Allergy Testing
Tuesdays with Tony
If you’ve been by the clinic lately, you may have noticed my fancy new hairdo. If you haven’t, I’ve provided a picture for you all to admire. A few weeks ago, my staff felt the need to show me off to all the lovely people at the University of Florida Veterinary School. Of course, I was happy to oblige to my adoring fans.
My staff explained to me that the reason for my visit was not just to get scratches and loves from the veterinarians, technicians, and students at UF, but it was important that I get checked out for allergies. The dermatology department at UF spent the day checking me out and performing intradermal skin allergy testing (IDAT) on me, hence my fancy new haircut. Did you know that horses can have allergies too? And did you know, my doctors here at Springhill Equine can perform allergy testing on your horse to help figure out why he/she likes to itch his/her mane off every spring, or why they tend to have trouble breathing during certain times of year?
What is Allergy Testing?
You may be asking yourself the question, what is allergy testing? Luckily for you, I have firsthand experience on this matter and can give you the lowdown on what exactly allergy testing is. There are two different types of test available. One is a blood test that measures certain protein antibody levels in the blood that may be causing your horse’s allergic symptoms. While sometimes this is a good starting point for allergy testing, intradermal testing is much more specific. Allergy blood testing can occasionally cause horses (and cats) to test positive to allergens that they are not actually allergic to. This is why my doctors choose to test your horse with the intradermal method. Using intradermal testing, my docs can test multiple different allergens that may be causing your horse’s discomfort. In order to provide you all with a play-by-play of what occurs during intradermal testing, I had this testing done during my visit at UF.
Why do we perform Allergy Testing?
The main reason we perform allergy testing is for the comfort of your horse. The goal of allergy testing is to identify specific allergens that your horse is reactive to so immunotherapy can be developed and your horse can be treated.
How do the docs perform intradermal testing?
The first step of intradermal allergy testing in to discontinue all allergy medications. I know that up until my appointment at UF, I spent way too many valuable napping hours scratching. I suppose it was the price to pay to figure out just what was causing all my discomfort. Horses also must be off all allergy medications. This means steroids, antihistamines, etc., for at least 14 days prior to testing. After your horse has been off his/her medication, the next step is to bring them into the clinic to see my docs. While you’re here you might even get a personal “cat” scan from yours truly. You’ll leave your horse with me for the day for monitoring, while my docs do the heavy lifting and perform the tests.
So, now you’re probably wondering what will happen while your horse is in my care. First, the staff here will clip a rectangular pattern on one side of your horse’s neck. I keep a watchful eye on this part. I wouldn’t dare let a horse leave my clinic without an awesome new hairdo like mine. Next the staff will make a 6 by 6 grid in the clipped area with a permanent marker. This grid serves as a guideline to where the allergens will be injected to your horse’s neck. Next, 36 different allergens are injected just under the skin using a very small needle. This was my least favorite part of my visit at UF, though thankfully it was followed by lots of scratches and treats.
A positive control (something we know your horse will react to) and a negative control (something we know your horse will not react to) are also injected under the skin, so my docs have something to compare the test allergens to. One hour after initial injection, the docs will compare the test allergens to the controls and mark those allergens which have any kind of reaction. Your horse will be looked at again three hours after initial injection and the reactions will be recorded. For the rest of the day, I will hang out with your horse and keep him/her company while he/she enjoys some tasty hay and my staff ensures no further reactions are going to occur.
What does all this mean?
So, you’re probably starting to think this whole allergy testing thing is sounding pretty cool, and you would be right. You’re also probably wondering what the next step is after my docs have identified the allergens behind your horse’s discomfort. Now that reactive allergens have been identified, the docs will work with laboratories to develop immunotherapy specific to your horse. I too, got my own special immunotherapy developed specifically to treat the allergens my body was reactive to. I guess that makes me a pretty special cat, but of course we already knew that.
The goal of the immunotherapy is to slowly expose your horse’s immune system to low doses of allergens and gradually increase the dose. This will desensitize the immune system to the allergen so when your horse is exposed to it, it no longer reacts. And that means no more itching, no more mane ruined by rubbing, no more tails rubbed raw, and no more trouble breathing. Fortunately, once your horse’s immune system has been desensitized to the most reactive allergens, immunotherapy will no longer be needed. A few shots for a few weeks/months seem well worth a life without scratching, if you ask me.
So next time you’re at the clinic, feel free to check on me and see how my immunotherapy is going. Actually, I’d be happy if you just give me pets and love. But, while you’re here, talk to my staff about setting up allergy testing for your itchy horse.
Until next week,
Tony
P.S. I listened to a particularly intriguing episode of Straight from the Horse Doctor’s Mouth this week. If you haven’t listened to it yet, make sure you put it on your list. It’s all about dentals, and I guarantee you will learn something you didn’t know!
Tuesdays with Tony is the official blog of Tony the Clinic Cat at Springhill Equine Veterinary Clinic in Newberry, Florida. If you liked this blog, please subscribe below, and share it with your friends on social media! For more information, please call us at (352) 472-1620, visit our website at SpringhillEquine.com, or follow us on Facebook!
Culicoides (kyōō′lĭ-koi′dēz′) is a species of gnat very common here in Florida. Many horses are actually allergic to the saliva of this gnat, so every bite by one of these annoying little devils sends the poor horse into an itching frenzy. The early signs of this gnat allergy include frequent scratching and hair loss in the ears, mane, base of tail, and chest. Over time the skin in these places will become thickened, there will be multiple open bite wounds, the hair will be completely gone, and the horse will constantly be scratching on anything and everything he can find. Horses with chronic Culicoides hypersensitivity will often develop a “cauliflower ear” appearance over a period of years. Once this happens, the ears will never return to their original shape.
Once the ear has gotten to a point where there is a secondary laceration, abscess, or hematoma, it can be difficult to treat. While we always try conservative options first, these horses sometimes have to undergo surgery under general anesthesia to drain the ear, followed by weeks with the ear taped down against the horse’s head to allow for continued drainage. No fun.
