Common Dog Allergies and How They're Treated

Posted by Chris Vanderhoof, DVM, MPH on Apr 20, 2020 8:00:00 AM

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It’s that time of year again, when the dead of winter has passed. As spring arrives, we’re seeing leaves on the trees and flowers blooming.



Unfortunately, we also tend to see many allergies bloom in dogs as well at this time of year. And some of these only worsen as spring moves into summer.

 

Allergies in dogs can be very frustrating, from nasal congestion and sneezing to watery, runny eyes, to chronic recurrent skin itchiness and irritation. Even acute allergic reactions to bites, stings, or medications are concerns for our pups.

 

In this article, we’re going to discuss some of the most common types of allergies dogs face and some ways we have of addressing them.

What Are Allergies?

It may seem like a silly question because in one way or another, most of us suffer from allergies and they’re a part of life. But it’s a question worth asking, both to understand why they happen, but also to understand the ways we have to address them.

 

An allergen can essentially be any substance that the body’s immune system recognizes as “foreign,” requiring that it be targeted.

 

Most substances that are allergens are harmless. What makes one of these harmless substances allergens depends very much on the individual nature of a dog’s immune system.

 

For example, one dog may have a hypersensitivity to mold spores. There are literally hundreds of mold spores that float around in the air from fungal growths in the soil, landing on the skin, hair coat, or being inhaled or swallowed.

 

But where one dog may have absolutely no problem with mold spores, another one may develop a significant reaction to one or more. So for the first dog, mold spores aren’t really an allergen, they’re just mold spores.

 

But for the other poor dog, they are an allergen because his body has recognized them as such.

 

Allergies are extremely complex. An allergic response may occur after exposure to a substance just one time, or it may take several exposures.

 

Genetics can also have a part to play, with certain genes being turned on at certain times. A friend of my wife’s developed a sudden allergy to shellfish in her thirties. Her friend’s mom had the same thing happen to her too, supporting a family genetic history.

 

But regardless of these details of why allergies occur, there are some basics to understanding what happens when allergies occur.

 

When the body is exposed to a substance, the immune system, always on guard against invaders, will send out cells to identify the substance. In some cases, it may simply identify the substance and store that information for later.

 

When it does this, an antibody is formed. Antibodies come into play later, if there is a recurrent exposure to the substance. If the substance is seen again and seen as a threat, the specific antibodies will flock to it, releasing chemicals to start a whole cascade of inflammatory responses designed to target and destroy the substance.

 

But sometimes, even if the immune system sees something for only the first time, it will see the substance as an immediate threat. Cells that are more generalized, like mast cells, will still flock to the substance, releasing chemicals like histamine, leading to a similar cascade of a more acute inflammatory response.

 

These are the differences between an acute hypersensitivity reaction and a delayed hypersensitivity reaction. Unfortunately, predicting how or when these changes will happen is almost impossible because it’s entirely up to the individual’s immune system to decide.

 

It’s also impossible to fully understand why one individual’s immune system will react mildly to an allergen while in another, a severe reaction results. Consider a human’s allergy to cat dander. Some folks get watery eyes and a stuffy nose. But others, like one of my aunts, will develop severe, acute respiratory distress. Why the difference? Ask the immune system.

 

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Environmental Allergies

We’re going to start with the less life-threatening types of allergies because they’re more common, though they may actually be more frustrating than your acute allergic reactions.

 

With acute allergic reactions, which we’ll discuss a little later, it’s easier to avoid the allergens involved, or plan ahead, like in the case of a vaccine reaction.

 

But your chronic recurrent allergies are tough because there can be multiple offenders and they can be hard to pinpoint.

 

Environmental allergies are one such type and probably by far the most common type that affects our canine friends.

 

Unlike food allergies which we’ll discuss next, where we can at least work to eliminate consumption of the offending protein allergen, most allergens in the environment simply can’t be removed.

 

What are some of the most common types of environmental allergens?

 

According to an allergy panel conducted in 2016 by Douglas DeBoer, a veterinary dermatologist with University of Wisconsin, Madison, the most common environmental allergen might surprise many, because it’s not even outdoors.

 

It’s the dust mite.

 

There are actually a couple species of dust mites, but all are microscopic, and could be considered present in even the cleanest house. They don’t actually cause allergic responses by biting, but their skin and fecal matter can cause a significant allergenic response in people and pets.

 

I myself have seen them show up as strong positives on most pet allergy panels I’ve seen and are probably a significant irritating component of pets with year-round allergies.

 

The next most common? It’s hardly surprising, but pollens are the next biggest offender. There are just as many different types of pollen as there are grasses, flowers, trees, and other plants. So unfortunately, they’re pretty impossible to avoid. But fortunately, if your pup has an allergy to only a couple, you may see only a seasonal allergy issue that is not present most of the year.

