Dog Allergy Symptom Identifier
Identify possible allergy types from your dog's symptoms. Get an evidence-based assessment with next steps for your vet visit.
Assessment Results
Select symptoms on the left to see your dog's allergy assessment. Results update automatically as you check symptoms.
Understanding Dog Allergies
Canine allergic skin disease is one of the most common health concerns in dogs, with atopic dermatitis alone affecting an estimated 10–15% of the dog population according to Cornell University College of Veterinary Medicine. Allergic skin disease is one of the most frequent reasons for veterinary visits, making it a condition every dog owner should understand.
There are four main types of allergies in dogs: environmental (atopic dermatitis), food allergy, flea allergy dermatitis (FAD), and contact allergy. FAD is the most common dermatologic disease of dogs according to the Merck Veterinary Manual, followed by environmental allergies, then food allergies. Contact allergies are rare. Importantly, dogs can have multiple allergy types simultaneously — food-allergic dogs frequently have concurrent environmental or flea allergies.
Symptoms by Allergy Type
Environmental allergies (atopic dermatitis)
Environmental atopic dermatitis is caused by an immune overreaction to inhaled or contact allergens like pollen, dust mites, and mold spores. Itching is typically focused on the face, paws, belly, ears, and armpits. Onset is most common between 1–3 years of age (a Favrot diagnostic criterion). Symptoms are often seasonal when caused by pollens but can be year-round with dust mite or mold allergies. Recurrent ear infections (otitis) are very common. Affected dogs typically respond to corticosteroid treatment, which is another Favrot criterion.
Food allergies
Food allergy in dogs is clinically indistinguishable from atopic dermatitis based on symptoms alone, as confirmed by Favrot et al. (2010). Key differentiating clues include: non-seasonal, year-round symptoms; gastrointestinal signs (vomiting, diarrhea, excessive gas) present in 30–50% of cases; onset at less than 1 year or greater than 7 years of age; and failure to respond to corticosteroid treatment in approximately 50% of cases. The only reliable diagnosis is an 8–12 week strict elimination diet trial using a novel protein or hydrolyzed diet, followed by a rechallenge to confirm.
Flea allergy dermatitis (FAD)
FAD is a hypersensitivity reaction to proteins in flea saliva and is the most common dermatologic disease of dogs. The characteristic distribution pattern is caudodorsal — the lower back, tail base, rear legs, and belly, often called the “flea triangle.” A single flea bite is sufficient to trigger the reaction in sensitized dogs; a full infestation is not required. FAD is often seasonal in temperate climates but year-round in warmer regions. Starting all pets in the household on year-round flea prevention is both the treatment and the diagnostic test.
Contact allergy
Contact allergies are rare in dogs due to the protective haircoat, with few well-documented cases in the veterinary literature according to the Merck Veterinary Manual. They affect sparsely-haired areas that come into direct contact with irritants — the belly, groin, between the toes, and areas under collars. Triggers include cleaning products, lawn chemicals, carpet fibers, and flea collars. Contact allergy requires repeated exposure over 6 months to 2 years for sensitization to develop.
Breed Predispositions to Allergies
Research spanning five locations across three continents (Jaeger et al. 2010) has identified breeds consistently predisposed to atopic dermatitis worldwide: Boxer, Bulldog, Labrador Retriever, Pug, and West Highland White Terrier. The WHWT has a particularly high predisposition, with a Swiss cohort study finding a 52% lifetime prevalence of canine atopic dermatitis. Additional breeds documented as overrepresented include French Bulldog, Golden Retriever, German Shepherd, Cocker Spaniel, Dalmatian, Shar-Pei, and Irish Setter. For food allergy specifically, German Shepherds, Labrador Retrievers, and French Bulldogs are overrepresented according to JAVMA (2023).
How Veterinarians Diagnose Allergies
Canine atopic dermatitis is a diagnosis of exclusion, following the ICADA (International Committee on Allergic Diseases of Animals) guidelines outlined in Hensel et al. (2015). The diagnostic process follows a systematic approach:
- Rule out parasites — Skin scraping, coat combings, and trial antiparasitic treatment to exclude sarcoptic mange, demodex, and fleas.
