Allergies in Dogs | Symptoms, Treatment and Prevention

Allergies in dogs happen when their immune system overreacts to a threat (whether it is from an external or internal source). Even though allergies are more and more common, they can be somewhat difficult to diagnose and treat. In this article, we’ll look at the types of allergies that dogs can suffer from, their causes, their symptoms, treatment, as well as how you can prevent them in the long run.

Types of Allergies in Dogs

There are four major types of allergies in dogs that you should know about. Sure, an allergy can take many different forms, depending on the dog breed, age, and the variety of other health problems that the animal is experiencing. However, in general, allergic reactions are part of the following categories.

  • Allergies caused by fleas and other parasites
  • Allergies caused by food
  • Contact allergies
  • Environmental allergies

Those that are caused by external parasites are in fact caused by their saliva, which contains an enzyme that makes it easier for them to suck on the dog’s blood. Flea bite hypersensitivity can cause discomfort and intense itching. This is known as flea bite dermatitis. Some of the symptoms that you’ll notice in a dog that has this issue range from excessive licking and scratching, hair loss, and the formation of skin lesions and scabs. The diagnosis of this type of allergy is usually easy as either yourself or the vet will determine whether there are any parasites on your pet’s skin. Treatment involves the use of any method that can remove the parasites, whether it consists of grooming or topical medicine. Some dogs have to be prescribed antihistamines or anti-inflammatories to deal with the excessive itching.

Food allergies can be developed at any age and they can occur because of any protein or carbohydrate component in the food. Antihistamines and corticosteroids aren’t very effective for this issue – in fact, they don’t solve the problem, they merely make the symptoms a little milder. Vets typically recommend an elimination diet, which involves cutting out ingredients one at a time. Once the allergen is eliminated, a new diet is prescribed and the dog’s condition improves considerably.

Contact allergies happen when the dog’s skin comes into contact with a material or substance (such as one that’s present in flea treatments or shampoos). Some dogs develop allergies to materials such as wool. In this case, the dog gets dermatitis usually in the form of itching. The most important thing to know about this kind of allergy is that the dog develops the skin problem in the area that the allergen touched. Contact allergies are significantly less common compared to the others, but they can still be challenging as you need to discover what’s triggering the allergic reaction.

Environmental allergies can be seasonal or can happen when a dog has inhaled an allergen from the air. This type of condition is also known as atopic dermatitis as it doesn’t relate to an allergen that you can see and remove (as would be the case of allergies that are developed to flea bites). Dogs can develop environmental allergies to pollen or to specific plants that grow at specific times of the year, but they can also suffer from this issue year-round due to the presence of mold or mildew in their living environments.

Types of External Parasites That Cause Allergies

Some of the most common parasites that cause allergies in dogs are fleas, mites, and ticks. Dogs can develop skin conditions to dust mites, and they are somewhat problematic as they feed on the dog’s skin and dead hair. In case you didn’t know, dogs aren’t allergic to the parasites themselves — instead, they develop allergic reactions to the protein present in the feces of the mites.

As we might have mentioned, dogs don’t develop allergies to fleas, but they do to their saliva. The difference between a dog that has fleas and scratches on occasion and doesn’t have an allergy and one that suffers from one is that the scratching is incessant in the case of the second. Some dogs experience such severe itching that they will cause skin lesions all by themselves.

Allergies to ticks are a little less common compared to those to fleas, but they can still happen. Again, the issue is the tick’s saliva, not the bite itself. Plus, ticks have a nasty habit of attaching to some parts of the canine’s body that he or she can’t reach, so they are even more frustrating. Ticks are extremely dangerous as they are vectors of Lyme Disease and babesiosis, both of which can cause anemia, icterus, and a variety of other health problems.

Atopic dermatitis

Atopy is usually synonymous with a dog having an inhalant allergy. Dogs can develop allergies to tree pollen, weed pollen, grass pollen, mildew, mold, and other allergens. Humans can be allergic to these, too, but their symptoms differ from what you’d see in a dog that has the same issue. While we get runny noses, runny eyes, and sneezing, dogs develop itchy skin.