 

Molds are next. Mold is commonly thought of as this singular thing that grows in between shower wall tiles or under the sink. But actually, there are many different types of fungal molds that exist outdoors.

 

Fungal molds are a big part of the cycle involving breakdown of organic matter like dead leaves and plants as fall sets in and plantlife prepares for the winter. They really like temperate, damp weather, not too cold, not too hot.

 

So, we tend to suspect mold allergies during the fall, during mild winters, and in late spring. Some regions that are always damp and humid may have issues with these allergens year-round.

 

Our last most common environmental allergen is not very well understood according to the 2016 panel, but insects (dust mites are technically arachnids like spiders and are not insects) may have a part to play. In city environments, cockroaches have demonstrated to cause allergy response in pets.

 

Environmental allergens are tough to avoid. But if we can’t avoid them, how do we deal with them? There are only two ways. One is to generally modulate the immune system using certain medical therapies available through your veterinarian.

 

The other is with allergy testing and developing allergen-specific immunotherapy from those results. Unlike people, who predominantly inhale allergens, the skin is the main allergy organ in pets. Thus, skin testing with a veterinary dermatologist is probably the most accurate way to do this.

 

That’s not to say that inhalation allergies don’t happen, because they do, but this is far more common in cats than in dogs. Research in dogs has shown that environmental allergens can actually penetrate the skin.

 

Allergen-specific immunotherapy is designed to desensitize the dog’s immune system to the specific allergens to which he or she is most sensitive. Some testing and therapy options may be available with your primary care vet, or referral to a veterinary dermatologist can be discussed.

 

For mild cases, some remedies like fish oil can be beneficial. Look for a product intended for pets that combines the essential omega-3 fatty acids DHA and EPA with other beneficial ingredients, like Aller-911 Allergy Aid.

 

There was one last major point mentioned in the 2016 allergy panel with Dr. DeBoer, and that was regarding contact allergies. In humans, contact allergies to products like jewelry, chemicals, perfumes, soaps, latex, and the like are very common. But in dogs this isn’t the case and is very rare.

 

Also rare are allergies to materials like carpet, rugs, fabrics, and furniture. Dogs predominantly have allergic responses to things that “blow around in the air” and foodstuffs.

 

So while using hypoallergenic detergent is a nice thought, it may be doing less to help your itchy pup than you might think.

 

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Food Allergies

Food allergies are less common than environmental allergies, but no less frustrating. In addition to those indoor allergens like dust mites, food allergies may be more likely in pups that show signs of skin itching, irritation, and recurrent skin infections year-round.

 

 

The digestive tract of dogs has a great deal of immune function. If you think about it, it makes a lot of sense. The digestive tract is the only inside part of the body besides the respiratory tract to be constantly exposed to foreign things.

 

Most food allergies occur to proteins and of these, meat proteins are most often implicated. Chicken protein and beef protein are the most common offenders, probably because they are such common sources of protein in diets.

 

This is why a pet having a non-specific “grain allergy” isn’t really a thing. It may come as a surprise to many pet parents. However, the idea of a “grain allergy” is more a product of clever marketing for grain-free diets than anything else.

 

Now, it is true that wheat gluten is a protein and a pet can have a wheat gluten allergy, just like a person with celiac’s disease. But in pets this is thought to be pretty uncommon, and wheat gluten itself is found in only a couple of grains, not all of them.

 

Having a digestive intolerance is certainly a thing however, and this can be where confusion develops. Some pets have more difficulty digesting some nutrients than others and simply require a more highly digestible diet, but this is not the same thing as a true allergy.

 

Food allergies can be frustrating to diagnose and treat, because the only reliable way to do either is to eliminate the offending protein. And if you don’t know what that protein is, how do you eliminate it?

 

One such method is with a hypoallergenic diet available through a prescription from your veterinarian. There are several out there that can work in different ways, but in each case, the goal is the same. By eliminating as many protein variables as possible, we’re more likely to see improvement.

 

Novel protein diets use a single, far less common protein, like rabbit or kangaroo. The idea here is that, as mentioned, dietary allergies are thought to develop over time to more common proteins. By using a less common protein, the body may not recognize it as a problem.

 

Hydrolyzed protein diets don’t have any whole protein components. The proteins in the diet are broken down into components so small that the immune system in theory should not be able to recognize them as foreign.

 

Using these diets is usually the best place to start, because they are formulated to not have any other protein “contamination” in them. Many over-the-counter diets developed for sensitive skin don’t need to abide by strict formulation guidelines.

 

So while salmon may be the main ingredient in a limited ingredient diet, there may also be a chicken protein byproduct included in a smaller amount to balance the diet. Sometimes these over the counter diets can work well, but there’s a great deal of variability in how they’re formulated.

 

But let’s say we’ve locked down a diet to try. A diet trial must then be performed for a minimum of 6-8 weeks. The diet must be fed exclusively, with no accidental ingestions of human foods, or treats, for the whole period.