- Rule out infections — Cytology to identify secondary bacterial or yeast infections that may mimic or complicate allergies.
- Elimination diet trial — A strict 8–12 week trial using a novel protein or hydrolyzed diet to rule out food allergy. This is the only validated method for diagnosing food allergy in dogs.
- Allergy testing — If all of the above are excluded, intradermal skin testing (IDAT) is the gold standard for identifying specific environmental allergens, as endorsed by the American College of Veterinary Dermatology (ACVD).
It is important to note that blood-based allergy tests (serum IgE tests) are not considered reliable for diagnosis by most veterinary dermatologists. At-home saliva and hair allergy tests are not validated by any veterinary organization and should not be used to guide treatment decisions.
When to See the Vet for Allergy Symptoms
If you suspect your dog has allergies, always consult with your veterinarian. Allergies in dogs are complex, often overlapping conditions that require professional evaluation for proper diagnosis and treatment. Your vet can help identify whether your dog is dealing with environmental allergies, food sensitivities, flea allergy dermatitis, or a combination of these. Common signs that should prompt a vet visit include: recurrent ear infections, significant hair loss or skin thickening, persistent itching or scratching, digestive symptoms alongside skin issues, open sores or hot spots, and symptoms that are worsening over time. Food allergies in particular require veterinary supervision, as elimination diets must be conducted properly to yield accurate results.
Seek emergency care immediately if your dog shows signs of anaphylaxis: sudden facial or throat swelling, difficulty breathing, collapse, pale or blue gums, or hives with vomiting. Canine anaphylaxis typically occurs within 30 minutes of allergen exposure and can be life-threatening. The primary target organs in dogs are the gastrointestinal tract and liver (unlike lungs in humans), so severe GI signs with collapse are hallmark presentations. With prompt treatment, the survival rate is approximately 85%.
Sources & references
- Favrot et al. (2010) — “A prospective study on the clinical features of chronic canine atopic dermatitis and its diagnosis.” Veterinary Dermatology 21(1):23–31. Provides Favrot’s 8 criteria (77% sensitivity, 83% specificity) for canine atopic dermatitis diagnosis.
- Hensel, Santoro, Favrot et al. (2015) — “Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification.” BMC Veterinary Research 11:196. ICADA diagnostic algorithm and differential diagnosis framework.
- Jaeger et al. (2010) — “Breed and site predispositions of dogs with atopic dermatitis: a comparison of five locations in three continents.” Veterinary Dermatology 21(1):67–75. Multi-continent breed predisposition data.
- Hensel et al. (2024) — “Update on the role of genetic factors, environmental factors and allergens in canine atopic dermatitis.” Veterinary Dermatology. Updated breed predisposition and genetic basis review.
- JAVMA (2023) — “Food allergy in dogs and cats; current perspectives on etiology, diagnosis, and management.” J Am Vet Med Assoc 261(S1). Food allergy prevalence, GI sign frequency, steroid non-response rate, elimination diet protocol.
- Merck Veterinary Manual — Flea Allergy Dermatitis, Canine Atopic Dermatitis, Contact Dermatitis. FAD body distribution patterns, prevalence data, contact allergy rarity.
- Cornell University College of Veterinary Medicine — Atopic Dermatitis (Atopy). Prevalence estimate: 10–15% of the dog population.
- Anturaniemi et al. (2017) — “Environmental and phenotype-related risk factors for owner-reported allergic/atopic skin symptoms.” PLOS ONE. Finnish breed predisposition data and environmental risk factors.
- Gustafsson et al. (2022) — “Bayesian model and selection signature analyses reveal risk factors for canine atopic dermatitis.” Communications Biology. Genetic basis with 15 associated loci.
- Today’s Veterinary Practice — “Anaphylactic Shock: How to Effectively Diagnose and Treat.” Emergency triage criteria, canine anaphylaxis presentation, 85% survival rate data.
- American Animal Hospital Association (AAHA) — General canine health guidelines.
- ASPCA — Dog allergy resources and emergency guidance.
