Scratching, sneezing, hives, diarrhea—these might be signs that your dog has an allergy. But because other health issues can produce these same symptoms, diagnosing allergies can be tricky. Learn about common allergies in dogs, how to figure out what’s causing a particular reaction, and what you can do to help.

An allergy is an exaggerated, abnormal immune response to something benign that the immune system misinterprets as a threat. The substance that triggers this abnormal immune response is called an allergen, which can be inhaled, touched, or eaten.

When it’s functioning properly, the immune system keeps a dog healthy by detecting harmful intruders (like pathogens and parasites) and attacking them before they can cause infection or disease. But in some dogs, the immune system has a problem called atopy, which is a predisposition to overreact to certain allergens as though they were dangerous invaders.

Allergies can cause a wide range of symptoms, many of which can also be caused by other, non-allergy conditions. That’s why it may take time and effort to figure out what’s causing your dog’s symptoms.
Here are some of the most common dog allergy symptoms:

• itchy skin, ears, or paws
• hair loss
• hives
• swelling of the face, ears, lips, eyelids, or earflaps
• red, inflamed skin
• saliva staining
• darkening and/or thickening of the skin
• recurrent skin infections, including chin acne
• recurrent ear infections
• sneezing
• itchy, watery eyes
• runny nose
• vomiting
• diarrhea

Reactions can be triggered by a wide variety of dog allergens. Some are inhaled (like pollen), others are substances that come into direct contact with the skin (like certain plants and medications), and others are ingested (foods). Here are some of the most common types of allergies affecting dogs.

The most common allergy in dogs is a hypersensitivity to flea saliva, which causes the immune system to have an extreme response to flea bites. A flea bite allergy can cause intense itching, redness, irritated skin, and hair loss. This reaction is referred to as flea allergy dermatitis.

Allergic reactions to certain environmental factors are also very common in dogs. Bites from insects other than fleas (like mosquitoes) can cause hypersensitivity responses. Some dogs are allergic to bee stings.

Airborne particles that are common allergy triggers for dogs include house dust mites, pet dander (shed skin cells) from other animals, plant and tree pollens, and mold spores.

Direct contact with certain substances—including particular plants, plastics (in toys or food bowls), chemicals, and medications—can also cause allergic responses. Itching is the most common symptom of environmental allergies.

Like human allergies, dog allergies can be seasonal. Maybe you’ve noticed that your dog itches more in the spring and summer, or sneezes a lot in the fall. Those are useful clues: plant pollens and insects, for example, are more prevalent in the warmer months, while mold is more common when the season is cool and damp.

Atopic dermatitis in dogs is a chronic itchy skin condition caused by hypersensitivity to one or more allergens. This skin disorder is classified as an allergic condition because it is associated with excessive immunoglobulin E (IgE) production in response to particular allergens, which may be inhaled, touched, or eaten. Atopic dermatitis is fairly common, occurring in roughly 10%–15% of all dogs. (Certain dog breeds may be more likely to develop this condition.)

Food allergies are less common in dogs than airborne allergies; they’re also less common than food sensitivities (which we’ll talk about next). But some dogs do have allergic reactions to one or more ingredients in their diet. The symptoms—including itching, irritated skin, and hives—can look just like those of other allergies, but they don’t vary with the seasons.

A true food allergy involves an immune system response: the body’s immune cells attack certain food molecules, mistaking them for dangerous invaders. The large majority of food allergies in dogs are to a protein source the dog has been eating for a long time. A food sensitivity, on the other hand, does not involve the immune system. It’s simply an inability to digest a particular food or ingredient. Lactose intolerance is a familiar example of a food sensitivity: if a dog doesn’t have enough of the enzyme lactase, which is necessary to break down the lactose (a sugar) found in dairy products, then eating dairy will usually be followed shortly by bloating, flatulence, and/or diarrhea. That’s because the dog’s digestive system can’t process dairy correctly.
In dogs, food sensitivities are much more common than true food allergies, which occur in only 1%–2% of all dogs.

Itchy skin and sneezing fits are not symptoms that scream ‘gut health’, but allergies and your dog’s gut microbiome are connected in multiple ways. 

For starters, the gut microbiome houses most of the immune system: 70%–80% of your dog’s immune cells live in the gut and ‘communicate’ with gut bacteria. When the gut’s microbial populations are out of balance, immune functions stop working properly, making allergic reactions more likely.

Another result of an imbalanced gut microbiome is increased permeability of the gut lining (a problem sometimes referred to as “leaky gut”). When the gut lining isn’t healthy enough to serve as a strong barrier between the digestive tract and the rest of the body, food molecules can escape from the intestines into the bloodstream. There they can be misidentified and attacked as invaders by the immune system, leading to a hyper-reactive cycle in which the immune system becomes sensitized to those substances and overreacts every time it encounters them.

Studies have found an association between gut microbiome imbalance and atopic disorders in both humans and animals. When the gut microbiome has too many bacteria from groups that are involved in an inflammatory response, that imbalance leads to unhealthy levels of inflammation, which can trigger extreme immune responses throughout the body.

