FAQ: What Types of Allergies Do Cats Most Commonly Have?

When you think about cat allergies, you're most likely thinking about the sniffles you, a loved one, or maybe a friend get whenever you're around a cat.

But did you know that cats can have allergies, too?

It's true. Pretty much any living thing can have allergies, but what are they, and what allergies can cats have? After all, if your fur baby is having allergic reactions, you want to do what you can to minimize them so they don't suffer.

What Are Allergies?

Let’s start off with the basics, in the truest sense of the word, allergies are symptoms resulting from an immune response.

Complex, multi-cellular living things have immune systems. The immune system is a complex set of tiny processes in the body that help protect it from outside invaders. It's purpose is to help protect you against things like viruses, bacteria, and fungal infections, things that are also alive and trying to invade and use your body as a breeding ground to grow their own colonies.

When those nasties get a foothold, you get sick. Whether it's a cold, the flu, COVID-19, a rash, or any other kind of infection, it's a case where the immune system hasn't been able to fight off the invader. Usually, the immune system is hard at work fighting it off, and once it learns how, you'll recover from the illness. Sometimes, you need assistance from antibiotics or other medications.

What happens when the immune system identifies something as an invader when it's really harmless, though?

For example, dust mites, pet dander, grass pollen, and even things like bee sting venom and peanuts can all trigger an immune response.

"Allergens are foreign proteins that the body's immune system tries to remove. Examples of allergens common in humans are pollens, dust, molds, and pet hair." - VCA.

That's right; it's an allergy. An allergy is simply the body trying to use the immune system to fight off something that isn't really a danger and isn’t fightable in the traditional immune sense. So, you may get some of the symptoms of getting sick without the "getting sick" part.

The term allergy is often used interchangeably with the word sensitivity, but they aren’t actually one and the same. While they both may produce the same symptoms (we’ll get into these in a bit), a sensitivity does not involve an immune response. Sensitivities are an irritant and usually have more mild symptoms and are not life threatening.

Are Allergies Common in Cats?

Actually, yes! Allergies are one of the most common medical conditions to affect cats.

Sure, cats can get sick, get cancer, and have all sorts of terrible things happen to them, but allergies are simply so common, with so many different possible things they can be exposed to that can trigger them.

Allergies can present in a few different ways, and there are four main groups of allergies that can affect cats.

What do Allergies in Cats Look Like?

Generally, allergies will show up in one of three ways. Different kinds of allergies can express differently, so you can get some idea of what kind of allergy your cat is suffering from based on what kind of symptoms they're having.

The three kinds of allergic reactions are:

• Dermatologic. That is, skin reactions. Itchy, red patches, with swollen skin beneath, flaking skin, and occasionally something more extreme, like hives, can be a sign of an allergic reaction. This can be localized to just a small area, or it can cover large patches of the body or even be a full-body reaction for the most unfortunate feline friends of ours.
• Digestive. If your fur baby eats something that triggers a reaction in them, it can range anywhere from mild to severe. Mild reactions are mostly limited to soft stool and those nasty, room-clearing kitty farts (though those are more of a dog thing in general). Meanwhile, more severe reactions can include diarrhea and vomiting. If left untreated, it can also lead to secondary problems like dehydration and malnutrition.
• Respiratory. All of those irritating symptoms we get when we have seasonal allergies are the same sorts of things cats can get. Sniffles, sneezing, congestion, coughing, wheezing, runny nose, and itchy and watery eyes are all common symptoms of common allergies. In the case of something more severe, the windpipe can swell up and make breathing difficult or even impossible; that's when you need to bring your fur baby in for immediate medical treatment.

Usually, but not always, symptoms are going to be limited to one of these three groups. Sometimes, they can overlap a bit, though; for example, an insect bite allergy can cause skin reactions, but a bad enough reaction can also lead to respiratory distress. That's kind of how bee sting allergies work in people; the site of the sting is a reaction, but so too is respiratory distress and shock.

What Are the Four Types of Allergies in Cats?

While some vets may break the types of allergies into more refined groups, we’re going to stick with four main categories.

There can be some overlap between them in terms of symptoms, and severity varies wildly between different individual cats (and even throughout a cat's life), but they can broadly be broken down into these four groups:

• Flea allergies. Not your typical flea bite, but an overreaction to a bite.
• Food allergies. These are allergies related to something your fur baby is eating, perhaps only one ingredient in their food.
• Atopic Dermatitis. This is a skin reaction to environmental allergens, like dust mites. It's fairly common and one of the more complex kinds of allergies to deal with.
• Contact allergies. These are fairly similar to atopic dermatitis, though the symptoms are typically more mild and the treatment options are different.

Let's break them down individually!

What Do I Need to Know About Flea Allergies?

Flea bites are almost always very minor. Think of it like a mosquito for you; when one bites you, you get an annoying little welt that itches, but goes away on its own in a day or two, and that's pretty much it. Flea bites are the same way for most cats: itchy and irritating, but minor and will go away on their own even without treatment, that is, as long as the fleas themselves don't stick around.

