Feline Allergies: Part 1 - Signs and Symptoms
If you’ve ever found your cat obsessively licking, scratching, or losing fur in patches, you may have wondered: Is my cat allergic to something? As a veterinary dermatologist, I see allergic cats every day, and helping them find relief is one of my favorite parts of my job. In this post, we’ll dive into feline allergies, the most common skin reaction patterns, and how you and your veterinarian can work together to get your cat feeling comfortable again. See the full transcript following the blog post with additional images.
Meet Otto: The Bald Cat Who Got His Pants Back
One of my favorite patients, Otto, came to me completely bald on his back legs and belly. His family veterinarian had already ruled out other possible causes by making sure he was on excellent flea prevention and performing an elimination diet trial using a prescription hydrolyzed protein food. Despite all of this, Otto was still itchy. That meant he had environmental allergies—reactions to things like grass, tree pollen, dust mites, and even human dander!
We initially used steroids to stop Otto’s itching quickly, but because of the risks of long-term steroid use, we transitioned him to cyclosporine (Atopica). I also allergy-tested Otto and formulated custom immunotherapy (allergy shots) to retrain his immune system. Once his allergy shots started working, we weaned him off the medications, and Otto has been living his best life—fully clothed in fur once again!
Common Signs of Cat Allergies
When cats are allergic, they don’t usually sneeze and get watery eyes like humans. Instead, their skin reacts in one of four main ways:
1. Hair Loss from Over-Grooming (Self-Induced Alopecia)
If your cat has bald patches—especially on the belly, legs, or sides—they may be licking, chewing, or “corn cobbing” (tiny bites, like eating corn on the cob) because of intense itchiness. Many owners assume this is stress-related, but studies show that most cases are actually due to allergies! If your cat is losing fur, it’s time to talk to your vet about allergies as a potential cause.
2. Tiny Scabs and Skin Irritation (Miliary Dermatitis)
These are small, itchy scabs usually found on the head, neck, and back. They may not always be obvious until you pet your cat and feel them. If you notice scabby skin, schedule a vet visit to determine the cause and get your kitty some relief.
3. Severe Face and Neck Itching (Head and Neck Pruritus)
This is one of the most distressing reactions I see. Some allergic cats scratch their faces so aggressively that they cause bleeding, swelling, and even corneal ulcers. These cases often require urgent treatment, including medications to break the itch cycle and tools to prevent self-injury, like E-collars or nail caps.
4. Severe Plaques of Inflammation (Eosinophilic Granuloma Complex)
This is a group of three different syndromes caused by a type of immune cell called eosinophils:
- Indolent Ulcers: Sores on the upper lip that can grow larger over time.
- Linear Granulomas: Thickened, ulcerated skin, often on the backs of the thighs or even inside the mouth.
- Eosinophilic Plaques: Inflamed, raised, itchy lesions on the belly or inner thighs.
Because eosinophilic granuloma complex can look similar to infections or even cancer, your vet may recommend tests like skin cytology or biopsy to confirm the diagnosis.
How Secondary Infections Worsen Cat Allergies
When a cat’s skin is damaged from constant licking and scratching, normal bacteria and yeast that live on the skin can take advantage of the situation—causing secondary infections. If your vet sees signs of infection, they may recommend antibiotics or antifungal treatments. But remember: Treating the infection alone won’t fix the underlying allergy, so it’s important to address both issues.
How to Diagnose and Treat Cat Allergies
If you suspect your cat has allergies, the first step is to work with your veterinarian to rule out other possible causes. A good allergy workup includes:
- Ensuring excellent flea control (even indoor cats need protection!)
- Conducting a strict elimination diet trial to check for food allergies
- Evaluating for environmental allergies if symptoms persist
Once a diagnosis is made, treatment can include medications like steroids, cyclosporine, as well as long-term options like allergy immunotherapy to desensitize your cat’s immune system. Diagnosis and treatment will be discussed in upcoming episodes.
Full Transcript & more Images
Table of Contents
Case Study: Otto the Itchy Cat
Welcome, everyone, to today’s episode of Your Vet Wants You To Know. I’m Dr. Brittany Lancellotti, and I am going to be talking about some of my favorite patients- allergic cats. I absolutely love treating allergic cats at Veterinary Skin and Ear, the dermatology practice where I work in Los Angeles. I recently had a recheck with one of my favorite patients, a cat named Otto.