The good news is that the gut microbiome’s involvement in allergies means that we may be able to resolve an allergy by healing the gut. For example, treatments for atopic dermatitis that target the gut include probiotics and fecal microbiota transplant (FMT). FMT is a promising treatment for allergy and immune conditions in dogs that can resolve the root cause. It is far safer than pet allergy medications that come with unwanted side effects. 

Learn more about FMT in an oral capsule.

Figuring out the root cause of allergies may not be easy. For one thing, all the symptoms that can be caused by allergies can also be caused by other health conditions. So your veterinarian may want to test your dog for some of those other issues to rule them out.

To complicate matters, hypersensitivity reactions fall into several types. What most people think of as the “classic” allergic reaction occurs within seconds or minutes of exposure to the trigger, such as swelling after an insect bite. But other types of reactions take two or three days to produce full-blown effects, such as hives in response to a food allergen.

If your dog is having a severe allergic reaction, you should seek help immediately. But in most cases, allergy symptoms are not life-threatening and there is a lot you can do to help your dog feel better.

Your veterinarian is a great resource for getting to the bottom of diagnosing and managing your dog’s allergies. 

Here are some topics that you should be prepared to discuss:

• Flea mitigation and treatment. 
• Your dog’s diet. They may recommend a prescription diet, or a diet trial for suspected food allergies.
• Minimizing allergens from your dog’s environment. You may need to keep your dog indoors more when pollen levels are high, vacuum more, or use a HEPA air filter. 

Here are some common treatments they may recommend:

• Immunotherapy (a series of “allergy shots” to desensitize the immune system to a particular allergen)
• An over-the-counter antihistamine (to counteract the immune overreaction)
• Steroids or corticosteroids (to relieve itchiness and irritation)
• Antibiotics (if your dog’s skin has a secondary bacterial infection)
• Therapeutic shampoo to manage skin inflammation

The health of the trillions of bacteria that live along your dog’s digestive tract is directly linked to your dog’s diet. And because gut bacteria are connected to your dog’s immune function, diet is a great way to manage allergies and inflammation. 

Current research suggests that the best diet for your dog’s gut health is high in protein, fiber, fatty acids (which have anti-inflammatory properties), and lower in carbohydrates. 
While no food is truly “hypoallergenic,” some dogs can benefit from commercially available hydrolyzed diets—in which the animal protein has been broken down into molecules small enough that they are unlikely to cause an immune response. And a rotational diet can help prevent future food sensitivities or food allergies by limiting your dog’s exposure to the same ingredients over time.

Gut Microbiome Testing can give you important clues about what might be causing your dog’s symptoms. For example, the DoggyBiome Gut Health Test can detect bacterial imbalances and identify problematic groups of bacteria associated with inflammation and allergic conditions.
For example, high levels of Sutterella bacteria in the gut microbiome are associated with food sensitivities. Oscillospira bacteria tend to be deficient or absent in pets with severe food allergies. Clostridiales bacteria are known to play a role in preventing “leaky gut syndrome” and are often missing in a dog with allergies. There is even some evidence that introducing Clostridiales (via FMT) can decrease or resolve allergic symptoms.

A fecal microbiota transplant (FMT), also called a fecal transplant, is a way to transfer a complete and balanced community of gut microbes from a healthy donor to a sick recipient. A large body of scientific research has shown that FMT can resolve a variety of symptoms associated with imbalance or dysfunction of the gut microbiome, including various immune system issues, skin problems like atopic dermatitis, and digestive disorders like inflammatory bowel disease (IBD).

If your dog is missing important beneficial bacteria—for instance, after a course of antibiotics—FMT can fill in those missing groups, restoring balance to the microbiome and strengthening its immune functions. 
Some veterinarians can perform a fecal transplant procedure via an enema or nasogastric tube. However, the expense and risks associated with the required sedation aren’t ideal for many pet parents. Luckily oral FMT capsules, like DoggyBiome Gut Restore Supplement, are just as effective.

You can provide allergy relief to your dog by improving their immune health. Biotic supplements are a worthwhile addition to your dog’s diet to improve their immune health by way of gut flora. Prebiotics, like those found in DoggyBiome™ Gut Cleanse Powder, feed beneficial bacteria. Probiotics, like those found in DoggyBiome™ S. boulardii + FOS Powder, improve immune function by releasing anti-inflammatory molecules in the gut. Postbiotics, like those found in the delicious DoggyBiome Skin & Coat Shield Chews, introduce important molecules for proper immune system function. 

Learn more about the benefits of biotic supplements here.

What are common allergies in our area that you see in other dogs? And how can I reduce my dog’s exposure to them?

Do you recommend allergy testing for my dog and what type do you recommend?

Do you recommend that I switch my dog’s food? 

If I want to avoid medication, what other options do you suggest? 

I heard that prebiotics, probiotics, postbiotics, and fecal transplants can help improve my dog’s allergies. What are your thoughts about this?