The short answer
Seasonal allergies follow the pollen calendar and mostly affect the skin. Food allergies cause year-round symptoms and are more likely to involve digestive issues alongside the itching. Only about 0.2% of dogs in the general population have true food allergies, while an estimated 10 to 15% deal with seasonal allergies.
Seasonal (environmental) allergies
These are triggered by things your dog inhales or contacts outdoors: tree pollen, grass pollen, ragweed, mould spores, and dust mites. In Ontario, symptoms typically flare from April through October and follow a predictable annual pattern.
The itching targets specific areas: paws, belly, armpits, ears, and face. Paw licking is often the first sign. Chronic ear infections that come back every spring or summer are another hallmark.
Environmental allergies usually appear between ages 1 and 3. They rarely start in puppies under 6 months or in senior dogs who’ve never had them before.
Food allergies
True food allergies are far less common than most people think. That 0.2% figure comes from large-scale veterinary data. The most common culprits are proteins: beef, dairy, chicken, wheat, and soy.
The biggest clue is year-round symptoms with no seasonal variation. If your dog is just as itchy in January as in July, food deserves a closer look. The other telltale is gastrointestinal symptoms alongside the skin issues: soft stool, vomiting, excessive gas, or frequent bowel movements. Seasonal allergies rarely cause gut problems.
Food allergies can also target the skin around the eyes and the ears more heavily than seasonal allergies do.
The overlap problem
About 30% of dogs with food allergies also have environmental allergies. That’s what makes this so hard to sort out at home. A dog with both will itch all year but get worse during pollen season. Without a systematic approach, it’s easy to miss one of the two.
How your vet figures it out
There’s no reliable blood test for food allergies in dogs. The gold standard is an elimination diet trial: feeding a novel protein or hydrolyzed protein diet for 8 to 12 weeks and watching for improvement. If symptoms clear up and return when the old diet is reintroduced, you have your answer.
Environmental allergies can be diagnosed through intradermal skin testing or blood-based allergen panels. We cover the costs and details of allergy testing here.
Don’t try to shortcut the elimination trial by just switching to a grain-free food. Grain allergies in dogs are rare. The problem is almost always a protein, and many “grain-free” diets still contain the same proteins.
Key takeaways
- Seasonal allergies are common (an estimated 10 to 15% of dogs) and follow Ontario’s pollen calendar. Food allergies are rare (about 0.2% of the general dog population) and cause year-round symptoms.
- Gut symptoms (vomiting, soft stool, gas) alongside skin issues point toward food allergies.
- About 30% of food-allergic dogs also have environmental allergies. Sorting them out takes a systematic approach.
- The only reliable food allergy test is an 8 to 12 week elimination diet. Blood tests for food allergies are not accurate.
- Grain-free diets don’t solve protein allergies. Talk to your vet before changing foods.
References
- PetMD. “Food Allergies vs. Seasonal Allergies in Dogs.” petmd.com
- Small Door Veterinary. “The Difference Between Food Allergies and Environmental Allergies in Dogs.” smalldoorvet.com
- PetMD. “Food Allergies and Intolerances in Dogs.” petmd.com
- Olivry, T. et al. “Canine Atopic Dermatitis: Prevalence, Impact, and Management Strategies.” Veterinary Medicine: Research and Reports, 2024. pmc.ncbi.nlm.nih.gov