Environmental allergies

Golden retriever dog panting and lying on grass with tennis ball and trees in background

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bleeding dog paws due to chewing from allergies

Russell Sprout chewed his paws raw in the summer due to environmental allergies.

Introduction

[00:03:08] So now that you have a better understanding of flea and food allergies, today’s episode is going to focus on environmental allergies. I’d like to politely ask you to take a look at that ugly mug you see on the podcast art.That scruffy face and snaggletooth, they belong to my dog, Russell sprout. Russell ran out in front of my car while I was driving to class during my first year of vet school. Don’t worry. I didn’t hit him. I pulled the car over, scooped him up and tried to figure out where he came from. And when no one claimed him, he became part of our family. He also became the inspiration behind my love of dermatology. Russell developed seasonal allergies. The first summer that I had him, it was really mild and we managed with lots of medicated baths and just a touch of steroids for a very short period of time. But by the time I got to my fourth year of veterinary school, his allergy season was longer and much more severe. Luckily it was at that time that I had my rotation at the Animal Dermatology Clinic in Pasadena. With the help of my lovely mentor, Dr. Charli Dong, we allergy tested Russell and I got him started on allergy specific immunotherapy, also known as allergy shots or allergy drops. I was completely fascinated, fell in love with the subject and with that clinic, and I wound up doing my residency there after graduation and internship.

Dog with chronic allergies
Dog with chronic allergies

Dogs with environmental allergies can often have redness, hair loss, itching, and infection on their neck and chest. Both dogs seen here have chronic environmental allergies.

Clinical Signs

[00:04:24] As a result, environmental allergies are one of my favorite things to discuss. As I mentioned in our episode on food allergies, the clinical signs of environmental allergies can look almost identical to food allergies. There are some things that we can use to raise or lower our suspicion of whether it’s food or environment, but it’s important to understand that the diagnosis of environmental allergies, which is also known as atopy, is a diagnosis of exclusion.  What that means is you’ve gone through the steps to rule out all other causes of itch, like infection or flea allergies or food allergies, and all you’re left with is environmental allergies. 

[00:05:03] Some of those little things that we can use to increase our suspicion of environmental allergies would be age. So, like I mentioned before, food allergies appear in much younger animals. Whereas environmental allergies usually begin between one to three years of age, but there’s some wiggle room on either side of that. Like I have mentioned previously, not all dogs read the textbook. It is unlikely to see older dogs develop environmental allergies if they haven’t previously had skin disease  unless they’ve moved to a different geographic region in the last year or two. Seasonality would be a big indicator that environment is more likely the cause of the allergy. So if the animal does totally fine throughout most of the year, but during certain months they are uncontrollably itchy, there’s probably something blooming during that time that’s causing an environmental allergy. One important thing to mention is that as an animal ages, they can start off by being really highly seasonal with their allergies progressed to longer allergy seasons, and then eventually develop year round allergies if the underlying allergy is not addressed. The last difference between environmental and food allergies is that environmental allergies don’t typically cause gastrointestinal issues but as I mentioned before, food allergic dogs may or may not have gastrointestinal issues.

Paw of dog with allergies

Dogs with environmental allergies will often lick their paws excessively. The first image shows slight brown staining from excessive licking. The second image shows the toes separated, revealing more redness and irritation than initially noticed.

Infected claw fold
Red, swollen paw

Paws can be severely affected in dogs with environmental allergies. Claw folds, as seen in the first image, can become inflamed, red, and infected, worsening the itch associated with allergies. The skin between the toes, as seen in the second image, can become severely swollen and uncomfortable to walk on. 

Diagnosis

[00:06:20] When it comes to diagnosis of an environmental allergy, if an animal clearly has a seasonal component to itch, I usually don’t wait to do a diet trial before I diagnose an environmental allergy. If the itch is non seasonal, so it’s present all year round, I’ll usually start with a diet trial and before we challenge feed to determine if there is a food allergy, I’ll see how itchy the animal is off all anti-itch medication and just the prescription diet alone. So if the itch comes back pretty quickly after stopping anti-itch medication, but before we’ve introduced any other food into the diet, I’m pretty confident that there’s an environmental component to the animal’s allergies.

[00:07:00] Once we’ve reached a diagnosis of an environmental allergy. I need to discuss what that means for the pet with the owner. For the overwhelming majority of pets, allergies are not something that we can cure, they’re something that we’re going to manage long-term. So I do my best to manage allergic animals with the safest, most effective medications.

Cats with environmental allergies scratch their bellies by overgrooming with their rough tongues, causing hair loss.

Cat with eosinophilic plaque on face
Cat with eosinophilic plaque on belly

Eosinophilic plaques from allergies on the face and ear of a cat in the first image. The second image is a cat with overgrooming and eosinophilic plaques from allergies on it belly.