 

Next to choosing the right diet to use, the trial itself can also be difficult because of how strict it needs to be. Let’s say you’ve been doing great with your pup on a strict diet trial for 3 weeks. Then, he gets into some chicken that was left out on the table. It was just an accident, but now you’ve got to start all over again from day one.

 

This is why many veterinarians will focus more on symptomatic therapy for environmental allergens when a pup starts to show signs of allergies, and see if a pattern emerges.

 

For example, if we see a pup only develop signs of itching, scratching, ear infections, etc. in the summer, but by late fall and winter these signs completely go away, a seasonal environmental allergy is most likely and a food allergy is very unlikely.

 

However, if we see a consistent pattern of year-round signs and symptomatic therapy for environmental allergies is only kind of helping or not helping at all, a diet trial would be more important to consider.

 

A year-round environmental allergy to multiple allergens is also possible, but this can be where referral to a dermatologist for allergy testing may be the next best step to discuss.

 

Some unfortunate pups with severe allergy signs, like recurrent skin and ear infections, hair loss, and endless itching and scratching, may have a more serious condition called atopic dermatitis, or atopy. Atopy is considered to be a severe genetic susceptibility to allergens, similar to people with eczema.

 

Atopy is not treated with any new or different methods from the ones we’ve discussed, as many of these dogs can have both food and environmental allergies. But many of them are on multiple methods of therapy at once, sometimes with continued break-through flare-ups a couple of times a year, even in the best-managed cases.

 

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Acute Allergic Reactions

Now we’ll transition into the more serious and sometimes life-threatening types of allergies.

 

In this category, the most common types of reactions are probably to insect bites and stings, and to medications like vaccines.

 

An acute reaction most often happens out of the blue. It occurs usually to something the immune system has seen before, having stored the information away for later. And when later comes, the reaction is a bit of an overreaction.

 

Take an example of a bee sting. Normally a bee sting will cause a small swelling accompanied by some pain and localized inflammation. But it would be abnormal and considered an acute reaction to see the face get swollen, hives develop, and for a pup to experience breathing difficulties.

 

When such a severe reaction does occur, it is called an anaphylactic reaction. Sometimes, on occasion, you can also see a very sudden onset of digestive upset with vomiting and diarrhea in dogs as well.

 

Anaphylactic reactions are the most dangerous, because the entire body is affected by a single, localized exposure to an allergen. Swelling occurs that can eventually close off the airway if left for too long.

 

These usually require immediate veterinary attention. If anaphylaxis is suspected or confirmed, it is common to treat such cases with a fast-acting steroid injection to tell the immune system to back down, accompanied by an antihistamine injection to counteract histamine release.

 

Because these usually happen within 15-20 minutes of exposure, this can either be a blessing or a curse. With vaccine reactions, rare anaphylactic reactions usually occur before the pet leaves the clinic, allowing for immediate treatment.

 

But if something like this occurs out in the woods or at the park, this can certainly be a big concern. Some pets have a history of acute allergic reactions which may prompt a discussion with your vet to have something like an Epipen on hand in the event of something unexpected that needs immediate treatment.

 

But fortunately, anaphylaxis in pets is rare, even more rare than in people. While actual figures are difficult to quote, we’re likely talking about single digit percentages of chance.

 

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Insect Bites and Stings

We’ll get into more specifics here. It’s important to explain why an insect bite or sting reaction is not really considered an “environmental allergy”. The reason is that when an insect bites or stings a pet, the body is reacting to the saliva, venom or toxin that’s been inoculated.

 

This is very different from the immune system responding to pollen or mold. We won’t get into the detailed science of it, but other parts of the immune system additionally come into play.

 

By far the most common allergic bite reaction is to fleas. The main reaction in this case is to flea saliva. The best offense to fleas is with a good defense by using flea preventative products. But an important point to keep in mind is that many products only prevent flea infestations by killing a flea after it bites. Very few products have repellency action.

 

So, some dogs with extreme flea bite hypersensitivity may still have flare-ups when bitten by a flea outside. In these pups, focusing on finding a product that does have repellency may be more important. Discuss these product options with your vet.

 

That leaves us with all other manner of buzzing and crawling creatures like spiders, bees, biting flies, mosquitoes, and others. Bites from these types of creatures most often just cause a localized reaction, but rarely can lead to a hypersensitivity reaction with hives, facial swelling, and breathing difficulty.

 

It’s in these cases where giving an antihistamine can be most beneficial, because histamine is involved more with these types of reactions, while it is rarely if ever involved in most skin allergies in pets.

 

The most common antihistamine to use for these cases is diphenhydramine (Benadryl). If you need it in a pinch, the approximate dosage is 1mg per lb of body weight, but your vet can advise on a more specific dose based on your pup’s weight at the clinic.

