Allergic reaction manifestation varies with the type of allergen, the causative agent, and the individual dog’s immune response.  There are two categories of reactions: cutaneous and non-cutaneous reactions.  Environmental factors such as the season, location of the residence (urban or rural), and the onset and duration of allergic reactions will be discussed in this article.

Cutaneous allergies in dogs refer to allergic reactions that primarily affect the skin. Various allergens can cause these allergies, and they often lead to skin-related clinical signs and discomfort in affected dogs.

Atopic dermatitis is a common allergic skin condition in dogs. It is typically associated with environmental allergens such as pollen, mold, dust mites, and certain grasses. Dogs with atopic dermatitis may exhibit itching, redness, inflamed skin, and recurrent ear infections.

Some dogs can develop allergies to specific ingredients in their diet. Commonly reported food allergens for dogs include animal proteins, such as beef and chicken, grains, and artificial additives. Food allergies can cause skin issues like itching, redness, hives, and gastrointestinal symptoms such as vomiting and diarrhea.

Contact dermatitis can also affect dogs when a dog's skin comes into direct contact with substances that trigger an allergic reaction. Common irritants include specific plants, cleaning products, grooming products, or materials the dog comes into contact with regularly. Clinical signs may include redness, itching, and sometimes localized swelling.

An allergic reaction caused by fleas causes flea allergy dermatitis (FAD). Dogs can react severely to a flea bite, causing intense itching, redness, and hair loss. Dogs with FAD are often hypersensitive to flea saliva.

Clinical Signs of Cutaneous Allergies in Dogs

The general clinical signs of cutaneous allergies are inflammation, itching (pruritus), redness, hair loss, and secondary skin infections. The clinical signs of cutaneous allergic reactions depend on the location of the body. 

On the paws, you will notice a yeasty odor, redness, moisture, and swelling or hardening of the footpads. If your dog is constantly licking and chewing on the paws, she is experiencing pruritus (itchy skin). 

A yeasty smell is usually present when the ears are affected by allergies. The ear flap is often red, moist, greasy, and swollen. A dark, odorous discharge can occur in the ear canal.

Skin issues related to allergies present as oily, dry, or flaky skin. The yeasty smell is again typical. Fur loss and infected areas, usually referred to as hot spots, are often present. Acute allergic reactions, those with a sudden onset, can cause hives or rashes.

Allergic reactions can also occur in your dog’s mouth. Foul breath odor, red and swollen gums, tartar accumulation, and sores on the mouth and the tongue can all indicate an allergic reaction to a food or other substance your dog is chewing. The sudden onset of panting with excessive drooling can also be caused by your dog encountering an allergen.

Swollen eyelids, watery, weepy eyes, drainage in the inner corners of the eyes, and redness indicate that your dog’s eyes are reacting to an allergen. Dogs will rub their face on furniture or carpeting to relieve some of the itchiness.

What are Non-Cutaneous Allergies Reactions in Dogs?

Non-cutaneous allergic reactions in dogs involve responses to allergens that affect areas beyond the skin. These reactions can manifest in various body systems, and the severity can range from mild to severe. Non-cutaneous allergic reactions can occur in the respiratory and gastrointestinal system. Anaphylaxis, a severe systemic reaction to insect bites, vaccinations, or medications, is another type of non-cutaneous allergic response.

Dogs can be allergic to environmental factors such as pollen, dust mites, mold spores, and certain types of grasses. Inhalation of these allergens can lead to respiratory symptoms. Exposure to smoke, air pollution, gas fumes, or other respiratory irritants may trigger allergic reactions in some dogs, leading to coughing, sneezing, and difficulty breathing.

In addition to causing skin issues, food allergies can also manifest with gastrointestinal clinical signs. Dogs may experience vomiting, diarrhea, flatulence, and abdominal discomfort due to allergic reactions to specific ingredients in their diet.

In severe cases, dogs can experience anaphylaxis, a life-threatening systemic allergic reaction. Anaphylaxis can occur rapidly after exposure to an allergen, and clinical signs may include difficulty breathing, swelling of the face and throat, vomiting, diarrhea, and collapse. Anaphylaxis requires immediate emergency veterinary attention.

Clinical Signs of Non-cutaneous Allergic Reactions 

Non-cutaneous allergic reactions are those that occur within your dog’s digestive tract. These are often associated with responses to food ingredients. Excessive gas, oily stools with mucous, dark, bloody stools, diarrhea, and vomiting or regurgitation of undigested food are clinical signs of non-cutaneous allergic reactions.

Common allergens triggering an anaphylactic reaction include vaccinations, bee or wasp stings, and medications. Clinical signs of anaphylaxis include swelling, hives, and difficulty breathing, which can lead to death if not treated promptly.

The term “hygiene hypothesis” was introduced in 1989 in humans but is equally applicable to dogs.  It was observed that early childhood exposure to specific microorganisms found in nature protects against allergic diseases by contributing to the development of the immune system. A lack of exposure leads to defects in establishing immune tolerance.

The Hygiene Hypothesis suggests that reduced exposure to various microorganisms during a dog's early development may increase the risk of specific health issues, including allergies and autoimmune conditions. The period for exposure for dogs begins in utero and continues through puppyhood. 