Disclaimer: This tool identifies likely allergy types based on symptom patterns and evidence-based veterinary literature. It is not a substitute for professional veterinary examination and diagnosis. Canine atopic dermatitis is a diagnosis of exclusion that requires clinical testing. Always consult your veterinarian for personalized medical advice. In case of emergency symptoms (facial swelling, difficulty breathing, collapse), seek immediate veterinary care.
Frequently asked questions about dog allergies
What are the most common signs of allergies in dogs?
The most common allergy signs in dogs include itching and scratching (especially around the face, paws, belly, and ears), recurrent ear infections, paw licking or chewing, skin redness or rash, hair loss, hot spots, and digestive issues like vomiting or diarrhea. Skin-related symptoms are the most frequent presentation, with itching (pruritus) being the hallmark sign of canine allergic disease.
How can I tell if my dog has food allergies or environmental allergies?
Unfortunately, food allergies and environmental allergies (atopic dermatitis) in dogs are clinically very similar and cannot be reliably distinguished by symptoms alone, as confirmed by Favrot et al. (2010). However, some patterns can suggest one over the other: year-round symptoms with digestive involvement lean toward food allergy, while seasonal symptoms that worsen in spring/summer lean toward environmental allergy. The only definitive way to diagnose food allergy is a strict 8–12 week elimination diet trial supervised by your veterinarian.
What does flea allergy dermatitis look like in dogs?
Flea allergy dermatitis (FAD) typically causes intense itching concentrated on the lower back, tail base, and rear legs — a pattern veterinarians call the "flea triangle" or caudodorsal distribution. Affected dogs often develop hair loss, hot spots, and thickened skin in these areas. Importantly, a single flea bite can trigger the reaction in sensitized dogs — you do not need to see fleas or find an infestation for FAD to be the cause.
Which dog breeds are most prone to allergies?
Research spanning multiple continents (Jaeger et al. 2010) has identified several breeds consistently predisposed to atopic dermatitis: West Highland White Terrier (52% lifetime prevalence), Boxer, Bulldog, Labrador Retriever, and Pug. Additional breeds overrepresented in allergy studies include French Bulldog, Golden Retriever, German Shepherd, Cocker Spaniel, Shar-Pei, and Dalmatian. For food allergies specifically, German Shepherds, Labrador Retrievers, and French Bulldogs are overrepresented.
When should I take my dog to the vet for allergy symptoms?
You should always consult with your veterinarian if you suspect your dog has allergies. Common signs that warrant a vet visit include: recurrent ear infections, significant hair loss or skin changes, persistent itching or scratching, digestive symptoms (vomiting, diarrhea) alongside skin issues, open sores or hot spots, and symptoms that are worsening over time. Seek emergency care immediately if your dog shows signs of anaphylaxis — sudden facial swelling, difficulty breathing, collapse, or hives with vomiting.
How do veterinarians diagnose allergies in dogs?
Canine atopic dermatitis is a diagnosis of exclusion, following ICADA (International Committee on Allergic Diseases of Animals) guidelines. The process involves: (1) ruling out parasites via skin scrape, (2) ruling out infections via cytology, (3) a strict elimination diet trial to rule out food allergy, and (4) if all are excluded, intradermal skin testing (the gold standard per ACVD) to identify specific environmental allergens. Blood-based allergy tests are not considered reliable for diagnosis by most veterinary dermatologists.
Can dogs have multiple types of allergies at the same time?
Yes, dogs commonly have multiple allergy types simultaneously. According to JAVMA (2023), food-allergic dogs frequently have concurrent environmental or flea allergies. This comorbidity can make diagnosis more challenging, as treating one allergy type may only partially resolve symptoms. This is one reason why a systematic veterinary workup is important — addressing only one allergy type may not fully resolve your dog's symptoms.
How does this tool determine my dog’s likely allergy type?
This tool uses a weighted scoring model derived from peer-reviewed veterinary literature, including Favrot et al. (2010), Jaeger et al. (2010), JAVMA (2023), and the Merck Veterinary Manual. Each symptom, body location, timing pattern, and contextual factor contributes weighted points to four allergy categories (environmental, food, flea, contact). Breed predispositions apply multipliers based on documented genetic susceptibility. The final assessment ranks categories by score, but it is not a diagnosis — only your veterinarian can diagnose allergies through proper clinical testing.