 

It’s also extremely important to use the correct and safe form of an antihistamine. The “D” form, which is available for most antihistamine brands, contains pseudoephedrine, which is used as a nasal decongestant for people (hence the “D”). But in pets, pseudoephedrine is a toxic product. Ingestion of it usually requires hospital care. So if you have this form at home, please make sure NOT to give it to your dog.

 

While it may be helpful to give a dose of regular plain benadryl if your pup gets a bee sting, don’t just give a dose and see what happens. Some bite hypersensitivity reactions can get out of control fast, outpacing an oral antihistamine. If you suspect or observe a bite or sting, give benadryl if you have time, but make sure to get your pup to the closest vet as soon as you can.

 

 

Vaccine Reactions

I definitely think vaccines deserve their own short part in this article as their use is very common, considered necessary for some aspects of health, but no less a worry for pet parents.

 

Vaccines work on the principle that if you expose an individual to a weaker form of an antigen, like a virus or bacteria, their body will be able to recognize it for future use by creating antibodies. But in its weakened state, this antigen will not cause the same signs of disease or a significant adverse effect on the immune system.

 

Now, as I’ve already said, immune systems vary. So while most pets that receive vaccines will see no adverse effects at all or at most some mild signs of being tired, a small percentage (again, likely single digit percentages) of pets will have an unexpected, adverse reaction.

 

This type of reaction is usually a delayed hypersensitivity reaction, most often occurring at the time of a booster following the initial vaccine a couple weeks prior.

 

A higher number of pets, though still probably less than 10%, will have some more mild signs that may still indicate an adverse response to a vaccine. This most often includes signs of digestive upset within 24 hours of vaccine administration, which either passes on its own or needs a little supportive care help.

 

Choosing to vaccinate your pet should first and foremost depend on the risk associated with the diseases a vaccine is designed to prevent or lessen the signs of.

 

For example, rabies virus is endemic in our wildlife population meaning any dog, cat, or other mammal, anywhere in the United States, including a person, could be exposed by an infected raccoon, fox, or other mammal.

 

And because the virus is invariably fatal and there is no treatment for it, but the vaccine is nearly 100% effective at preventing it, the benefit of vaccinating is considered to be far greater than a low risk of a possible adverse reaction to the vaccine.

 

And because our pets are more likely to run into a rabid animal, and it’s impractical to vaccinate all people, we also vaccinate pets as a way of protecting the human population.

 

But contrast this necessary vaccine with the one for Lyme disease spread by ticks. If you look at prevalence maps provided by the Companion Animal Parasite Council, Lyme prevalence is very high in some states, but pretty low in others. In Washington State, less than 1% of dogs tested were positive. But in Vermont, 15% of dogs tested were positive.

 

It’s far more common for Lyme vaccination to be heavily recommended on the east coast because of how often we see it. But in the pacific northwest, this may be more of a counseled decision.

 

When it comes to vaccines, always make sure to discuss the pros and cons with your veterinarian. With some pups who have a history of allergic reactions, it may be best to avoid vaccines for diseases where the risk is considered low.

 

But for higher risk diseases, we may decide to pre-medicate with an antihistamine beforehand to make sure the disease is still protected against, while modulating any adverse effects the vaccine may cause.

 

Other Medications

Reactions to other medications, including heartworm, flea, and tick preventatives are also very uncommon.

 

Adverse effects and reactions can vary widely, but all of the possibilities are typically listed, along with all clinical trial and testing information, on the information data sheet that is required to be available for every product. Most can be found online as a separate PDF document page, or as an insert with the medication's packaging.

 

We address adverse reactions to medications similarly to vaccine reactions. We carefully weigh the necessity of using the product with the costs of not using it at all. There may also be other similar, alternative drugs to consider. This is especially the case with antibiotics, parasite preventatives, and anti-inflammatories.

 

Lastly, it’s important to keep in mind that with drugs, not all adverse effects are really true allergic reactions. This is kind of similar to the difference between food intolerance and a food allergy.

 

An antibiotic, for example, may cause diarrhea because it has upset the delicate bacterial balance in the GI tract. This isn’t an allergic reaction, but an uncommon consequence of using a broad-spectrum medication. In this case, we might stop the antibiotic, but if we’re dealing with a bad infection and need to continue it, we might try to address the side effects separately until the medication course can be finished.

 

Allergies: Annoying, But a Part of Life

There’s probably a lot more details we could discuss about allergies in pets, but this covers the main points.

 

Severe allergies are fortunately rare, but even the mildest forms can be an annoying nuisance for you and your pooch.

 

Allergic responses vary quite a lot from pet to pet, just as they do from person to person. So always make sure to discuss concerns about your pet’s specific allergy condition with your veterinarian, to make sure there is a catered and personalized plan for your pup.

 

Topics: Pet Health

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