Allergies in Dogs and Cats

As the yellow winds blow, we are seeing our annual spring uptick in pets who are suffering from seasonal allergies. So I thought it would be a good time to discuss allergy diagnostics and treatment.

The symptoms of allergies can vary. Most pets have some degree of itchiness, which leads to them scratching/licking/chewing, and then to hair loss. Sometimes unrelenting trauma to the skin causes an infection with bacteria, yeast, or both. Hotspots are also common. Allergies can cause chronic/recurrent ear infections as well. And pets with food allergies may have GI symptoms such as vomiting, diarrhea or soft stool, gastric reflux. Sometimes cats will show GI discomfort by pulling their fur on their abdomen. Any of these signs can have other causes as well, so diagnostics are very important. For example, GI signs can be caused by pancreatitis, inflammatory bowel disease, exocrine pancreatic insufficiency (EPI), protein-losing enteropathy (PLE), or even lymphoma (a type of cancer).

There are 3 major categories of allergies in pets:

1) External parasites, with fleas being by and large the most common cause of allergies. Other external parasites that cause allergic reactions are mites (scabies, demodex, walking dandruff), mosquitoes, and flies.

2) Environmental allergies. Pets can become allergic to pollens, molds, grasses, chemicals (cleaners, fragrances, etc.), materials such as wool or cotton, dust mites, pretty much anything.

3) Food. The most commonly reported food allergies in dogs and cats are chicken, beef, dairy, and egg (and fish for cats).

Unfortunately many pets have allergies in more than one category. For example, they can be allergic to fleas and to pine pollen. In many cases, treatment is multi-modal (flea control plus cytopoint for example) and in ALL cases, it's trial and error. With the exception of rare cases of environmental allergies being cured with immunotherapy after many years, allergies are not cured, only managed.

External parasites are the easiest allergy to diagnose and to treat, especially fleas. However we still see pets suffering from flea allergies because of pervasive myths regarding fleas.

Top left: flea dirt (poop) on a dog

Top right: flea

Bottom left: demodex mange mite under microscope from a skin scraping

Bottom right: scabies mange mite under microscope from a skin scraping

Flea Myth #1 If your pet has fleas, you'll be getting bit by fleas too.

Reality: fleas really like the higher body temperature of pets and will only bite people if they are desperate.

Flea Myth #2 You don't have to treat your pets during the winter.

Reality: What winter?! This area does not sustain temperatures low enough to kill fleas. It takes 5 straight days and nights of freezing temperatures to kill fleas. You tell me the last time this area has experienced such horror. I did not move to the South to be exposed to extreme cold on a regular basis! If I'm comfortable, so are fleas.

Flea Myth #3 Bathing with Dawn kills fleas.

Reality: Yes, it does. But that doesn't prevent more fleas from getting on your pet almost instantly. You need to use products that protect your pet between baths.

Flea Myth #4 Feeding your pet garlic or brewer's yeast or other things prevent fleas.

Reality: That's just a straight-up lie. Plus feeding garlic can kill your dog or cat.

So what's a pet owner to do? Luckily there are many OTC and prescription products available to help control fleas and ticks, many of which also prevent mites. Over the counter options are limited to topical products such as shampoos, dips, sprays, spot-ons, and collars. Prescription products can be combined with heartworm prevention and GI parasite control, such as Advantage Multi, Revolution, or Simparica Trio, and come in both topical and oral forms. For pets who are bathed frequently or go swimming a lot, oral products tend to work better and longer.

Example of Flea Control Products

We know there was a USA Today story about Seresto flea collars killing pets. There were a lot of issues with story, and it was very poorly researched and reported. First of all, none of the cases were confirmed to have been caused by Seresto collars. Just because you put a collar on your pet and it dies later doesn't mean the collar killed the pet. Correlation is not causation. Secondly, the ingredients in Seresto, flumethrin and imadicloprid, are very poorly absorbed through the skin. For those ingredients to be both absorbed through the skin and enter the blood stream to cause the symptoms reported would be pretty much impossible. We do see topical/skin related problems sometimes with Seresto collars and this makes sense. But seizures do not make sense. Third, we strongly suspect that most of the problems are not real Seresto collars, but cheap knockoffs. We have been seeing grey flea/tick collars that are definitely NOT Seresto collars but were purchased as such from Amazon or eBay. I used Seresto collars on my dogs for *years* and I know what they feel, smell, and look like. The only reason I switched is that my dogs are going swimming now, and it was easier to give them Simparica Trio once a month for all their parasite control needs. If you buy a Seresto collar, get it from a legitimate source such as PetMeds or Chewy, who buy them directly from Elanco. You can read more about the Seresto story here.

Tangent aside, flea allergies are an easy diagnosis and treatment, even with secondary skin infections. We can fix those very quickly. Sometimes getting a flea infestation under control is difficult. You have to treat every pet in the home, and do environmental control also. Else you'll have fleas hatching for the next 3 months and who wants that?!

Other external parasites can be a little more tricky to diagnose, especially scabies mites, because they just don't like to show themselves on a skin scrape. We usually cover our bases by prescribing a flea/tick medication that also kills scabies if scabies are suspected.

Your vet can help you decide which product(s) are best for your pets based on their health concerns, risks for exposure to specific parasites, your personal preference as far as topical vs collar vs oral, and cost.

Next on the list are environmental allergies. The only way to test for environmental allergies is with allergy testing. Luckily, serum (blood) allergy testing has dramatically improved over the years, so that intradermal (skin prick) tests are not needed.

