If you wake up one day to see your cat’s lip enlarged and swollen you will probably want to know right away what’s happening. One cause is by far the most frequent reason for swollen lips in cats.
Table of Contents
The number one cause of lip swelling in cats
The most common cause for a swollen lip in a cat is a feline allergic skin reaction called eosinophilic granuloma complex. Eosinophilic granuloma complex (ECG) in cats causes the tissue to become infiltrated with an allergy cell called an eosinophil. A common spot for this to occur is in the lips of cats and is generally not painful or itchy. Other areas of the body commonly affected are on the roof of the mouth, the abdomen and thighs. Eosinophilic plaques on the belly or thighs can be very itchy.
Eosinophils act as part of the immune system and they primarily act to defend against parasites. They are white blood cells attracted to areas where parasitism occurs. Eosinophils release chemicals to destroy the perceived invader. In some cats, their immune systems react to pollen, dust, flea bites, grain mites or food proteins as “foreign invaders”. Eosinophils aggregate and release histamine which causes swelling and redness and sometimes causes itchiness. A large grouping of eosinophils within the skin will cause a lump or solid swelling.
Cats who develop swelling of their lip due to eosinophilic granuloma complex can vary a lot in regards to how severely their lip will swell. In some cats, the swelling is only a mild puffiness. However, other cats may have wide, firm infiltration of their lips which can severely deform their face. Treatment can reduce the swelling, but if the swelling is substantial, there can be destruction of the tissue. This may lead to scarring and an altered facial feature.
Most of the time, the swelling and ulceration affects the upper lip near the philtrum, near where the canine or fang teeth are located. Swelling of the upper lip in cats is sometimes referred to as a “rodent” ulcer. The swelling can alter a cat’s facial features and make them look more like a rodent with a puffy lip. Upper lip swelling may be bilateral or unilateral. The upper lip can become firm and thickened with a yellow to white surface from secondary infection.
The allergic swelling sometimes only affects the central lower lip causing it to look fat or enlarged.
Diagnosing eosinophilic granuloma complex in cats
Lesions can be identified as an eosinophilic granuloma complex (ECG) lesion by taking an impression smear of the lesion or a needle biopsy sample to identify a preponderance of eosinophils. This investigation can also be used to determine if there is a secondary bacterial infection.
In some patients a tissue biopsy may be recommended to determine if the skin signs are due to ECG. Blood screening to identify an elevated blood eosinophil count may be recommended.
Many times the characteristics of the skin signs are enough to provide a tentative diagnosis of eosinophilic granuloma complex in cats. The response to therapy can further support this diagnosis.
Immunosuppressive doses of steroids to treat eosinophilic granuloma complex in cats
The most universally effective and rapid treatment response is achieved by providing immunosuppressive doses of steroids. Lesions typically regress quickly along with any other signs such as itching. Because cats that suffer from ECG typically have recurrent episodes, alternatives to frequent use of steroids is recommended. Long term or frequent use of steroids can predispose cat to the development of other diseases such as diabetes mellitus.
Steroid-sparing treatment for feline eosinophilic granuloma complex
A steroid-sparing first line treatment option is the use of an antibiotic course. A study of cats has shown that therapy with a course of amoxicillin-clavulanic acid was highly effective in reducing the size of lesions.
Most cats with ECG are treated with multi modal therapy to address multiple triggers for this immune disregulation. Two mainstays of therapy revolve around treating and preventing fleas, mites and lice and feeding a hypoallergenic diet.
To exclude the possibility of grain mite allergy, an all canned food hypoallergenic diet can be fed.
Bravecto and Revolution are great flea preventatives for cats that treat and present fleas as well as lice and some mites.
Bravecto lasts 12 weeks in a single use which is easy on owners. Another benefit of Bravecto is that it can be used off label to treat demodex gatoi in cats, the demodex mite of cats that causes a marked allergic response.
The most common triggers for feline lip swelling
- Food allergy
- Grain mite allergy
- Flea allergy
- mosquito bite hypersensitivity
- Environmental allergies ( pollens, mold, dust, etc.)
Prevention of lip swelling in cats
Preventing eosinophilic granulomas in cats relies on reducing allergy triggers. Cats that live in households with multiple cats or are outdoor cats are at increased risk for flea bite allergy. Regardless, any cat with an allergy based skin eruption should be prophylactically treated with a flea preventative. A single flea bite can trigger an allergy response. Cats with lip swelling may also benefit from a hypoallergenic diet trial. Blood and skin testing for food allergy is not reliable, so dietary trials are necessary.
Use flea prevention in all cats with allergic lip swelling
All animals in the house should be treated with flea preventative. Any signs of flea infestation will warrant treatment of the home with an adulticide and an insect growth regulator after thorough cleaning of the home. I typically choose to put cats on routine use of feline Revolution Plus to treat and prevent flea and mite infections. Another good option is Bravecto Plus which is effective for fleas, ticks and lice.
Feline hypoallergenic diet trial
A feline hypoallergenic diet trial consists of a minimum of 4-6 weeks on a novel protein diet or a hydrolyzed diet. A novel protein diet is a diet containing a protein never consumed by the cat before. Some foods utilize unusual proteins like rabbit and kangaroo and venison to offer a diet that contains a protein a cat has not consumed in the past. Any two proteins in a similar taxonomic category such as turkey and chicken may cause a cross reaction. It is most ideal to pick proteins that are very different.
Feline hydrolyzed hypoallergenic diets
Hydrolyzed prescription foods may be easiest to choose.
A hydrolyzed diet is a prescription diet that has all proteins broken down into tiny molecular weight pieces that are too small for detection by the immune system. These diets can be based on a protein a cat may have eaten in the past such as chicken, but the proteins are hydrolyzed.
