Allergies explained: A deep dive into what can cause allergic reactions and what allergies look like
Allergies aren’t just a “pet thing”, they’re a very common issue for both dogs and cats, and they can show up in so many different ways that pet parents sometimes don’t even realize what's going on. One minute your pet is living their best life, and the next they’re scratching nonstop, sneezing like crazy, or dealing with mysterious skin issues.
Let’s break down what allergies actually are, what causes them, and what allergy symptoms look like in both dogs and cats.
What Exactly Are Allergies?
Allergies happen when your pet’s immune system overreacts to something that should be harmless — like pollen, dust, or a certain protein in their food.
Their body treats it like an intruder and kicks off a whole response that leads to itching, redness, ear issues, or digestive trouble.
Allergies aren’t curable, but they are manageable once you understand what’s triggering them.
Common Causes of Allergies in Dogs and Cats
Even though cats and dogs are different species, the main categories of allergens are the same.
1. Environmental Allergies (Atopy)
These come from things in their surroundings:
Pollen from trees, weeds, grasses
Mold
Dust mites
Cleaning products
Fabrics or carpet fibers
Fragrances or scented products
Cats are especially sensitive to indoor triggers, since they usually spend more time inside.
2. Food Allergies
Food allergies usually stem from proteins, not grains.
Common triggers for dogs:
Chicken
Beef
Dairy
Eggs
Lamb
Fish (for some)
Soy
Common triggers for cats:
Chicken
Fish
Beef
Dairy
Eggs
Cats can develop allergies later in life, even if they’ve been eating the same food for years.
3. Flea Allergy Dermatitis
This affects cats and dogs. Pets who are allergic to flea saliva can react intensely to even one flea bite.
Cats tend to over-groom when they’re itchy, so sometimes you don’t see them scratching, you just notice thinning fur or bald spots.
4. Contact Allergies
This is less common but still possible in both species.
Examples include:
Certain shampoos
Cleaning sprays
Rubber or plastic materials
Lawn treatments
These reactions usually show up on the paws, belly, or chin (especially for cats).
What Allergy Symptoms Look Like in Dogs and Cats
Skin & Coat Symptoms
Shared signs both dogs and cats may show:
Constant scratching or licking
Red, irritated skin
Flaky or dry patches
Hot spots
Hair loss or thinning
Discoloration on paws from licking
Bumps, rashes, or scabs
Dog tendencies:
Dogs often chew their paws, rub their face on the floor, or scratch their sides.
Cat tendencies:
Cats might hide more, over-groom (leading to bald patches), or develop lesions known as “miliary dermatitis” — tiny bumps that feel like crusty scabs along the back or neck.
Ear Problems
Allergies love to show up as ear issues — in both species.
Red, irritated ear canals
Frequent head shaking
Wax buildup
Odor
Repeated ear infections
Cats, in particular, may scratch around their face or neck due to ear discomfort.
Digestive Symptoms
More common with food allergies.
Signs include:
Soft stool or diarrhea
Vomiting
Gas
Frequent hairballs (cats)
Reduced appetite
Cats are more subtle, so little changes — like eating less or vomiting “just once a week” — can easily be overlooked.
Respiratory Symptoms
These show up more in cats than dogs.
Cats may experience:
Wheezing
Chronic coughing
Sniffling or sneezing
Watery eyes
Nasal discharge
Sometimes cats with allergies are mistaken for having a “cold.”
Dogs may show:
Sneezing
Runny eyes
Occasional coughing
How Groomers Spot Allergy Issues
As groomers, we often catch early signs because we’re hands-on with your pet’s skin and coat.
Things we look for during both cat and dog grooming:
Redness in the armpits, groin, paws, or belly
Dry or flaky skin
Unusual odors from the skin or ears
Hair loss patterns
Excessive shedding
Over-groomed areas in cats
Reactions to certain shampoos or products
Groomers can’t diagnose allergies, but we can definitely notice red flags and give you a heads-up.
When You Should Talk to Your Vet
You’ll want to bring your vet into the conversation if your pet has:
Chronic itching
Repeated ear infections
Bald spots or over-grooming (cats)
Ongoing skin infections
Vomiting + skin issues
Seasonal flare-ups
Flea sensitivity
Vets can help pinpoint the cause through testing, elimination diets, and treatment plans.
How to Help a Pet With Allergies
Every pet is different, but these things often help:
Regular grooming to remove allergens from the coat
Hypoallergenic shampoos and conditioners
Omega-3 supplements (get our Pet Health Multivitamins!)
Using unscented household products
Wiping paws after walks
Air purifiers for indoor cats
Consistent flea prevention
Switching to a limited-ingredient diet
Vacuuming fabrics and carpets often
Bedding made from natural materials
Cats especially benefit from environmental clean-up, because they spend most of their time inside.
Final Thoughts
Allergies can look like a hundred different things, and they can easily be mistaken for behavior issues, skin problems, or “just shedding.” But once you understand the triggers and the signs, it becomes so much easier to help your pet feel comfortable again.
Whether you have a dog, a cat, or both, consistent grooming, a clean environment, and the right care plan make a huge difference.
If you're ever unsure about what's going on with your pet’s skin, coat, or behavior, Ask Ciara, our owner/pet professional or talk to your local vet/groomer. We’re always here to point you in the right direction and help you keep your furry family member feeling good year-round.
