What Are Cats Allergic To? Common Allergens 

When you hear the phrase “cat allergies,” your mind probably goes to humans who are allergic to cats. That’s not surprising, as an estimated 10 to 20 percent of people are allergic to our feline friends (1). But humans aren’t the only ones who suffer from allergies—cats can also be allergic to many of the same things as people. 

Luckily, cats are not typically allergic to humans, but we do share some common allergens. Cats can be allergic to environmental allergens like dust and pollen, certain types of food, and flea saliva. But how can you tell if your cat has an allergy, and how do you pinpoint what is causing the reaction? Here’s what you need to know.

Signs of Allergies in Cats

The most common signs of environmental and flea allergies in cats are seen in the skin and ears. “Skin and ears can become itchy. There could also be fur loss,” explains Emily Swiniarski, DVM, chief medical officer of PAWS Chicago in Chicago, Illinois. “However, cats are very secretive, so you might not see them scratching.”

Cats with allergies often get secondary skin infections or have red bumps, especially if fleas are involved. Cats can also get a rash-like skin condition called miliary dermatitis in response to allergens.

In addition to thinning fur behind the ears, allergy cats can have inflammation and hair loss on the face, neck, lower back/rump, belly, and thighs.

With food allergies in cats, the most common sign is itchy, irritated skin. That being said, there is the possibility that a food allergy could also cause gastrointestinal symptoms, such as diarrhea, vomiting, change in appetite, and weight loss.

It can be very difficult to diagnose allergies in cats. “Sometimes we joke that cats don’t read our textbooks, because there can be a wide variety of clinical presentations for different ailments, including allergies,” says Dr. Ekaterina Mendoza-Kuznetsova, V.V.Z., DECVD, assistant clinical professor in the Department of Clinical Sciences at Tufts University Cummings School of Veterinary Medicine in North Grafton, Massachusetts. “On top of that, it can also be difficult to differentiate allergies from similar conditions.”

What Are Cats Allergic To? Common Allergens

As mentioned earlier, cats and people can be allergic to many of the same things. “Anything that could create allergies in a human can create allergies in a cat,” Dr. Swiniarski says. “They can be allergic to all sorts of grasses, pollen, and plants, as well as dust mites, fleas, and dogs or other pets.”

Allergies in cats can be broken down into a few general categories, including:

• Flea allergies (flea allergy dermatitis, caused by flea bites)
• Environmental allergies (e.g., pollen, grass, dust, mold)
• Food allergies
• Contact allergies (anything that comes in contact with the skin, such as shampoos, or fabrics like wool)
• Feline asthma (triggered by inhaled substances in the air like smoke or perfume)

Perhaps the most common allergen for cats is flea bites. “With a flea allergy, a single bite can cause a hypersensitive reaction that could potentially last for a couple of weeks,” Dr. Mendoza-Kuznetsova says. “And you might never see a flea. All it takes is one bite and for the flea to jump to a different host.”

What Plants Are Cats Allergic To?

In addition to common environmental allergens like dust and mold, pollen spread by plants can cause allergies in cats. Common culprits include tree pollens, grass pollens, weed pollens, and flower pollens.

If your cat is showing signs of an environmental allergy, your veterinarian may treat them without knowing exactly which allergen is to blame. “Cats can be allergic to a variety of grasses, trees, shrubs, and flowers, but it’s hard to figure out which one is causing the reaction,” Dr. Swiniarski says. There is also a lack of scientific research into which plants cats might be most allergic to. This may have to do with how difficult it is to diagnose allergies in cats.

What Foods are Cats Allergic To?

When it comes to food allergies, cats are most often allergic to proteins, such as meat and dairy. Common food allergens in cats include:

• Chicken
• Beef
• Turkey
• Egg
• Soy
• Milk

Food allergies can present suddenly, even if a cat has been eating the same food for years, Dr. Mendoza-Kuznetsova notes. “A cat may have been eating chicken for a decade without any problems. But suddenly—and no one knows why—this cat may develop an allergy to chicken. Onset is unpredictable.” 

Cats cannot be allergic to a food that they have never tried before, Dr. Mendoza-Kuznetsova adds. So, if a cat presents with a chicken allergy, a common solution is to transition that cat’s diet to a novel protein, such as lamb. 

How to Help Your Cat with Allergies

If your veterinarian determines that your cat is suffering from allergies, there are some steps you can take to help your feline companion.

For cats with flea bite allergies, the most important step is to get them on a good flea control product. “It may take a few months, but a flea control product will decrease the number of fleas around a cat, which will lead to less bites,” Dr. Mendoza-Kuznetsova says.

If your cat has a food allergy, an elimination diet is necessary to pinpoint the food that is causing the issue. “The only way to diagnose a food allergy is a diet trial, which is very strict and not easy for picky eaters like cats,” Dr. Mendoza-Kuznetsova explains. You will work with your veterinarian to systematically remove different foods from your cat’s diet until there is an improvement in symptoms. To confirm that a particular ingredient is the culprit, you add it back to the diet and see if clinical signs reappear. Any offending foods are then permanently removed from your cat’s diet. 

As for environmental allergies, there are intradermal skin tests available, but they are not generally used to make diagnoses. “They’re only used for identifying what a cat is likely allergic to once we determine that cat is suffering from an environmental allergy, and they’re only utilized after a clinical workup has been done by a veterinarian,” Dr. Mendoza-Kuznetsova says.

It’s impossible to keep your cat safe from all allergens, especially ones like pollen and dust that get into your home, no matter how clean you keep it. That means that pet parents who have cats with environmental allergies should focus on treating symptoms, rather than trying to prevent them from happening.

“Your vet may recommend an antihistamine like cetirizine—also known as Zyrtec—to help mitigate your cat’s symptoms,” Dr. Swiniarski says. “We also have medications that can help with itchiness that we prescribe relatively frequently.” Many cats with allergies usually need more than antihistamines alone—they might need cyclosporine (Atopica) or another immunomodulator. Allergy shots (allergen-specific immunotherapy/ASIT) are also used in cats to help improve their tolerance to allergens.

As with any medical issues, pet parents should work with their cat’s care team to develop a treatment plan and should not give any medication without consulting with their veterinarian first.