As a side note, this is why you should always make sure your fur baby is up to date with their flea medications. Flea meds alter your kitty's body chemistry to make it inhospitable for fleas to live, so while they can still show up and bite, they won't linger. You can read a lot more about it here in my guide to cat flea medications.

Flea allergies are worse. When a flea bites, it injects a bit of saliva to feed without disturbance. This itches, but in a cat with flea allergies, one bite can cause a significant response.

“All cats can be affected to some extent by flea bites, but an allergic cat will react with disproportionate severity. Where it would take dozens of flea bites to significantly harm a normal cat’s skin, the same amount of damage to the skin of an allergic will result from just a few bites.” - William Miller Jr., Cornell University’s College of Veterinary Medicine

Symptoms of flea allergies include:

• Skin bumps (known as miliary dermatitis)
• Itching
• Scratching
• Chewing of the skin
• Sores and scabs
• Presence of fleas, flea eggs, or flea dirt
• Secondary infections

What Do I Need to Know About Food Allergies in Cats?

Remember earlier when we talked about the difference between an allergy and a sensitivity? Food allergies are the perfect place to dig into this difference in more detail.

There are differing positions on the prevalence of food allergies in cats.

Cornell Feline Health Center, among others argue food allergies are the “thirst most common type of feline allergy.”

However, a study released in 2018, conducted by Banfield Animal Hospital looked at 2.5 million dogs and 500,000 cats and it showed food allergies in cats and dogs aren’t quite as prevalent as many people think.

“Food allergies affect just 0.2 percent of dogs and 0.1 percent of cats” – American Veterinary Medical Association

While earlier than the Banfield study, a prior study in 2006 ‘Food allergy in dogs and cats: a review’ found:

“The exact prevalence of FA [food allergies] in dogs and cats remains unknown.”

Seems like the jury is still out on this one.

The gap between these perspectives may be related to the grouping of food allergies, sensitivities, and intolerances, with the basic difference being the immune system is involved in one, but not the others.

For the sake of this post, we’re going to group all three issues together as many of the symptoms overlap, and ultimately have a similar resolution, though getting there will vary.

Food allergies are particularly tricky because it's hard to tell what your fur baby is allergic to in the first place. Tracking down what, specifically, is causing the allergic reaction is very important so you can avoid it in the future.

Some of the most common cat food allergies are related to the protein in their diet and include beef, chicken, and fish. Bear in mind any ingredient could potentially be a trigger, preservatives, gums, grains, etc.

Symptoms of Food Allergies and Intolerances

Severity of symptoms can vary, and may include some or all of the following:

• Red skin
• Fluid filled bumps on the skin (often on the head and neck)
• Itching
• Scratching
• Flakey skin
• Loss of hair
• Vomiting
• Diarrhea
• Frequent visits to the litter box
• Gas
• Weight loss

If your vet suspects a food allergy is at play, they may recommend an "elimination diet," where you restrict what your fur baby can.

Elimination diets are tricky:

"Testing is conducted by feeding an elimination or hypoallergenic diet. This means a diet in which the ingredients have not previously been fed to the cat (e.g., duck, rabbit, venison). Because it takes at least eight weeks for all other food products to be removed from the body, the cat must eat the special diet exclusively for a minimum of eight to twelve weeks.

Unless the diet is fed exclusively, the test is meaningless. This means absolutely no treats, other foods, people foods, or even flavored medications during this trial. This cannot be overemphasized. Even accidentally providing a tiny amount of the offending protein can invalidate the test." – VCA.

If symptoms resolve on the hypoallergic diet, a food allergy is likely the case. To confirm, your vet may ask you to reintroduce their old food to see if symptoms return.

What Do I Need to Know About Atopic Dermatitis in Cats?

Atopic dermatitis is a skin irritation caused by something in the environment.

Often, these allergies are seasonal because they're related either to the life cycle of something like a dust mite or, more often, to the pollen of a plant that only flowers during specific times of the year.

Symptoms of atopic dermatitis are generally limited to the skin and can include:

• Redness of the skin
• Itching
• Scratching
• Scabs
• Excessive Licking
• Fur Loss
• Ear Infections

There are two types of allergy tests that can be done on your cat, intradermal allergy testing (IDAT) and radioallergosorbent testing (RAST).

The RAST test is pretty straight forward, a blood sample is taken by your vet and sent to a lab for review. While affordable, it’s not very reliable, though it could be a starting point for diagnosis.

A more accurate test is the IDAT, where small amounts of potential allergens are injected and then observed for a response. This test is more expensive and may require a visit to a specialist.

There is also serologic testing (RAST), which is done with your cat’s blood. This testing tends to be less reliable, but it could be a starting point for diagnosis.

A 2019 study has shown hair and saliva tests are not accurate allergen tests.

What Do I Need to Know About Contact Allergies in Cats?

Contact allergies are the least common allergy in cats and are a kind of dermatitis that isn't atopic; that is, it has a defined, specific cause. It can be a reaction to a shampoo, or to a flea collar, or to natural fibers like wool. It can also be something natural like poison ivy.