There are 2 basic ways to treat environmental allergies. In pets who experience just seasonal issues, we can treat symptomatically using a variety of prescription medications, such as steroids, Cytopoint (dogs only), or Apoquel. These medications control the itching and scratching, though only steroids help pets with allergy-caused ear infections. Unfortunately steroids can not be used long-term due to very adverse side effects such as muscle wasting including the heart muscle, increased susceptibility to infection, weakening of ligaments and tendons which can cause torn ACLs and other serious injuries, etc.

The other option is immunotherapy, where we use the results from the allergy testing to create an individualized treatment consisting of just a little bit of what your pet is allergic to (desensitization). Over time, immunotherapy decreases the need for symptomatic treatment and in some cases even cures the allergies!

Last are food allergies. Unfortunately this category is so full of misinformation and bias that it's going to take a while to go through all of them, so I'll touch on the most important.

You probably noticed above that the most common food allergies are NOT TO GRAINS. This myth was started by Blue Buffalo which spent a lot of money to lie to the public in claiming that switching to their food would solve food allergy problems. In fact, switching to a grain free diet may kill your dog! Dilated cardiomyopathy has been linked to grain free diets in dogs (cats can safely eat grain free). More on that can be found here on the FDA website concerning the on-going research into this devastating problem.

Another myth is that feeding raw food can solve food allergies. This is also patently untrue. If your pet is allergic to chicken, it doesn't matter if the chicken is cooked or not. Plus most people do not know how to formulate a complete and balanced diet for pets. It's not easy, I've done it! The vast majority of recipes for home cooked or raw pet diets you see online are dangerously unbalanced in many nutrients, most notably calcium, vitamin D, and phosphorus, which can cause rickets, seizures, and death. If you want to make your pet's food, go to the BalanceIt website and follow the recipe exactly.

Yet another myth is that rotating your pet's food will help prevent allergies. There is no evidence this is true. Allergies are most likely a combination of genetics and the environment. However I'm not against giving your pet a variety of different proteins and carbohydrates. I'd leave out some proteins and carbohydrates from the rotation just in case your pet develops a food allergy later in life.

A lot of people switch their pet's food from one brand to another and get frustrated that their food allergy trial didn't work. More often than not, the new food has many of the same ingredients as the old food. Your pet is not allergic to the BRAND of food, they're allergic to one or more of the INGREDIENTS in the food. Switching from the chicken-based Dog Chow to Diamond Naturals Chicken and rice formula isn't going to work! In fact, you'd have to avoid corn, chicken, beef, rice, soybean, egg, and wheat to see if your dog is allergic to something in the chicken Dog Chow because the ingredients are much more extensive than just chicken and rice!


Some people believe that their pet can't be allergic to their food because they have been giving their pet the same food for a long time. The truth is that allergies develop over time, with each exposure to the allergen making the reaction worse. So your pet can only be allergic to foods that they've been exposed to many times. This makes sense if you think about people with peanut allergies. They couldn't have died the first time they were exposed to peanuts, else nobody with peanut allergies would be alive! It's that the reaction gets worse and worse with each exposure, such that with multiple exposures, just some peanut dust in the air can kill them.

There is only one way to accurately diagnose food allergies in pets, and that's by doing a complete diet trial. Blood, skin, saliva, and fur tests are sold, sometimes even by reputable companies, but the results do not correlate with reality. In other words, the tests can show your pet is allergic to a particular food that it is not actually allergic to, and the test can show your pet is NOT allergic to a food they ARE actually allergic to. In one fabulous experiment, researchers sent "fur" from a stuffed animal and water instead of saliva and the lab diagnosed allergies! OMG.

So, how you do a complete food allergy diet trial? I personally like to start with a hydrolyzed diet, such as Purina HA or Hills Z/D. Other vets might do a novel protein and carbohydrate food trial. Neither approach is wrong. It's hard for pet owners to accurately remember every single protein and carbohydrate their pet has ever been exposed to so that you can actually find a novel protein and carbohydrate source. While some pets will still react to a hydrolyzed diet, the chances are very low.

The pet can eat NOTHING BUT THIS SPECIAL DIET for 8 weeks. That means nothing but that one special food and water shall pass your pet's lips- no treats, bones, dental chews, rawhides, anything. If the symptoms clear up, then you have to "challenge" the pet by feeding the old diet. If the symptoms come back when the old diet is fed, then you know your pet is allergic to something in their food. It doesn't tell you what they're allergic to, just "something" and probably not the grain. What we do at this point is put the pet back on the hydrolyzed diet, then start testing one ingredient at a time to see if there is a reaction. One week, we might add cooked chicken to the hydrolyzed diet. If there is no reaction with chicken, we might try rice, and so on. If your pet doesn't react to chicken or rice, then you can probably find a commercial food that contains just chicken and rice with vitamins and minerals and feed that instead of the expensive prescription diet.

I do know some people are so happy that their pet's allergy symptoms clear up on the hydrolyzed diet that they don't do the challenge part of the trial. The challenge is important, because it proves the pet has a food allergy and it wasn't just coincidence that the symptoms cleared up. It's that old correlation is not causation thing again! Maybe your pet is allergic to pine pollen for example, and 2 months later the symptoms are cleared up because the air is no longer yellow with the stuff, not because the food allergy trial worked.

Hopefully this post was helpful in clearing the air about pet allergies:)

If your pet is exhibiting symptoms of allergies, we can help! We have a ton of experience in dealing with all kinds of allergy problems and can help you develop a reasonable diagnostic and treatment plan. Call or text us at 800-993-7921, email us at, or go to our online appointment scheduler.

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