Otto came to me with no pants. He had licked his back legs and belly completely bald. His family veterinarian had gone through the most important steps, when figuring out what a cat is allergic to, by making sure that he didn’t have another skin disease that looked like allergies, making sure that he was on really good flea prevention (so that he wouldn’t have allergic reactions to flea bites), and doing an elimination diet trial (using a prescription hydrolyzed protein food, and no other food for eight weeks). That really great workup from his family vet allowed me to tell Otto’s owners that he was still itchy because of environmental allergies (grasses, tree pollens, weeds, dust mites, and even humans).
So we treated Otto’s symptoms with steroids to very quickly stop the itching, but because of some of Otto’s other medical history and the risks of side effects of steroids, we also started a medication called cyclosporine. The one that we put him on was Atopica, but there are a number of different forms of cyclosporine. The Atopica allowed us to eventually discontinue his steroids without the itch coming back, and helped to minimize the risks of long term steroid use. We’ll talk more about steroids and Atopica later when I go over treatment options. I also allergy tested Otto and I formulated an individual recipe for allergy specific immunotherapy (or allergy shots), to work on desensitizing Otto to the things in the environment that were triggering his allergic reactions. That’s a holistic approach to retraining the immune system.
Once the allergy shots started working, we were able to wean him off Atopica and steroids, and he has not lost his pants since. He’s a happy cat, with very dedicated owners who have worked through the steps of this often frustrating disease, and he makes my job, as a dermatologist, incredibly rewarding.
Understanding Cat Allergies
Cat allergies can be confusing and are so often misinterpreted as behavioral or anxiety problems. In the first few episodes of the podcast, I cover flea allergies, food allergies, and environmental allergies in detail. But over the next few episodes, I’m going to take a deep dive into cats, specifically.
In today’s episode, I’ll go through the most common reaction patterns that allergic cats have and how that might look on their skin. Then, I’ll talk about what your veterinarian might recommend to make sure that we’re eliminating the possibility of other problems that aren’t allergies, as well as what is commonly recommended to figure out what your cat is allergic to. Lastly, I’ll go over commonly prescribed treatments and what to consider when picking a specific plan for your individual pet.
Remember, everything I discuss on this show is evidence based. That means there is published medical data on all of the information you hear in this episode. For any veterinary professionals who may be listening, most of this data comes from the February 2021 issue of Veterinary Dermatology, which had multiple articles on feline atopic syndrome. I would highly recommend this issue if you are a veterinarian looking to help your allergic cat patients, as well as the cat course from Live Learn Vet, which is an eight hour race-approved course taught by the brilliant dermatologist, Dr. Megan Painter, that will teach you how to effectively and confidently manage allergic skin and ear disease in cats.
For pet owners looking for more help, a link to find a veterinary dermatologist near you is available on the Your Vet Wants You To Know website, under the resources tab. The other dermatology specialists at Veterinary Skin and Ear and I absolutely love caring for our Los Angeles cat community, so you can reach out to us if you’re local.
Common Allergic Reactions in Cats
1. My cat is losing hair! - Self-Induced Alopecia/Hypotrichosis
Let’s talk about some of the most common ways that allergic cats will be affected on their skin. Otto’s most common reaction pattern has a technical term called self-induced alopecia and hypotrichosis. This is a technical way of saying that the cat is pulling its hair out, either from licking, scratching, or chewing. Corn cobbing is a technique that cats will often do to cause hair loss. If you can imagine eating a corn cob and taking those little bites to get the little kernels of corn off, that’s what they’re doing on the itchy parts of their body. And instead of taking the corn kernels off, they’re taking tufts of hair.
I see a lot of bald-bellied allergic cats. That chewed and licked hair gets eaten, and the result is one of the most effective sounds for getting someone out of bed quickly in the middle of the night- the hairball. I love when pet owners tell me that their cat is having way less hairballs, once we’ve started an effective treatment. Sometimes, if they don’t barf up the hair, it may come out the other end as fuzzy poops. Some pet owners won’t see the cat licking, and they bring the cat in for hair falling out. The hair on the cat’s belly doesn’t usually just disappear. They’re often over-grooming because they’re itchy, and their tongues are like these perfect little built-in scratching tools.
Is my cat overgrooming because it is stressed?