Unfortunately, most cases of atopic dermatitis can’t be treated as there is no permanent cure for them. Their symptoms can be controlled, however. Dogs with inhalant allergy begin showing the signs when they are 1 to 3 years old. Diagnosing atopy can be rather difficult, but sometimes skin testing and blood tests can prove to be effective in this sense.

Treatment, in this situation, consists of alleviating the clinical signs and involves the use of anti-inflammatories, shampoo therapy, and desensitization therapy.

Anti-inflammatories are most effective when they are paired with fatty acid supplementation (omega-3, for example) as these are known to improve the body’s response to antihistamines or steroids. Some modern drugs, such as cyclosporine, can also be quite beneficial in treating atopy as they have a reduced number of side effects, especially when compared to corticosteroids.

Pet parents can use a hypoallergenic shampoo to soothe the dog’s inflamed and itchy skin. Although the general opinion is a little confusing in this sense, it is widely known that dogs shouldn’t take baths more often than every 2 weeks as doing so would affect their natural sebum secretion. Sebum is important as it acts as a protective layer on the skin.

Desensitization or hyposensitization therapy is also available and it involves using specific antigens that were identified following allergy testing. In this particular case, the dog gets regular allergy shots on a weekly or bi-monthly basis. This treatment has variable success rates, but it is estimated that about a quarter of the dogs undergoing it experience an improvement in their clinical signs. What this means, in turn, is that steroids are less necessary in their case either in terms of their amount or frequency of administration. Your vet can provide you with training so that you can learn how to administer the allergy shots yourself, without needing the assistance of a medical professional. This would be useful for a dog that basically needs to be treated for his entire life.

Unfortunately, atopic dermatitis is considered a lifelong disease that calls for regular veterinary examinations and long-term management.


Despite its name, ringworm isn’t a condition caused by internal parasites. It is, in fact, a fungal infection that’s considered a zoonosis as it can be transmitted from dogs to humans or the other way around. The symptoms of this health problem are itching and patchy hair loss, with the lesions being located on the dog’s head, ears, and forelegs. The hair loss patches can be particularly helpful in differentiating this fungal infection from a flea bite allergy.


Hotspots are known as a form of moist dermatitis in dogs. The skin can be inflamed, red, and irritated, and the spots can be developed as a result of a flea bite or other allergic reactions. Unfortunately, bacterial complications are quite common, as well as hair loss.

Some of the symptoms of hotspots in dogs are the following:

  • Red, irritated skin lesions
  • The affected area is hot to the touch
  • Itchiness
  • Chewing at the site
  • Yellow scabs around or on the skin lesion
  • Moist and matted fur
  • Hair loss and a foul odor at the site
  • Potential aggression if you try to touch the area (as the hotspots are sore)

Hotspots have several causes that range from flea allergies or local cuts to ear infections or anal gland infections that can make the dog scratch those body regions until he himself causes the hotspot. While it is true that they are commonly caused by insect bites, one shouldn’t overrule the possibility that the dog’s behavior is at the root of the problem. Hotspots can also be encountered in dogs that are bored or stressed and that lick or bite their skin as a way of soothing themselves.

Food Allergies

Over the years, food allergies have become more common compared to airborne allergies or those developed to insect bites. Any breed can develop a dog food allergy, but many studies suggest that they are more frequent in West Highland White Terriers, Labrador Retrievers, as well as Cocker Spaniels. The age of onset varies from one animal to the next or depending on the specific moment when the allergen has been introduced into Fido’s diet.

As we have mentioned at the beginning of the article, food allergies are diagnosed by feeding a limited diet. In this particular situation, skin and blood tests aren’t reliable. The test plan should be developed by your vet and yourself and the elimination diet needs to be balanced, as well as nutritionally complete. Ideally, it shouldn’t contain any of the ingredients that were previously fed to the dog.

A prescription diet containing hydrolyzed proteins is also available as these can be broken down into components that the dog’s body doesn’t recognize. No matter what diet is chosen, pet parents have to be completely aware of the fact that their canine friend should only eat the food and treats that were prescribed to them. Otherwise, the diet will be considered a failure.

