Allergic disease in horses is a lifelong condition which can change over time. A multimodal therapeutic approach is the best way to achieve long-term management after first identifying all underlying primary triggers.
Please note: The pet owner section of this website is for reference only. We are unable, due to both contractual and data protection law, to give clinical guidance or discuss test results directly with anyone other than the submitting veterinary practice. Irrespective of this, we would always advise contacting your own veterinary practice anyway as they are best placed to explain these results/discuss your pet’s case in the correct context factoring in all other test results, clinical findings and your pets previous history to ensure the test is not interpreted in isolation.
What is an allergy?
A reaction to a common substance such as a grass or flowering plant, mould, dust mite or insect. The things which trigger the allergy are known as allergens. Allergens enter the body by being breathed in, eaten or absorbed through the skin and cause the horse’s immune system to overreact which results in the symptoms you see.
How common is equine allergy?
Approximately 10-20% of horses will suffer from allergies at some point during their life. Allergies can affect any breed, age or sex of horse, however insect bite allergies (including sweet itch) are particularly common in Icelandic and other native ponies and cobs.
Most horses will start to show skin and gut allergic signs between 2 to 5 years of age, whereas breathing signs tend to be at around 7 years or older.
Changes such as moving to a new pasture with more midges, bringing in for stabling from living outdoors, or a seasonally higher pollen count can also trigger symptoms starting.
SYMPTOMS OF ALLERGIES AND COMMON CAUSES
SKIN SIGNS OF ALLERGY
- Itching – can lead to hair loss from rubbing and scaly skin
- Hives (fluid filled bumps) – with or without pruritis
- Skin lesions (spots or raised bumps)
Sweet itch (insect bite hypersensitivity) – This is usually associated with midge saliva although it can be caused by other biting insects and tends to be seasonal being worst in spring/summer. Symptoms generally involve frequent rubbing, mainly around the mane and tail region. Sometimes due to the trauma caused by rubbing, secondary infections occur.
Other allergies causing skin signs – atopic dermatitis, contact allergy or food allergy
RESPIRATORY SIGNS OF ALLERGIES
- Frequent coughing
- Increased effort to breath at rest
- Reduced ability to exercise
Equine asthma – This condition was previously known as recurrent airway obstruction (RAO) or chronic obstructive pulmonary disease (COPD) with summer pasture associated versions. Equine asthma is associated with the airways of the horse being inflamed and narrower than normal (causing any noise you may hear) along with increased mucus production. Asthma can be caused by airborne allergens such as mould or fungal spores, dust mites and pollens, both outdoors and in the stable. Equine asthma is usually treated through a combination of allergen avoidance/reduction and medication to reduce the inflammation and help open up the airways. Many other things can contribute to, or cause, respiratory symptoms in horses and these may need to be investigated first.
GASTROINTESTINAL SIGNS OF ALLERGIES
- Chronic colic
- Long-term weight loss
Food allergy – in horses is much less understood about food allergy than in either humans or dogs. Skin symptoms can also be associated with it.
To diagnose food allergies in the horse, a dietary trial must be performed which typically will last at least 4-6 weeks. The SENSITEST food test can be helpful in selecting appropriate foods to be used for this trial. Your veterinary surgeon will look at the foods which are negative to both IgE and IgG on this test, and combine this information with your horse’s dietary history to help plan a dietary trial. If your horse improves on the dietary trial, ideally, they should then be given the original diet to eat again and the response monitored. This is to confirm the improvement seen in symptoms was due to the change in diet and not something else. These foods can then be permanently removed from the diet.
DIAGNOSING ALLERGY IN HORSES
STEP 1 – Rule out mites and lice and also bacteria, yeast or fungal infections
STEP 2 – Consider a dietary trial to rule out food allergies. An allergy blood test can help select the foods to use in this trial.
By ruling out all of the other causes, you now have the diagnosis of an allergy!
STEP 3 –The final step is to work out what allergens may be causing it, this can be done by either:
- Blood allergy testing – a blood sample is taken by the vet and sent to the laboratory, where it analysed and the results are returned to the practice. The results are then interpreted by your vet, taking into account your horse’s history and symptoms
- Intradermal skin testing – small amount of the allergens are injected into the skin while the animal is sedated and the amount of reaction is measured, this procedure is carried out by a specialist veterinary dermatologist
As part of this work-up, they may suggest sending off a small sample of blood to us to carry out a SENSITEST® allergy test.
Following this, we will provide you and your vet with your horse’s results and a personalised results pack. If allergy is identified as a contributing factor, your vet will provide you with suggestions for managing your horse’s condition.
If you’re concerned, please speak to your vet.
Which allergens do the Sensitest panels test for?
- Sugar Beet
- Corn (Maize)
- Cod Liver Oil
Environmental Indoor Allergens
- Acarus Siro
- Euroglyphus maynei
- Lepidoglyphus destructor
- Tyrophagus putresentiae
House Dust Mites
- Dermatophagoides farinae
- Dermatophagoides pteronyssinus
- Alternaria Alternata
- Aspergillus Mix (Amsteldami, Flavus, Fumigatus, Nidulans, Niger)
- Penicillum Mix (Camembertii, Chrysogenum, Digitatum, Notatum, Roquefortii)
- Cladosporium Herbarum
- Grain Mill Dust
- Black Fly
- Horse Fly
- Stable Fly
- House Fly
Environmental Outdoor Allergens
- Meadow Grass (Kentucky bluegrass)
- Cocksfoot/Orchard Grass
- Meadow Fescue
- Red Top, Bent Grass
- Rye, Perennial
- Sweet Vernal
- Daisy (Ox eye)
- Dock, yellow/Curly
- Lamb’s Quarters (Fat hen)
- Red Clover
- Oil Seed Rape
- Ash (white)
- Birch (white)
- Horse Chestnut
- Oak (Red, Common)
- Scots Pine
WHAT DO YOUR RESULTS MEAN?
The SENSITEST® allergy test identifies levels of antibodies in the animal’s blood which may correspond to the clinical signs of allergy. These results pinpoint the potential offending allergens and the level of reaction – a Class Score on a scale of 0-5 or +/++ for Cullicoides. Any score of 1 and above should be considered significant. In conjunction with the work already carried out by your vet these results can be used to identify ways of managing the condition.
Results from the SENSITEST® food allergy test can be used to tailor a food elimination dietary trial for your animal. Your vet will be able to advise suitable commercially prepared foods or a home-prepared diet that you may wish to try. Food tips & advice are included in your results pack to assist in monitoring your horse’s diet.
Where possible you should try to avoid or reduce exposure to allergens. For hints and tips on how to avoid different indoor and outdoor environmental allergens, please follow the links below.
Can be useful for short-term effective relief of itching, especially when managing flare-ups. They are not suitable for all horses and can have serious side-effects, particularly when used over a long time period. They are also on the FEI prohibited substances list (so you may not be able to compete while your horse is being medicated with them).
If the allergens suspected of causing the allergy have been identified, allergen specific immunotherapy treatment (ASIT) can be beneficial. The therapy is an injection made up of these specific allergens and is therefore individual to each horse. Gradually increasing doses of the injection are given which desensitises the horse to the suspected problem allergens over time.
Our Immunotherapy leaflet can be downloaded here
Antihistamines and essential fatty acids
Additional therapies which may help in some horses.
Important for control of insect allergens.
The act of bathing the horse in cool water is itself beneficial as it:
- rehydrates the skin
- causes the blood vessels in the skin to shrink which reduces inflammation
- Mechanically washes off both allergens and any bacteria or yeast
Numerous different veterinary shampoos are available which may also help, your vet will be able to advise on the best one for your horse.