I want to mention that stress related over-grooming is possible, but it’s often over-diagnosed when there’s actually an allergic disease. In one study of 21 cats that were referred to a behaviorist for evaluation of hair loss from anxiety, only 2 of those cats had a primary behavioral disease, 16 of the cats had hair regrowth when itch was treated, and 3 of the cats had a combination of allergies and behavioral disease. This shows just how important it is to make sure that we’re looking at allergies also, if we’re worried that there might be a behavioral problem.
2. My cat has scabs! - Miliary Dermatitis
Another common reaction pattern that we see with allergic cats is called miliary dermatitis, and these are really tiny scabs that are the result of areas of inflammation on the skin from allergies. They can be seen anywhere, but I most often find them around the head, the neck, and the back. Sometimes, these scabs are super itchy, so owners will see the cat scratch around these areas, but sometimes, these scabs can be hidden until you pet the cat and find them.
3. My cat keeps scratching its face! - Head and Neck Pruritus
The third reaction pattern that I often see, and one of the most heartbreaking, is called head and neck pruritus (intense itch that’s focused around the face and the neck). Cats with head and neck pruritus are miserable. They’re often clawing at their heads until they’re bleeding and raw, and they itch so badly that they’ll actually tear at their faces, unless they are physically restrained with things like e collars, cones, or bandages. When they’re scratching so intensely, cats can actually make their eyelids swell, or they can scratch their eyes and cause ulcers to their cornea.
One of my favorite cat patients, Tinta, had terrible head and neck pruritus when she first came to see me. She’s another cat that has done incredibly well with immunotherapy to reverse her environmental allergies, and the transformation is awesome. Cats with severe head and neck pruritus can be exceptionally challenging to treat. If you have a pet like this who is really miserable and doing a lot of damage to their face, working with a specialist should be considered, so definitely check out that website under the resources tab, to find out if there’s a dermatologist close to you.
4. My cat has an ulcer on its lip! - Eosinophilic Granuloma Complex
The fourth and last reaction pattern is called eosinophilic granuloma complex. Not only is it a mouthful, but it is a group of syndromes caused by dysfunction of eosinophils (white blood cells involved in many aspects of cat allergies). Eosinophils happen to be my favorite white blood cell because of just how beautifully pink they are under the microscope. Just a little side note, if you’re listening to this episode, and you know of any interesting eosinophil artwork out there, I would love to take a look. Just drop me a note through the ‘contact us’ page on the website. I really like these eosinophils. They’re some of my favorites.
The three syndromes that make up eosinophilic granuloma complex are:
1) indolent ulcer
2) linear granuloma and
3) eosinophilic plaque.
Indolent Ulcer (also known as Rodent Ulcer)
Indolent ulcers look like ulcers and swelling, primarily on the upper lips. When these ulcers first appear, they usually start with one side of the upper lip. The longer that this is left untreated, and the more chronic that it becomes, the larger that ulcer gets, often extending over to the other side of the upper lip, as well as up to (and potentially including) the nose. The face can become deformed and scarred if the underlying trigger isn’t found and treated appropriately.
One thing to keep in mind – there is a certain type of cancer that can occur on the face of cats called squamous cell carcinoma. So if an indolent ulcer doesn’t respond to common allergy treatments, your veterinarian may suggest a biopsy, to take a sample of the affected area, and make sure that it’s truly an indolent ulcer and not squamous cell carcinoma.
Indolent ulcers will often have secondary infection with bacteria. It’s important, when we’re treating these things, that our treatment plan includes some type of antibiotic, to make sure that the bacteria aren’t getting in the way of resolving the ulcer.
Linear Granuloma
Our second part of eosinophilic granuloma complex is a linear granuloma. These are lines of thickened skin that can become ulcerated, and they’re most often found on the backs of the thighs, which may or may not be itchy for the cat. A really great reason to decrease stress in cats, at the vet clinic, is because these thick plaques can develop, either on the tongue or the roof of the mouth, as well. It’s really hard to get a good oral exam when the cat is terrified. I try to pride myself on practicing Fear Free medicine, in the hospital, and working to reduce my patient’s stress level. But even I will admit to taking advantage of a cat hissing at me to check its mouth, to make sure that it doesn’t have an eosinophilic granuloma inside. Episodes 18 and 19 are all about how to decrease stress before vet visits, and about different medications, to give your cat a really good physical exam.