Trial diets are usually fed for up to three months. If the dog experiences a complete or significant resolution in the clinical signs, the elimination diet worked and the diagnosis of food allergy is considered correct.

The foods that dogs can be allergic to include:

  • Beef, chicken, eggs
  • Corn
  • Wheat
  • Soy
  • Milk

Although less common, food allergies can also be developed as a dog gets older. This also happens in humans, with people developing food sensitivities as their immune systems become less effective at fighting the aggression of allergens.

Commercial Dog Food and Food Intolerances and Allergies

There are several issues with commercial dog food and we’re going to try our best at explaining them below. Most foods contain food dye, ‘meat by-products’, corn and corn gluten meal, and even antifreeze.

Food dye is used because color diversity appeals to pet parents — but it doesn’t do the same for dogs. Many food brands have kibble that’s shaped or colored like peas or carrots, but the truth is that the veggie content in most food varieties is quite low. Dog food can contain dyes such as Red 40 or Yellow 6, both of which have been linked to cases of cancer. As you might have guessed, some of the artificial colors and preservatives present in commercial dog food are also linked to cases of allergies.

Corn causes medical problems such as gas and bloating, acid buildup, and ulcers, and some dogs are specifically allergic to corn and corn gluten meal. While it’s true that meat by-products pose less of a danger in terms of allergies, they aren’t the best ingredient to include in a dog’s healthy diet. Meat by-products typically mean internal organs, fat, blood, animal heads and feet, but also feathers and even animal fetuses.

Last, but not least, antifreeze is sometimes added to dog kibble as it can preserve its moisture. It also makes it palatable. When it is ingested in large amounts, antifreeze can cause renal failure, but its toxicity is relevant for when your dog is fed small amounts every single day.

Homemade, cooked, and raw diets are far healthier by comparison. They don’t contain any artificial fillers, no antifreeze, no dyes, and it is all up to you to use the right ingredients and avoid potential allergens like wheat, soy, or corn.


Anaphylaxis is a severe allergic reaction that can lead to anaphylactic shock, where respiratory and cardiac failure is to be expected, and worse, death. The reaction typically involves the shut down of major organs, but it can also be localized (rarely). Unfortunately, almost any substance can cause an allergic reaction in your canine companion, and that’s what makes anaphylaxis so unpredictable.


  • Wheezing and difficulty breathing
  • Pale gums
  • Cold limbs
  • Increased heart rate and a weak pulse
  • Excessive salivation
  • Vomiting and/or diarrhea
  • Seizures
  • Shock
  • Coma

Cases of anaphylaxis that are more localized and less extreme have less severe clinical signs, but they still call for veterinary care and they can still lead to anaphylactic shock if the dog gets exposed to the allergen again.

Here are some symptoms of a less intense allergic reaction:

  • Difficulty breathing or a dry cough
  • Vomiting after eating some types of foods
  • Bumps, rashes, swelling, hives, or itchy areas
  • Congestion

Bee sting reactions:

  • Trouble breathing
  • A bluish tint to the dog’s skin
  • Wheezing
  • Collapse

What Causes Anaphylaxis in Dogs?

  • Food or chemicals in food
  • Medication or vaccines
  • Insect stings or bites


Anaphylaxis is a medical emergency, so stabilizing your dog is paramount. In cases of anaphylactic shock, an adrenaline injection is usually necessary, along with the administration of hydrocortisone and antihistamines to keep the allergic reaction under control. Depending on the severity, the dog may also require intravenous fluid to avoid a drop in blood pressure, as well as oxygen. The pet is then closely monitored for a day or two following the treatment.

If your dog has had an allergic reaction to a medication or a vaccine shot, this is important information that should be written down in the dog’s medical file. Even if you move to another area of the country, you should tell your new vet what past reactions your dog had. Thanks to this info, the vet will choose a different type of vaccine or medication — not the one that could make your dog go into anaphylactic shock.

