different allergens are injected and responses noted can be done. But even this is not guaranteed to track the offending substance down. The serum allergy test is cheaper and easier, but often inconclusive.

Let me tell you the herbs and nutrients I used on my horse last summer, which completely stopped the allergic reaction in three days.


A deficiency in Magnesium often results in a tendency towards developing allergic reactions. And, in respiratory allergies, Magnesium relaxes the muscles around the constricted airway.


Supervet, Dr Kellon, found Spirulina (Blue Green Algae) to be very effective in reducing the immune response in horses, especially in Sweet Itch.

Ascorbic acid

Vitamin C acts to decrease the production of histamine.


This South African tea contains a potent anti-oxidant called Aspalathin and in humans, has been found to have anti-allergic benefits.


Zinc helps to break down histamine.


Copper is an essential component of the super-anti-oxidant, enzyme, Superoxide Dismutase (SOD).


Otherwise known as the ‘botanical with a brain’, acts as an immune modulator – this means it decreases immune response in allergies and increases immune response in infections.


These are naturally occurring molecules in many plants. They act as mast cell stabilisers and stop the mast cells from releasing their load of histamine.

This mixture of herbs, vitamins, and minerals was able to get rid of Cas’s skin allergy in three days. Then I reduced the dose to about a quarter of the original dose and he was fine for the rest of his stay.

If you can’t pinpoint the exact cause of your horse’s allergy – whether it be a skin allergy or a respiratory allergy or some mixture of both, I strongly recommend using a natural remedy like one or all of the above, in small doses. It fixes the problem with zero side effects.

by Beryl Shuttleworth (BSc Hons Biochem, BSc Biochem/Zoology, Pr. Nat. Sci.) from The Herbal Horse

Precautions: This article is an advisory post only. Although herbal treatments are widely known for its safety if used correctly, there are a few factors to consider.  If you are giving any other type of drug or medication to your horse, please check with your vet to make sure it is still safe to administer herbal supplements. Any herbal supplements you administer is at your own risk.