# Eosinophilic Stomatitis in Dogs: Mouth Sores and Treatment Eosinophilic stomatitis in dogs is a rare immune-mediated condition that causes painful sores, plaques, or nodules in the mouth. It happens when the immune system overreacts, often to insect bites or other allergens, and sends a type of white blood cell called eosinophils into the oral tissues. Because the sores hurt, dogs may drool, drop food, or stop eating, so early veterinary care matters. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Eosinophilic stomatitis is rare in dogs and is linked to unusual hypersensitivity (allergic) reactions, often to insect bites [1]. - Sores can look like raised bumps, plaques, or ulcerated masses on the lips, gums, or inside the cheeks [2][1]. - Diagnosis usually requires a tissue biopsy, because these lesions can look like other oral diseases [2]. - Corticosteroids are the mainstay of treatment, and insect control helps if bites are the trigger [1]. - Many dogs improve with treatment, but some need long-term low-dose medication to stay comfortable [1]. ## What Is Eosinophilic Stomatitis in Dogs? Stomatitis means inflammation of the mouth. Eosinophilic stomatitis means that inflammation is driven by eosinophils, a type of white blood cell involved in allergic reactions and parasite defense. In dogs, these lesions are grouped under a broader term called eosinophilic granuloma complex. This complex is rare in dogs and much more common in cats and horses [1]. When it does appear in a dog, it is usually tied to a hypersensitivity reaction, meaning the immune system reacts too strongly to something like an insect bite [1]. The lesions themselves are described histologically (under the microscope) as eosinophilic granulomas. In the mouth, they can show up as ulcerated or vegetative masses, or as raised plaques or nodules [2]. "Vegetative" means the tissue looks fleshy and overgrown. These are not cancer, but they can look like it, which is one reason a biopsy matters. Eosinophilic stomatitis is sometimes discussed alongside other severe oral inflammatory conditions in dogs, including canine chronic ulcerative stomatitis (CCUS) and Wegener's granulomatosis [3]. These conditions can look similar to each other, and telling them apart often takes a biopsy and a careful oral exam. ## Signs Owners Notice The most obvious sign is mouth pain. Dogs hide pain well, so you may notice changes in eating before you ever see a sore. Watch for: - Drooling, sometimes with blood-tinged saliva - Dropping food or chewing on one side - Reluctance to eat hard kibble, or refusing food altogether - Bad breath that does not improve with brushing - Pawing at the mouth or rubbing the face - Swelling or visible red bumps on the lips, gums, or cheeks - Weight loss if eating has been painful for a while Some dogs with oral eosinophilic lesions have raised plaques or nodules that you can see if you lift the lip [2]. Others have lesions deeper in the mouth that only a veterinarian can find. If your dog has bad breath along with mouth pain, that can point to dental disease as well. You can read more about that in [Dog Bad Breath Disease](/knowledge/veterinary-medicine/dental-care/dog-bad-breath-disease) and [Dog Bad Breath Periodontal Disease](/knowledge/veterinary-medicine/dental-care/dog-bad-breath-periodontal-disease). Dental disease and eosinophilic stomatitis can occur together, and both need attention. ## Causes and Risk Factors The exact cause is not fully understood. What veterinarians do know is that these lesions are most commonly associated with hypersensitivity reactions [2]. In plain terms, the immune system is reacting to something it should not. Common suspected triggers include: - Insect bites or stings, including wasps, bees, ants, and spiders [1] - Other allergic conditions, such as environmental or food allergies [1] - An overactive immune response with no clear external trigger Any breed can be affected, but Siberian Huskies and Cavalier King Charles Spaniels may be at greater risk [1]. A closely related condition, canine eosinophilic furunculosis, is typically seen in long-nosed large breeds or curious small breeds like terriers that may have access to stinging insects [1]. Some dogs with allergic airway disease also develop eosinophilic problems elsewhere in the body. If your dog has a chronic cough along with mouth issues, [Canine Eosinophilic Bronchopneumopathy: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/canine-eosinophilic-bronchopneumopathy-diagnosis-management) explains a related eosinophilic condition in the lungs. ## How Eosinophilic Stomatitis in Dogs Is Diagnosed Diagnosis starts with a full oral exam. Your veterinarian will look at the lips, gums, tongue, palate, and back of the throat. Many dogs need light sedation for a thorough look, because a painful mouth is hard to examine on a awake patient. ### Biopsy Is Usually Needed The single most useful test is a tissue biopsy. Eosinophilic granulomas in the mouth can look like ulcers, plaques, or fleshy masses, and they can resemble other conditions, including cancer [2]. A biopsy lets the pathologist see the