Eosinophilic Plaques
Our third part of eosinophilic granuloma complex are the eosinophilic plaques. These plaques are similar to linear granulomas. They’re both thickened areas of skin that can be ulcerated. Eosinophilic plaques can vary in shape, including circular, oval, or wavy lines. Eosinophilic plaques will most often appear on the belly or the inner thighs, but they can happen anywhere on the body. These plaques are the result of significant inflammation from allergies, and they can result in uncontrollable itch. The more the cat licks and scratches at these plaques, the worse the itch becomes, so they’re caught in this vicious itch cycle.
Cat Allergies Can Cause Swollen Paws and Ear Infections
There are also some uncommon reaction patterns, like recurrent ear infections, and swollen paws (known as plasma cell pododermatitis). Episodes 42 and 43 about ear infections are great. They guest star one of my favorite dermatologists, the lovely Dr. Megan Painter, creator of Live Learn Vet. Episode 62 is plasma cell pododermatitis, specifically, and it talks about one of my favorite cats, Hermione. Mosquito bite allergies, in cats, have a whole different look to them, so I’ll eventually cover them in a future episode.
Secondary Infections and Treatments
Secondary infections are common with many of these reaction patterns. These infections are often with the cat’s normal bacteria and yeast, which typically live in harmony on the surface of the skin. When the skin is damaged, either from inflammation from the allergies or trauma from itch caused by the allergies, the skin loses its ability to protect against normal, usually harmless germs. So those germs get into the skin, they throw a party (a bacterial bash or a yeast feast, if you will) and cause secondary infection.
Your vet may check for this with cytology, which is where a glass slide is used to collect a sample from the surface of the skin, to look at under the microscope, to see if there are bacteria or yeast or both. Your vet can then determine if they need to use antibiotics to treat bacteria, or an antifungal medication to treat yeast.
If that secondary infection isn’t treated, it can become really difficult to get some of these severe skin and mouth problems to heal. At the same time, if the secondary infection is treated, but the inflammation from the allergies (primary disease) isn’t addressed, we may get frustrated with lack of improvement or the problem quickly recurring.
If you want to learn more about cytology, episode 46 is a great episode starring Dr. Ashley Bourgeois, the Derm Vet. She talks all about how cytology can be really helpful, in figuring out what types of infection or inflammation is there, and how this is just a great tool, for your veterinarian, when you have an animal with skin disease.
Conclusion and Resources
We’re going to talk lots more about testing and treatment, in upcoming episodes, so be sure to subscribe. You can also follow us on social media, and if you’re local to Los Angeles, you can make an appointment with me, or the other fabulous dermatologists at Veterinary Skin and Ear. If you’re looking for a veterinary dermatologist in your area, check out the resources tab on the website, and there is a link to find a specialist.
Scratching the Itch: Smarter in Seconds
I like to end each episode with a segment called Scratching the Itch. This segment is designed to highlight something, whether it’s a product, a website, or a human interest story that provides a relief or just makes you feel good. Hence, scratching the itch. Today’s ‘scratching the itch’ is a viral web series called Smarter in Seconds, by the brilliant and engaging educator, Blair Imani. Smarter in Seconds teaches intersectionality, gender studies, race and racism, sociology, and United States history, in a format that is accessible. Her delivery promotes curiosity and personal growth. I follow her on Instagram, but also has a website, and is the author of several books, including Read This to Get Smarter About Race, Class, Gender, Disability, and More. We need more educational content like Smarter in Seconds, to help us become and raise a new generation of knowledgeable, inclusive allies for marginalized members of our communities.
Thanks for listening and be sure to join me again for upcoming episodes, where I’ll talk about testing and treatment of allergies in cats, and you’ll hear a lot more about Otto and how he regrew his pants.
References:
- Santoro, D., Pucheu-Haston, C.M., Prost, C., Mueller, R.S. and Jackson, H. (2021), Clinical signs and diagnosis of feline atopic syndrome: detailed guidelines for a correct diagnosis. Vet Dermatol, 32: 26-e6. https://doi.org/10.1111/vde.12935
- Waisglass SE, Landsberg GM, Yager JA et al. Underlying medical conditions in cats with presumptive psycogenic alopecia. J Am Vet Med Assoc 2006; 228: 1,705–1,709
