Is it worth allergy testing my horse?
So the short answer is yes! But there’s a little more to it than that.
Since 2022 I’ve had three types of allergy test:
A blood test - with a sample sent to Avacta Animal Health for analysis
Intradermal skin testing and skin biopsy undertaken by the specialist dermatology team at Rossdales Veterinary Surgeons, Newmarket. This followed a referral by my local vet.
An alternative assessment by allergy specialist and retired amateur jockey, Tim Thomson Jones of the HTJ Centre.
Each has reinforced the other, and while intradermal skin testing is the gold standard, the Avacta Blood test was pretty accurate and served me well in the first year of recovery. I still look back on it to double check feed intolerances if I’m unsure as it’s so easy to read.
Since I undertook blood testing, Avacta has been bought out by Nextmune, who create allergy specific immunotherapy treatments for pets and horses. Following our visit to Newmarket we did start a programme of immunotherapy but sadly, C was too reactive to continue it. Even on very small doses, he was self-harming and the injection site was swelling. I felt it better to pause treatment and allow his immune system and general health to recover before exploring this any further. It is effective in 65-70% of cases so well worth exploring - it just wasn’t right for us.
What do blood test results show?
My blood test was undertaken in July 2021 and tested for a range of outdoor allergens (pollens) IgE, including:
Grasses: Meadow grass, Meadow fescue, Orchard grass, Perennial rye, Redtop, Sweet vernal, Timothy grass,
Weeds and Crops: Dandelion, Dock, Lamb's quarter, Mugwort, Nettle, Oil seed rape, Ox-eye daisy, Plantain, Ragweed, Red clover,
Trees: Alder, Ash, Beech, Birch, Hazelnut, Horse chestnut, Oak, Privet, Scots pine, Sycamore, Willow
Results are reported as a graded score between 0 (no reaction/negative) and 5 (very strong reaction). Allergens with test values higher than a score of 0, should be considered for allergen-specific immunotherapy (ASIT) and allergen avoidance providing the correct diagnostic work-up has been followed and relevant clinical signs are present.
Indoor allergens were also tested, and these included: Grain mill dust, Acarus siro, epidoglyphus destructor, Tyrophagus putrescentiae, Dermatophagoides farinae, Dermatophagoides pteronyssinus, Euroglyphus mayneii, Alternaria alternata, Aspergillus mix, Cladosporium herbarum, Penicillium mix.
Insects were also tested, including: Black fly, Horse fly, House fly, Mosquito, Stable fly and Culicoides.
Once again, results are reported as a graded score between 0 (no reaction / negative) and 5 (very strong reaction) with the exception of Culicoides where results are graded between 0 (no reaction / negative) and ++ (very strong reaction).
Results
C showed a positive reaction (score =1) for Dermatophagoides farinae - otherwise known as house dust mite and a ‘+’ for cullucoides (midges) - a strong reaction. Bear in mind only allergens that your horse has been exposed to will show up in the blood test, so there is room for change in the future!
Food Allergies
The Avacta test also looked at feed - including Barley, Corn (maize), Flaxseed, Oats , Rye, Soybean, Wheat, Alfalfa, Carrot, Pea and Sugar beet.
C showed reactiveness to barley, corn and oats (score =1) with all other foods tested, scoring 0. Lived experience does say something slightly different - as I notice an immediate itch response if I feed alfalfa, so always avoid it!
Intradermal Skin Testing
Image shows veterinary nurses at Rossdales, Newmarket putting cream on C after intradermal testing and a bath! With huge thanks to Rossdales for sending me this photo of our much loved patient.
When almost exactly a year to the day later, C began to show symptoms including severe itching, a breakdown of his skin and some alopecia, we decided to refer him to Rossdales for intradermal skin testing to really get to the bottom of it. The team there are absolutely amazing.
Typically horse are not given steroids after the intradermal test, but in C’s case his itching was so severe they did prescribe steroids. From the photo you can see he was very grateful for the bath, soothing cream and attention!
Diagnosis and Treatment
Rossdales diagnosed atopic dermatitis, sensitivity to all indoor dust mites and biting insects and a mild secondary bacterial infection.
Our treatment included:
Prednisolone: 1mg/kg dose once daily until the itch is well controlled.
Cetirizine: Anti-histamines are rarely enough on their own to control pruritis but can often help reduce the dose of steroids.
Topical treatments - including washing 2-3 times weekly with medicated shampoo, and later, a soothing shampoo. Shampoo helps remove allergens from the surface of the skin.
Supplements: Omega- 3 supplementation can help some horses. Cavalesse can also be useful in some cases.
Allergen avoidance: Full pasture turnout was the recommended management strategy but as and when C needs to be stabled, we should focus on trying to reduce exposure to stable dust, regular vacuuming and pressure washing of stables, removal of all bedding and use of rubber matting. Rugs should be washed regularly on a high temperature and can be frozen for 48 hours to kill dust mites.
Insect avoidance: Essential and achieved through use of appropriate sweet itch rugs and repellants.
Alternative tests and treatments
Tim Thomson Jones testing C for intolerances and allergies.
As C was still struggling, and with nothing left to test, in October 2022 we tried an alternative approach. With the support of my vets we contacted Tim Thomson Jones of the Horse Allergy Centre. Tim’s approach is more akin to chinese medicine than traditional forms of testing.
I was advised by a friend who had worked with Tim successfully, to ‘just go with it!’
Tim painstakingly tested C for deficiencies in vitamins and minerals, and allergens, looking closely at substances triggering a response in order to identify the severity of the allergy.
Once again, only substances that the horse has been exposed to in the same year, tend to show up in testing.
From this process we identified the following:
Very low levels in Magnesium, Zinc and Boron; extremely low in Iron
Positive intolerance to Mites, Harvest Mites, Storage Mites and the Culicoides Midge.
In our first year of testing, we discovered a positive intolerance to Formalin.
Having checked with the vet, we were able to confirm that Formalin (often used as a carrier in vaccines) was not used in our annual flu/flu + tet vaccine, so we weren’t sure where this came from.
Treatment
Tim’s treatment aligns with Traditional Chinese Veterinary Medicine (TCVM) - meaning a solution is prepared specifically for the patient and adminstered as drops, administered twice daily until Autumn/Winter when symptoms subside.
In May 2023 we repeated the test and found very similar deficiencies with the exception of the Formalin, which no longer appeared. This year, I had actually decided not to proceed with the sweet itch vaccine (too costly, no real evidence of improvement for us) so we concluded Formalin was probably used as a carrier in the vaccine. That would explain it being in his system in 2022 but not in 2023.
[Side note: this vaccine was originally used in cows for ringworm but is effective in many cases in reducing symptoms of sweet itch. It is administered by UK vets ahead of the midge season, used off licence and imported into the UK.]
Final thoughts
From my perspective, every test adds an additional layer of information that builds on what came before. It’s like peeling back the layers of an onion and knowledge is power!
So while I may decide not to continue with a prescribed treatment year-on-year, at the very least I understand the triggers and do my best to mitigate problems occuring through management of what my horse eats and his environment. While no year has been 100% perfect, I’m managing much better than I was before, C is happier than he was before, and when we have a ‘blip’, I immediately know what to do.