Feline grain mite allergy
Food storage mites are present frequently in dry pet foods, grains, cereals and some cheese and may trigger and allergy in cats. Feeding an all canned diet is the treatment of choice. Since it can be hard or expensive to try to identify a grain storage mite, a good solution is to change your cat’s diet to a hypoallergenic canned food diet.
Good hypoallergenic diet choices for cats
- Purina Pro Plan HA diet : soy , hydrolyzed chicken, salmon
- Royal Canin HP hydrolyzed soy and chicken fat
- Royal Canin Ultamino diet with hydrolyzed poultry by-products
- Hills z/d diet hydrolyzed chicken
- Blue Natural HF hydrolyzed salmon, potato and pea
- Novel Protein diets such as Natural Balance which is available without a prescription on Amazon
Rabbit, venison, duck.
Allergen immunotherapy for cats is highly successful
If flea allergy and food allergy treatment fails to prevent further eruptions, environmental allergies may be the cause. Skin testing is the most reliable way to identify the environmental causes of allergies. Although blood panels for allergens exist for cats, they have not proven to be reliable. A battery of skin tests to common local allergens (dusts,molds, dander, grasses, pollens etc.) will inform the veterinarian about allergen triggers.
Allergen-specific immunotherapy (ASIT) is the practice of gradually providing increasing amounts of an extract of an allergen. This is delivered either by injection or via liquid drops under the tongue in order to reduce a cat’s sensitivity to that allergen.
The cocktail of allergens used for desensitization is tailored to the individual cat. The practice of allergy desensitization has a roughly 75% success rate in cats!
Unfortunately, this option is less frequently pursued by owners probably because it requires a time commitment to determine the “offending” allergens and deliver regular frequent dosing of the allergen in gradually increasing amounts over a period of several months to a year.
This service that is routinely provided by veterinary dermatologists. If you are interested in finding a veterinary dermatologist, you can find one here.
Although eosinophilic granuloma complex is the most common cause of lip swelling in cats, other causes should be excluded.
Other possible causes of lip swelling in cats
- Demodex mite skin infection
- Lip bacterial infection
- Chin acne
- Viral infection (herpes, calici)
- Squamous cell carcinoma
- Glandular cystic swelling
Demodex Gatoi skin infections in cats
Demodex is a skin mite that is present in the hair follicle in cats. Demodex cati is a normal commensal organism on the skin and typically does not cause skin infections except in immunocompromised cats. It is not contagious to other cats. There is another demodex organism (demodex gatoi) that can cause marked itch that can drive some cats to over groom their coats (“fur mowing”). Demodex gatoi infections on the face can cause marked inflammation and itch.
Some cats will develop red inflamed skin irritation (eosinophilic granuloma complex) or tiny seed-like scabs on their body (called military dermatitis).
Demodex gatoi in cats was historically best treated with smelly sulfur dips (bathing). However, now, Bravecto ( tosspot solution for cats) is being utilized in some shelters.
Feline chin acne
Chin acne is a fairly frequent skin infection seen in cats caused by hair follicles clogged by oils. This creates comedones on the chin and these can sometimes extend to near the lower lips. You can use salicylic acid in Stridex pads to wipe your cat’s chin.
Benzoyl peroxide has good follicular flushing action and can be applied as a wash or a gel. A benzoyl peroxide gel is available on Amazon.
Feline bacterial lip fold infection
Sometimes cats and dogs can develop a bacterial skin infection along the sides of their mouth, where their lips meet. This is called the lip commissure and this location can be prone to skin inflammation secondary to a viral infection like herpes virus and cause localized inflammation and secondary bacterial infection. It may also be a flare up of allergies causing eosinophilic infiltrates along the mucocutaneous junction of the lips (eosinophilic granuloma complex).
Feline viral infections causing oral lesions
Herpes virus can be treated with oral antiviral therapy with a drug called Famciclovir. This skin infection may also resolve without an antiviral by just treating the secondary skin infection with an oral antibiotic.
Herpes can also cause other scabby skin lesions on the face such as on the nose or around the eyes.
Other viral infections in cats can cause oral lesions. The most common viral cause for characteristic oral lesions is Calicivirus. Calicivirus most commonly causes erosive lesions on the tongue. Calicivirus typically causes a respiratory tract infection and additionally lesions may be noted in the mouth. There is no treatment for calicivirus but most cats will recover completely. It is far more common in kittens than in adult cats. The FVRCP feline vaccine cannot prevent calicivirus infections but does help to reduce the severity of calicivirus infections in cats.
Squamous cell carcinoma of the mouth in cats
Squamous cell carcinoma is the most commonly encountered malignant oral tumor in cats. It less commonly affects the lips however. More typical locations are on the gum tissue or mucosal surfaces of the upper or lower jaw, under the tongue or by the tonsils. This tumor is expected to grow larger over time and be locally destructive to the surrounding tissue by creating a firm mass. There is often ulceration and infection of the tissue as well. Squamous cell carcinoma of the mouth carries a very poor prognosis unfortunately as most are not identified early enough. Treatment involves surgical removal and radiation therapy.
Squamous cell carcinoma of the lip
Cystic bumpy swelling of the lips in cats
Some cats develop bumpy pigmented skin nodules along their lips that can cause swelling and changes to the lip contour. They are called apocrine gland hidrocystomas. These are benign nodules and not cancerous.
Conclusion
While Eosinophilic granuloma complex of the cat is the most common cause of lip swelling in cats, there are many other possibilities to be considered. Always check with your veterinarian if you have concerns about your cat’s health.