Management and Therapy Guide for Horses with Allergies

This blog will focus on the different ways you can manage horses with suspected allergies and the various therapies available. Please click here for further information on the diagnosis of allergies in horses.

KEY WORDS:

Allergen – a substance which causes your horse’s immune system to over produce antibodies

Allergy – an overreaction by your horse’s immune system resulting in the over production of antibodies and ultimately the occurrence of symptoms

The ‘allergic threshold’ is a term used to describe the point at which you start to see the symptoms associated with allergy, for example itching. How quickly this threshold is reached will vary between horses. For some one single allergen, perhaps midges biting (a type of insect hypersensitivity) or grass pollen (an environmental hypersensitivity) may be enough to push that particular horse over its threshold. For another horse it may be the accumulative effect of multiple allergens that push them above the allergy threshold resulting in the symptoms you see.

For this reason, it is really important that as many allergens as possible are identified and addressed with the aim of bringing the horse as far under its threshold as possible. This helps to decrease symptoms and reduce the risk of flare ups. The horse labelled C demonstrates why only managing part of the problem would leave some horses still showing symptoms.

Allergen avoidance

Environmental allergy – there are lots of ways you can alter stable management techniques to reduce a horse’s exposure to environmental allergens. Below is a list of handy tips:

Mites

  • Wash rugs and other textiles at hot temperatures and dry in the sun when possible as mites struggle in hot dry conditions
  • Store rugs over winter (once thoroughly clean and dry) in air tight packaging
  • Empty dry feed out of its packaging and store in resealable plastic containers, discarding the dust at the bottom of the bags
  • Consider buying smaller bags of food to ensure batches are kept fresh
  • Wipe your horses muzzle with a damp cloth after eating to remove any dust and food residue

Grasses and weeds

  • Exercise your horse on well-cut paths and roads, trying to stay away from long, flowering grasses
  • Consider stabling horses when pollen count is high or if grass is being cut/crops harvested nearby
  • Keep your paddock weed free
  • A pollen nose net can be helpful

Trees

  • Avoid exercise routes which pass alongside or through wooded areas during peak pollen season
  • Turn out away from trees where possible, or fence off areas to avoid direct contact
  • Keep hedge lines and trees well cut to limit flowering
  • Keep stables well ventilated and treat damp walls with a mould inhibitor

Moulds

  • Avoid heavy vegetation, such as ivy, around or over stables
  • Keep the yard free from fallen leaves
  • Keep all rugs and other textiles in dry conditions
  • Source good quality forage, free from mould and dust
  • Keep tack dry and clean as some moulds are common on leather

Insects

  • Consider altering turn out schedules to avoid times when biting insects relevant to your horse are most active (different insects are active at different times of day)
  • Ensure fly repellents are true repellents (which stop the insects from approaching and biting) not just insecticides (which may kill after biting occurs). Remember that frequent reapplication may be needed if it rains or the horse sweats
  • Fine mesh screens and fly tape can improve the stable environment
  • Having fans in stable blocks can help as midges are weak fliers
  • Make sure that fly rugs fit well and are free from tears, mud and faecal contamination as this will attract flies or allow them access
  • Accessorise rugs with ear nets, face masks, belly bands or tail covers

 

Food allergy – To diagnose a food allergy something called a food trial is done. This is where the normal diet is changed to a bare minimum number of foods, which are not thought to be likely to be contributing to the problem, to see if the symptoms improve. A ‘gold standard’ food trial would involve stabling the horse on rubber matting (no shavings or straw as this exposes them to certain types of allergens) and feeding only forage from a single grass source with water. If hard feed must be given this should be limited to a minimal number of ingredients. All supplements, treats and flavoured medications should also be avoided if possible. The trial should be conducted until there is an improvement which may take 6-8 weeks to occur. If the symptoms do improve then one type of food that was originally fed should then be reintroduced every 7 days to see if it causes a recurrence of the symptoms, otherwise the improvement could just have been a coincidence. A relapse will confirm a diagnosis of food allergy. Once problem foods have been identified these can then be eliminated from the diet.

Topical therapy

Shampoos and sprays can be used to help maintain healthy skin and repair the skin barrier where needed.  Some biting insects will not bite through layers of oil, so using certain products may help by providing a barrier on the skin.

Immunomodulatory drugs

Prednisolone and dexamethasone are steroids which can be used to ‘dampen down’ the immune response to an allergen. There are known side-effects to steroid use in horses and they cannot be used under FEI rules, so you will need to discuss with your vet if they are appropriate for your horse. When given short-term at the recommended dose they are very effective in offering relief from allergic symptoms. Certain types of antihistamine tablets can also be used, but their effects are very variable, and they don’t always stop the itch.

Allergen Specific Immunotherapy (ASIT)

If the individual allergens have been identified, allergen specific immunotherapy treatment (ASIT) can be beneficial. Identification of allergens can be done either by a blood test (serological testing) or a series of injections into the skin (intradermal testing). For both methods the results should always be interpreted alongside the history and symptoms. The allergens thought to be contributing to the symptoms seen can then be made into a bespoke, individual treatment which is used to gradually desensitise the horse to the suspected problem allergens.

Allergy is a lifelong condition with no quick fix. Treatment often requires a multi-modal approach which may include environmental control, topical and systemic therapy, and allergen specific immunotherapy.

If you would like to find out more about equine allergy please click here.

Or direct any questions you may have to our customer services team on 0800 3047 047 or customer.services@avacta.com

Written by Emma Kilmurray – Customer Service Team Leader

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