Symptoms of a contact allergy will be seen just at the location of “contact” and include:

• Redness
• Itching
• Bumps

These symptoms are generally minor, and will resolve once the source of the reaction is removed.

Cats can also be sensitive to plastic. That “dirt” on your cat’s chin is not actually dirt, but feline acne. Plastic is very porous and a great breeding ground for bacteria.

If your cat has little back specs on their chin, the first thing you should do is swap out any plastic bowls for stainless steel, glass, or ceramic.

What Do I Need to Know About Asthma in Cats?

A post about cat allergies deserves a section on feline asthma. While it’s estimated only 1% of cats living in the US suffer from asthma, it is believed to be triggered by an allergen.

Asthma is when the airways to the lungs become narrowed due to inflammation, making it harder for your cat to breathe.

Symptoms of asthma include:

• Open mouth breathing
• Wheezing or coughing
• Increased respiratory rate

Asthma attacks can range from mild to severe, and it is incurable.

Diagnosing asthma can take several tests to rule out other causes of labored breathing. Your vet will start with a physical exam, followed by bloodwork, and may order an x-ray to get a better look at your cats lungs.

What Can I Give My Cat for Allergies?

The first challenge is identifying the cause of the allergy, but some common treatment options include OTC antihistamines, an oatmeal bath, fish oil supplement, corticosteroids, and topical prescription medications.

Flea Allergies

If your cat has a flea allergy, monthly preventative treatments are a must, even if they are indoor only.

You’ll also want to ensure you’ve thoroughly cleaned your home if fleas have been present.

If your kitty is currently suffering from an acute severe reaction to flea bites, talk to your vet about medications that may be helpful.

Food Allergies

A strict diet is the only solution for a cat with food allergies. This may include feeding a prescription diet or switching to a different brand of food that doesn’t include any ingredients your cat is allergic to.

If you have multiple cats in your household and feed them different foods, it’s important to ensure your allergic kitty isn’t sampling any of the other food or symptoms are likely to return.

You’ll also need to be aware of reactions after treats or supplements. Symptoms may not appear immediately, so it can be difficult to identify the new offender, so make a note if you offer any special treats so you’ll remember down the line if symptoms show up.

If your kitty got into something they shouldn’t and has an acute bout of symptoms, talk to your vet about medications to get them over the hump, this may include something to stop vomiting or diarrhea, and/or an antihistamine for skin reactions.

Atopic Dermatitis

If your cat is allergies to environmental allergens, keeping them indoors can reduce their exposure. Doing more regular cleaning can help with indoor allergens.

You may also consider giving your kitty a fish oil supplement. The omega-3 fatty acids in the oil are anti-inflammatory and can help with skin allergies.

Because some cats with atopic dermatitis may also have a food allergen, your vet may recommend a hypoallergenic diet.

There are also a few medical options to help with atopic dermatitis and your vet will help you decide what’s best for your cat.

Your vet may start with prednisolone, which is generally well tolerated and provides quick results. Antihistamines may also be an option.

For more severe cases immunotherapy may be recommended. This treatment is regular injections or sublingual drops. Yep, just like humans with several allergies, cats can get allergy shots too! This treatment can take months to work, so supportive therapy for symptoms may also be needed.

There are also immune-modulating medications that suppress the overreaction of the immune system. These medications can make your cat more susceptible to infections and there are potential side effects, so you’ll have to weigh the benefits and risks.

Contact Allergies

Addressing contact allergies is fairly simple, remove access to the things your cat is allergic to. The challenge is first identifying the offending substance.

To help identify the allergen, look for the areas of the body that are showing an allergic reaction. Is it just around the neck? Do they wear a flea collar, easy fix. If you suspect bedding or toys might be the offender, remove to determine if the symptoms resolve.

When it comes to cleaning products, switch to pet safe brands and always remove your fur baby from the area while cleaning is taking place.

Asthma

The treatment of choice is usually an inhaled corticosteroid, just like you’ve seen used in humans, though the device doesn’t go in the mouth, but over your kitty’s face.

If your cat suffers acute bouts of asthma, try to identify the trigger. Could it be a perfume you only use occasionally? An air freshener? Perhaps a plug in or scented litter? If you’re able to identify an allergen, you can potentially reduce the frequency of attacks.

How Dangerous are Allergies in Cats?

Most of the time, allergies range from mild to moderate in severity for cats. Generalized itching is irritating and can stress your fur baby out, but it's not life-threatening unless they scratch holes in themselves and get an infection.

In rare instances, allergies can be more severe. Whenever they cause bleeding, ulcers, sores, or infections, and any time they inhibit breathing, you should bring your fur baby to the vet.

Luckily, allergies in cats are relatively well understood, and the treatments, particularly emergency treatments, are readily available. Once they pull through, you can figure out what they were allergic to and how to get rid of it from your environment for a safe, happy kitty.

Does your kitty have allergies? If so, what kind of allergy do they have, how did you identify the allergen, and what do you do to help them manage it? I'd love to hear all your stories about your fur babies, so be sure to leave those in the comments section down below!