In the context of dogs, the Hygiene Hypothesis proposes that dogs that grow up in overly sanitized and clean environments with limited exposure to diverse microbes may have a less well-balanced immune system. The lack of exposure to a diverse range of microorganisms, such as bacteria and parasites, during a dog's early life may impact the proper education and development of the immune system.

The hypothesis suggests that dogs that do not encounter a variety of microbes early in life may be more susceptible to developing allergies and autoimmune diseases where the immune system mistakenly targets the body's own tissues.

To assist the veterinarian in making a definitive diagnosis of an allergic reaction, you need to define the onset and duration of your dog’s condition. There are four categories: acute or sudden onset allergies, chronic long-term allergies, recurrent or seasonal allergies, and the genetically predisposed disease - Canine Atopic Dermatitis (CAD).

You may have heard of an acute reaction referred to as anaphylaxis. Anaphylaxis is a severe reaction that can develop within an hour or even minutes or seconds of exposure to an allergen that is either systemic (throughout the body) or localized to one specific area. Anaphylaxis triggers can include foods, medications, and insect stings. 

Clinical signs of a systemic reaction include vomiting, diarrhea, pale mucous membranes in the mouth and around the eyes, cold limbs, excessive salivating or drooling, wheezing and difficulty breathing, increased heart rate or a weak pulse, seizures, or coma. 

A localized reaction would cause hives, swelling, bumps, rashes, or itchy areas. An acute systemic reaction or anaphylactic reaction can be a life-threatening situation that requires immediate veterinary care. 

A chronic allergy is a long-term problem that is very difficult to resolve. Chronic conditions associated with allergies are inflammation, alopecia (hair loss), pruritis (itchy skin), scaly or greasy skin, and pyodermatitis caused by yeast, fungus, or bacteria.

Your dog’s immune system overreacts to grasses, trees, or weeds in the environment, usually during spring, summer, or fall when certain plants pollinate. Clinical signs of seasonal allergies can include pruritus with secondary skin lesions caused by self-trauma, such as chewing or licking the paws, rubbing the face, and scratching the area. Conjunctivitis, sneezing, and respiratory signs can also be present.

CAD is an incurable inflammatory and pruritic skin disease in dogs with a genetic component. CAD causes moderate to severe skin conditions that are very difficult to cure.  

The most common breeds affected by CAD are the Labrador Retriever, Golden Retriever, Boxer, English Bulldog, French Bulldog, German Shepherd, Dalmatian, American Cocker Spaniel, and the West Highland Terrier. 

Seasonal, flea, house dust mites, and other contact allergies account for many of these dogs’ clinical signs. In contrast, food sensitivity was seen in less than 7% of the dogs evaluated.

Your dog’s primary residence and the percentage of time spent outside can impact the development of allergies. 

Dogs raised in urban environments with little to no time spent in forests or other natural areas have a higher incidence of allergies. Diesel fumes are a contributing factor. 

Environmental conditions that decrease CAD include being born in the owner’s household and coexistence with other dogs. Based on the hygiene hypothesis, the home’s cleanliness causes an increase in CAD.

An immediate allergic reaction to a vaccine would include the development of hives, swelling of the muzzle, and, in severe cases, anaphylactic shock. These reactions require immediate veterinary care.

A delayed reaction, usually within 24 hours post-vaccination, is typically a swollen, painful lump at the injection spot. Although usually not a severe condition, it should be brought to your veterinarian’s attention if it does not resolve within 3-4 days.

Veterinarians have a variety of prescription medications to treat your dog for allergies. However, there are many natural remedies  and changes in routines to assist you with managing your dog’s allergies. 

A balanced and species-appropriate diet will support your dog's immune system and reduce inflammation and itchiness.  An appropriate diet would include high-quality proteins, healthy fats, natural antifungal foods, prebiotics, probiotics, organ meats, and fiber from low-glycemic fruits and vegetables or fur. The Real 6X Ancestral Diet™  or the Real Ancestral Diet, contains the ideal ingredients to support your dog’s immune system, skin, and gut microbiome.

The gut microbiome is likely imbalanced if your dog is prone to allergies that manifest as skin infections. Incorporating probiotics (beneficial bacteria) and prebiotics  (fibers that nourish beneficial bacteria) can help restore a balanced gut environment. 

Beneficial supplements such as quercetin, herbal teas, omega-3 fatty acids, and essential oils can also relieve your dog’s allergies. 

Quercetin  is a flavonoid that is naturally found in fruits and vegetables. Its unique biological properties have been shown to improve mental and physical performance, reduce the risk of infection and disease, and act as an anti-inflammatory, anti-carcinogen, anti-viral, and antioxidant. 

Chamomile, green tea, calendula, and black tea can cool irritated and sensitive skin. Cooled tea bags can be used directly on irritated skin, or cooled brewed tea can be put in a spray bottle and applied to the skin.

Processed dog food often contains too much Omega-6, which alters the ideal ratio of Omega-3 to Omega-6 in your dog’s diet. An imbalance in the fatty acids leads to inflammation. Omega-3 fatty acids improve the skin barrier to external pollen and irritants while reducing inflammation.  

Lavender, chamomile, and peppermint oil all calm irritated red skin. Myrrh helps to repair damaged skin. It has analgesic properties that can reduce pain associated with severe skin disorders and self-induced damage caused by scratching.

Allergies in Dogs: Environmental Factors and Clinical Signs

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