eosinophils and confirm what is going on. ### Other Tests Your Veterinarian May Run - Cytology, where cells are collected and examined under a microscope. In related eosinophilic skin and nasal diseases, cytology shows eosinophils [2]. - Blood work to check overall health and rule out other causes. - Dental radiographs (X-rays) to look for periodontal disease or tooth root problems. - Allergy testing or a food trial if an allergic trigger is suspected. Your veterinarian may also consider other severe oral inflammatory diseases, such as CCUS, which is a painful and often debilitating condition with a suspected immune-mediated component [4]. Because these conditions can overlap, a clear diagnosis guides the right treatment. | What You May See | What It Often Means | How It Is Confirmed | |---|---|---| | Raised bumps or plaques on lips or gums | Eosinophilic granuloma complex | Biopsy [2][1] | | Ulcerated or fleshy mass in the mouth | Eosinophilic lesion or other oral disease | Biopsy [2] | | Red, swollen muzzle with rapid onset | Eosinophilic furunculosis (related condition) | Clinical signs and cytology [2] | | Gum inflammation with bad breath | Periodontal disease, possibly alongside stomatitis | Oral exam and dental X-rays | ## Treatment Options Treatment aims to calm the immune reaction, control pain, and remove any trigger. Your veterinarian will tailor the plan to your dog. ### Corticosteroids Corticosteroids are the first-line treatment for most eosinophilic lesions. Some cases can be treated with corticosteroids, and if the disorder returns, low-dose corticosteroid treatment may be prescribed [1]. These drugs reduce inflammation and suppress the overactive immune response. Never give your dog steroids from your own supply or from a previous prescription. Your veterinarian calculates the dose from your dog's weight and health, and the dose is often tapered slowly over weeks. ### Insect Control If insect bites are the trigger, insect control may be of some value [1]. That can mean keeping your dog away from known nests, using veterinarian-approved parasite prevention, and checking the yard for wasps or ants. ### Antibiotics and Allergy Management When a related condition, eosinophilic furunculosis, is present, treatment consists of insect control, management of any associated allergies, antibiotics, and corticosteroids [1]. Antibiotics treat secondary bacterial infection in damaged tissue, not the immune problem itself. ### Other Immune-Modulating Drugs For severe or stubborn oral inflammation, veterinarians sometimes use other immune-suppressing medications. In one study of dogs with CCUS, a combination of cyclosporine at 5 mg/kg for one week followed by the addition of metronidazole at 15 to 20 mg/kg, both given by mouth once daily, was evaluated for managing the condition [4]. This is a specific protocol from a research setting, so ask your veterinarian whether a similar approach fits your dog. ### Dental Care and Extractions Some dogs with oral inflammation have contact lesions from periodontal disease. A 2025 review of 42 dogs with lymphoplasmacytic stomatitis found that only a minority may need full-mouth extractions, which is different from the approach used in cats [5]. That means surgery is not automatic for every dog with mouth inflammation. Your veterinarian will decide based on where the lesions are and how your dog responds to treatment. Good home dental care supports healing. [How To Treat Gum Disease In Dogs](/knowledge/veterinary-medicine/dental-care/how-to-treat-gum-disease-in-dogs) covers brushing, dental diets, and professional cleanings. ### Pain Control and Nutrition A dog that will not eat needs help fast. Soft food, warmed food, and appetite support can keep nutrition up while the mouth heals. Your veterinarian may prescribe pain medication. Do not give human pain relievers, since many are toxic to dogs. ## Recovery, Outlook, and Long-Term Management Most dogs improve with treatment, but this condition can come back. If the disorder returns, low-dose corticosteroid treatment may be prescribed [1]. That means some dogs stay on a small maintenance dose long term. Expect recheck visits. Your veterinarian will want to see the mouth healing, check that your dog is eating, and adjust medication. Blood work may be repeated if your dog is on immune-suppressing drugs for months. Some oral inflammatory conditions in dogs respond poorly to medication, which is why veterinarians keep looking for better options [4]. If your dog does not improve on the first plan, that does not mean treatment has failed. It means the plan needs adjusting. Watch for these long-term issues: - Weight loss from chronic pain while eating - Return of sores after the steroid dose is lowered - Secondary bacterial infections - Dental disease that worsens because your dog avoids chewing Keep a simple log of what your dog eats, how long meals take, and any drooling or head shyness. That record helps your veterinarian judge whether treatment is working. ## Prevention You cannot always prevent an immune-mediated disease, but you can lower known triggers. - Control insects. Reduce