Treatment: Symptomatic medications vs Desensitization

[00:07:18] When I think about medications used for environmental allergies, I like to put them into two big categories in my mind. The first category is symptomatic treatment. These are medications that are designed to treat itch and inflammation. Medications that I include in symptomatic treatment are Apoquel, Cytopoint, steroids, and Atopica. All of these medications will treat the symptoms of allergy, but if you stop giving the medication, the allergy is still there and the animal will start itching again. You’ll notice, I didn’t mention anti-histamines when I talked about the medications I include in symptomatic treatment and that’s because typically for dogs with environmental allergies, less than 10% of them will respond to an anti-histamine, so it’s not something that I think is effective enough to consider as my symptomatic treatment. Bathing is also a really important symptomatic treatment and almost all of my patients are prescribed a medicated shampoo to use on a regular basis. Bathing with cool water removes pollens from the surface of the skin, it repairs the skin barrier so pollens the animal comes in contact with are less able to get under the skin and cause an allergic reaction, and medicated shampoo is often anti-microbial, so that reduces the recurrence of skin infections that are common in pets with allergies. 

[00:08:31] The other category of treatment for environmental allergies is desensitization and this is my preferred treatment for environmental allergies long-term. What desensitization means is that we’re training the immune system to be less reactive to the things in the environment that it’s currently overreacting to. Desensitization minimizes the amount of symptomatic treatments that we just talked about needed long-term. To find out what the immune system is overreacting to we perform allergy testing, and this can be done with either intradermal skin testing or a blood allergy test, or both. 

Canine skin test

Intradermal skin testing on a dog (first image) and a cat (second image). Notice the large, red wheals (hives) in this dog with severe grass and tree allergies. Cats require a dye called fluorescein to be able to identify the reactions in their skin, which glow when viewed with a special lamp.

The results are used to formulate allergy specific immunotherapy (ASIT), also known as allergy shots, to help desensitize the animal’s immune system to what they are overreacting to in the environment, reducing the recurrence of itch and infection.

Allergy Testing: Blood (serum) vs Skin (intradermal)

[00:09:07] Intradermal skin testing involves giving the animal a mild twilight sedative so that it holds still, and it doesn’t feel the injections that we’re giving into its skin. Once the animal is sedated, a patch of hair shaved on the side of the body and a series of about 80 injections are given. What happens next is we watch for a reaction of the skin at the site of the injection to determine which allergens the animal is allergic to. That reaction is the release of histamine from mast cells that live within the skin. Skin testing does require animals to be off certain types of medications, such as steroids and anti-histamines, which can interfere with the skin reaction. In certain breeds, such as English Bulldogs, French Bulldogs, or any of those other smush face breeds, technically known as brachycephalics, this may require general anesthesia and that’s to protect their airway because these breeds tend to have difficulty breathing. The results of the skin tests are available immediately. The sedation is reversed and the animal goes home shortly after the procedure is finished. Intradermal skin testing should only be performed by somebody who has received special training in this procedure, like a veterinary dermatologist, so that they understand how to perform the test appropriately and interpret the results.

[00:10:19] Blood allergy testing involves pulling a blood sample and sending it to a very specific laboratory that evaluates circulating antibodies to different environmental allergens. For blood allergy testing, animals don’t have to be sedated and they don’t have to stop any medications. So this is a good alternative for some of those patients where you can’t get them off of steroids or sedation might be risky for them. Depending on the lab that is being used, results can take one to two weeks. If there’s not a veterinary dermatologist in your area, this can be performed by your family veterinarian and most of these labs that run blood allergy tests have a specialist who can help your family veterinarian interpret the results. Some dermatologists prefer to perform both skin testing, to look for that histamine release within the skin and blood testing, to look at the circulating antibodies, to give them as much information as possible when coming up with a recipe. 

Russell Sprout receives his allergy shot at home:

Allergy Specific Immunotherapy

[00:11:11] Whatever testing your veterinarian decides to go with the goal of the testing is not just to see what the animal is allergic to in the environment. In contrast to food allergies, where your goal is avoiding the thing that the is allergic to, there are very, very few allergens in the environment that the animal can effectively avoid. Things like dust mites, which are a very common allergen, are ubiquitous in the environment, and they’re impossible to avoid. The goal of the allergy testing is to use those results to guide your treatment based on what the specific animal is allergic to in the environment. 

[00:11:45] We come up with a recipe for allergy specific immunotherapy for that individual pet that desensitizes it to its specific allergens. Desensitization is through either allergy shots, which are given underneath the skin, usually by the shoulders, or allergy drops, which are administered using a small pump to give drops underneath the tongue. There are some dermatologists who are doing intralymphatic desensitization, so the animal gets an injection directly into their lymph node. That would be something that’s done under the guidance of a veterinary dermatologist and not done at home like the allergy shots or the allergy drops. Because the allergy shots are given by pet owners at home, there’s no need to come into the vet each time the pet needs an injection. You can visit the website for video of Russell Sprout getting his biweekly allergy shot at home. Russell is not a happy go lucky golden retriever, who will let you do anything that you want. He is as feisty as he is ugly. So if he can be trained to look forward to his allergy shots, I truly believe that most pets can successfully receive their shots at home. 