If your dog has had problems with insect bites before, it would be best to ask your vet to give you an epinephrine syringe that you can carry with you and that effectively neutralizes the allergic reaction in case your dog comes into contact with the allergen again. Going to see the vet is still necessary even if the epinephrine injection was effective.

How Are Allergies Generally Diagnosed?

Of all of the medical conditions that a dog might suffer from during his or her lifetime, allergies are by far the hardest to diagnose (especially atopic dermatitis). While it can be tricky, veterinarians could use various types of allergy testing to find the specific allergen depending on what’s suspected and based on the dog’s reaction. It is important to note that allergic reactions differ from one dog to the next and they depend on the pet’s lifestyle, breed, and even his or her age.

Pin-prick tests and blood tests could be useful, too, as they can be utilized to narrow down the potential environmental allergens. Parasitic allergens can be identified on the dog’s coat. For pets that have scabies, collecting a very small sample of their skin could be useful as the vet could examine it under the microscope.

As we have mentioned already, food allergies are usually discovered thanks to an elimination diet.

Treating Allergies in Dogs

An allergy is not a medical condition per se, and what we mean by this is that it’s not as straightforward as an infection caused by a specific pathogen which if you would kill, you’d effectively get rid of the infection, too. The allergy is an immune response, not a disease. Removing the allergen is the right way of going about things, but as you can expect, this can be very complicated.

There are several different treatments available for the symptoms of allergies, but these do not solve the direct cause. Benadryl was an antihistamine used for years for alleviating the clinical symptoms of dog allergies, and so is Zyrtec (cetirizine). Benadryl has the drawback of making dogs drowsy, which is why it is sometimes recommended for stress and anxiety, but Zyrtec doesn’t have the same side effect.

Other allergy medications include Chlorpheniramine (also used in people) and Hydroxyzine, which are antihistamines. Supplementing your dog’s diet with Omega-3 fatty acid works in synergy with steroids and antihistamines and is considered a good way of reducing allergy symptoms. Omega-3 is, in fact, excellent for preventing a wide array of health problems, so giving it to your dog preventively would be a great idea.

Preventing allergies in dogs

From choosing the right dog food to preventing fleas, there are several things that you can do to make allergies less possible. Healthy dog food, especially for pooches that have had allergy-related problems in the past, should contain a novel protein such as duck, venison, or fish. That’s because beef and chicken are common food allergens, so even feeding your dog kibble made from lamb can make a difference, even though it’s not the lightest (calorie-wise) option of all. Natural or grain-free diets are best, and raw and homemade cooked food are two other choices to consider.

Bathing your dog on a regular basis can help remove some of the microscopic allergens that remain on his or her coat and skin. Medicated shampoos are also available, especially for serious skin issues, but in any case, avoid bathing your dog too often as this removes the sebum and leaves your dog’s skin without any natural protection.

Since many dogs suffer from flea bite allergies, flea prevention should be a major part of responsible pet parenthood. Fleas are more active and common when it’s warm outside, so make sure you use preventive flea medication (whether topical or internal) from the beginning of spring to the end of autumn.

Keeping your dog’s living environment clean is another way of going about things as some dogs can develop allergies to dust mites, mold, or mildew. Be sure to use natural cleaning products to avoid causing your dog to experience respiratory problems.

If your dog’s skin is itchy, you could try to use essential oils to alleviate some of the symptoms. We’ve written an extensive article on this topic before, and it’s true that some essential oils such as basil, ginger, and rosemary can be excellent anti-inflammatories. However, you should never use them undiluted as you could effectively burn Fido’s skin. Other oils that can soothe skin reactions are chamomile, lavender, as well as peppermint, and lemongrass and citronella can help keep insects at bay.

Final thoughts

Did you know that almost 25% of all dogs will develop an allergy at one point in their lives? Out of these, it is estimated that up to 15% are related to food, but the vast majority of allergic reactions are caused by environmental allergens. Dogs can have several allergies at once, and this can make the diagnosis quite challenging. For example, your pooch could have an allergy to gluten, but also have one to flea bites.

An ounce of prevention is worth a pound of cure, so always make sure you pay attention to your dog’s behavior every day to notice if anything changes.



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