standing water, seal trash, and check for nests around your home [1]. - Manage allergies. Work with your veterinarian on food trials or allergy treatment if a trigger is suspected [1]. - Keep up dental care. Regular brushing and professional cleanings reduce oral inflammation from periodontal disease. See [How To Treat Gum Disease In Dogs](/knowledge/veterinary-medicine/dental-care/how-to-treat-gum-disease-in-dogs). - Check the mouth monthly. Lift the lips and look for new bumps, redness, or ulcers. - Address licking and chewing. If your dog licks or chews at the face or paws until sores form, [Dog Licking Paws Causing Sores](/knowledge/veterinary-medicine/clinical-methods/dog-licking-paws-causing-sores) explains why that habit needs a veterinary workup. ## Limitations and When to Contact a Veterinarian No article can diagnose your dog. Eosinophilic stomatitis is rare, and many other conditions cause similar mouth sores. Your dog needs a veterinarian who can examine the mouth and, in most cases, take a biopsy. Contact your veterinarian the same day if you notice: - Drooling that started suddenly - Your dog dropping food or refusing to eat - A visible sore, bump, or swelling in the mouth - Bad breath that is new or much worse Go to an emergency clinic now if you see: - Heavy bleeding from the mouth - Trouble breathing or swelling around the throat - Your dog cannot swallow at all - Signs of severe pain, such as crying out when the mouth is touched Schedule a routine visit if your dog has a history of these lesions and you notice the first subtle signs of a flare, such as slower eating or more drooling than usual. ## Frequently Asked Questions ### Is eosinophilic stomatitis in dogs contagious to other pets? No, it is not contagious. It is an immune-mediated reaction in your dog's own body, not an infection that spreads to other animals [1]. Other pets in the home do not need to be separated. ### Can this condition be cured, or will my dog need treatment forever? Some dogs go into remission and can stop medication. Others need low-dose corticosteroid treatment long term if the disorder returns [1]. Your veterinarian will guide the taper based on how your dog responds. ### Does my dog need all of its teeth removed? Usually not. A review of surgically treated dogs with oral inflammation found that only a minority may require full-mouth extractions [5]. Extractions are considered when specific teeth or contact lesions are driving the problem. ### Are certain breeds more likely to get eosinophilic mouth lesions? Yes. Any breed can be affected, but Siberian Huskies and Cavalier King Charles Spaniels may be at greater risk [1]. Breed alone does not cause the disease, but it can raise suspicion when mouth sores appear. ### Can I use human steroid creams or pills on my dog's mouth sores? No. Never use human medications without veterinary direction. Your veterinarian calculates the correct drug and dose from your dog's weight and health, and some human products are toxic to dogs. ## Related Articles - [Canine Eosinophilic Bronchopneumopathy: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/canine-eosinophilic-bronchopneumopathy-diagnosis-management) - [How To Treat Gum Disease In Dogs](/knowledge/veterinary-medicine/dental-care/how-to-treat-gum-disease-in-dogs) - [Dog Licking Paws Causing Sores](/knowledge/veterinary-medicine/clinical-methods/dog-licking-paws-causing-sores) - [Dog Bad Breath Disease](/knowledge/veterinary-medicine/dental-care/dog-bad-breath-disease) - [Dog Bad Breath Periodontal Disease](/knowledge/veterinary-medicine/dental-care/dog-bad-breath-periodontal-disease) - [Canine Polymyositis: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/canine-polymyositis-diagnosis-management) - [Stomatitis in Dogs: Mouth Symptoms and Causes](/knowledge/veterinary-medicine/dental-care/stomatitis-dogs-symptoms-causes) - [Ulcerative Stomatitis in Dogs: Mouth Ulcers Explained](/knowledge/veterinary-medicine/dental-care/ulcerative-stomatitis-in-dogs) - [Chronic Stomatitis in Dogs: Causes and Treatment](/knowledge/veterinary-medicine/dental-care/chronic-stomatitis-in-dogs) ## References 1. [Eosinophilic Granuloma Complex in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/eosinophilic-granuloma-complex-in-dogs). Merck Veterinary Manual. 2. [Eosinophilic Lesions in Dogs - Integumentary System](https://www.merckvetmanual.com/integumentary-system/eosinophilic-inflammatory-skin-diseases/eosinophilic-lesions-in-dogs). Merck Veterinary Manual. 3. [Management of Severe Oral Inflammatory Conditions in Dogs and Cats](https://pubmed.ncbi.nlm.nih.gov/34838249/). The Veterinary clinics of North America. Small animal practice, 2022. 4. [Medical Management of Canine Chronic Ulcerative Stomatitis Using Cyclosporine and Metronidazole](https://pubmed.ncbi.nlm.nih.gov/36650996/). Journal of veterinary dentistry, 2023. 5. [Surgical outcomes in canine lymphoplasmacytic stomatitis: a retrospective study of 42 dogs (2012-2022)](https://pubmed.ncbi.nlm.nih.gov/41445593/). Frontiers in veterinary science, 2025. ## Further Reading - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)