[00:12:51] Depending on which study that you look at about 60 to 75% of dogs who are being desensitized will have improvement of their clinical signs related to allergies and that means a reduction in both itch and the recurrence of infections, and that leads to a decrease in the need for those symptomatic medications over the course of their lifetime. About 10 to 15% of animals may have some type of seasonal flare in which they require a short course of anti-itch medication to help manage the flare and about 10 to 15% of animals may not respond to the allergy shots. For those pets, we work to find the safest, most effective symptomatic treatment to manage their allergies long-term. 

[00:13:29] Because desensitization is retraining the immune system, it takes some time to become effective. It’s important to expect that your animal will likely be on some type of other anti-itch medication for up to a year after starting the allergy shots. Some pets may respond to the shots within the first six months, which is great, but usually around 10 months or longer is more likely. There are a lot of different protocols for how often allergy shots are given, but the goal is to be able to reduce the frequency with which the animal is getting injections, once we’re past the induction stage, where we’re just starting out, and into the maintenance phase. Most animals who are maintained on allergy shots in our practice typically need injections once every two weeks, but every animal is different. So it’s important to have an ongoing relationship with a veterinarian who’s comfortable with long-term management of environmental allergies, such as a veterinary dermatologist. And for some patients, after a few years of allergy shots, we can even reduce the frequency further. 

[00:14:27] Allergy drops, which are a liquid given underneath the tongue are a little bit different than the shots they’re also given by the pet owner at home. However, instead of getting to a maintenance phase where they only need the shots every two weeks, the drops have to be given twice a day, every day in perpetuity. So kind of a drawback there as far as reducing the frequency that you’re needing to give treatment. 

Conclusion

[00:14:51] It’s important to understand that allergies are a chronic skin condition and unfortunately they require a lifelong management. Effective flea prevention is critical for any patient with allergic skin disease and about 80% of animals with environmental allergies are also allergic to flea saliva. It’s really tough to tell the difference between food allergies and environmental allergies, just based on the appearance of the animal alone, so working with your veterinarian to figure out what the primary cause is will go a long way towards minimizing your frustration.

[00:15:23] It is possible for animals to have both food and environmental allergies, making a prescription elimination diet trial under the supervision of a veterinarian important for that definitive diagnosis. Long-term management of food allergies is through avoidance of the protein to which the animal is allergic using a prescription diet.  Itch from allergies can be managed using symptomatic medications, such as a Atopica, Apoquel, Cytopoint, and steroids. The only treatment that actually retrains the immune system to not overreact to environmental allergens is allergy specific immunotherapy using either allergy shots or allergy drops formulated for the individual pet based on either skin testing or blood testing or both. 

[00:17:11] Today’s “Scratching the itch” is a website called Fear Free Pets. This website has a lot of great resources for minimizing stress in pets, and it’s geared towards pet owners, veterinarians and veterinary staff. I’ve included a link in the show notes to a specific article on their website regarding giving injections. The articles primarily geared towards veterinary technicians administering vaccines, but all the information is completely relevant for pet owners giving allergy shots at home to make it less stressful for the pet and the owner alike. You’ll very likely hear me talk about resources from Fear Free quite a lot on this podcast because creating a positive experience for my patients and my clients is a crucial part of how I practice. I would encourage you to look at today’s show notes on the Your Vet Wants You to Know website for a link to the Fear Free website and the specific article on giving injections. You can also find Fear Free certified veterinarians and veterinary practices in your area by searching the directory on their website.

References:

  1. Gedon, N.K.Y., Mueller, R.S. Atopic dermatitis in cats and dogs: a difficult disease for animals and owners. Clin Transl Allergy 8, 41 (2018).
  2. Noli, C, et al. Veterinary Allergy. John Wiley & Sons, Ltd, 2014.
  3. Nuttall, Timothy J., et al. “Update on Pathogenesis, Diagnosis, and Treatment of Atopic Dermatitis in Dogs.” JOUR AMER VET MED ASSOC, vol. 254, no. 11, pp. 1291–1300 (2019).
  4. Santoro, D. “Therapies in Canine Atopic Dermatitis: An Update.” Vet Clin North Amer: Small Animal Practice, vol. 49, no. 1, pp. 9–26 (2019).
  5. Saridomichelakis, M. N., Olivry, T. “An Update on the Treatment of Canine Atopic Dermatitis.” The Vet Jour, vol. 207, pp. 29–37 (2016).

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