At a glance
Ear edge dermatitis is a common condition in which the cat develops crusting along the ear margins.
- Ear mites
- Solar dermatitis
- Systemic lupus erythematosus
- Squamous cell carcinoma
- Sarcoptic mange
- Notoedric mange
- Insect bite or sting
This will depend on the underlying cause.
Also known as pinnae, the outer (visible) part of the cat’s ear is susceptible to developing thickening, crusting, ulceration, alopecia and scaling, which is collectively referred to as ear edge dermatitis or ear margin dermatitis.
There are several causes of crusty, scaly ears in cats, the most common causes include scabies, ear mites, allergies, sunburn, and systemic disorders. Crusty ear margins may be the only symptom your cat has, or you may notice other signs such as itching, discharge and head shaking.
Ear mites (Odotectes Cynotis) are a common parasitic mite that invades the ears, which occur in kittens most often.
- Reddish-brown discharge from the ear which may have the appearance of coffee grounds
- Itching and scratching
- Head shaking
- Ear twitching
- Ear odour
- Crusting and scaling of the ears
A tentative diagnosis can be made on symptoms; the presence of ear mites in skin scrapings will confirm the diagnosis.
Solutions to help clean the ears and remove discharge as well as an insecticide to kill the mites. Ivermectin, milbemycin (MilbeMite), selamectin (Revolution), imidacloprid (Advocate). Your veterinarian can recommend the best product for your cat.
Notoedric mange (feline scabies) is a rare parasitic infection caused by the Notoedres cati mite. This mite burrows into the cat’s skin, laying eggs along the way. Cats become infected by direct contact with an infected cat.
- Intense itching and scratching
- Crusting, particularly along the ear margins this then progresses to the face, neck and other parts of the cat’s body
- Self-mutilation can lead to redness, inflammation and bacterial infection of the skin
Diagnosis is made by the presence of mites or eggs in skin scrapings.
Dips, Ivermectin injections, or Revolution topical treatment. It may be necessary to clip long-haired cats before treatment to enhance penetration.
Demodicosis is an inflammatory skin disease in cats caused by the Demodex mite. There are two species, Demodex cati and Demodex gatoi, both of which can infect cats.
- Demodex cati is long and slim, living within the hair follicles.
- Demodex gatoi is shorter, living within the surface layers of your cat’s skin.
- Single or multiple areas of hair loss with crusting and scaly-looking patches. Head, ears, and neck are the most common areas.
- Generalised demodicosis can affect the entire body as well as the head and ears
- Waxy secretion in the ear
Diagnosis is made by skin scrapings and swabs from the ears, which are examined under a microscope to look for the presence of mites.
Lime sulfur dips to kill the mite. Other treatments include Amitraz; however, it is quite toxic to cats, so great care is essential. Treat all cats in the household.
- Small red pustules which burst open and cause thick crusty scabs, any part of the cat can be affected, but most commonly it is the ears, chest, and belly
- Intense itching and scratching
- Damage to the affected area can result in damage to the skin and secondary infection
Diagnosis of sarcoptic mange is made by a skin scraping, although it is not uncommon for a result to come back negative.
Lime sulfur dips, Ivermectin, or Revolution to kill the mites.
Ringworm in cats is a highly contagious, generally superficial fungal infection of the skin, fur, and nails that is caused by a fungus of the genus Microsporum and Trichophyton.
Infection occurs via direct contact with an infected animal or fungal spores, which are in the environment on objects, which commonly include grooming equipment, bedding, collars, and ectoparasites.
Circular, raised patches of rough and scaly skin. Ringworm can occur on any part of the cat, including the ears.
Diagnosis of ringworm is made by microscopic examination of hairs to look for the presence of fungal spores.
A fungal to diagnose the disease where samples of your cat’s hair are grown on a culture that enhances fungal growth.
Anti-fungal medications such as Itraconazole and Griseofulvin or lime sulfur shampoos and dips.
Some cats can develop hypersensitivity to insect bites, mosquitoes are the most common culprit, but any biting or stinging insect can produce a hypersensitivity. As your cat scratches, the ear can become further damaged, exposing the underlying layers to bacteria.
- Crusting around the ear margins
- Localised swelling
Diagnosis of an insect bite is usually made upon physical examination of your cat.
Apply an ice pack, cortisone cream, and if itching/swelling is a problem, an antihistamine such as Benadryl can relieve symptoms. If the area has become infected, antibiotics may need to be prescribed. Always speak to your veterinarian before medicating your cat.
Sunburn can occur in cats, particularly those who have pale skin colouring. The ears and nose are most vulnerable as they have the least amount/no hair. Prolonged exposure to the sun can lead to squamous cell carcinoma (see below).
Redness and itching, particularly around the ear margins. Over time, with repeated exposure, the skin can become thickened and crusty.
In most cases, the veterinarian can diagnose sunburn based on physical appearance and a history of sun exposure.
Antibiotics and steroid cream and. Limiting your cat’s exposure to the sun is the best preventative. Your veterinarian may recommend a topical sunscreen for your cat, do not use sunscreens for humans unless your veterinarian has said it is safe to use. Many contain zinc, which is toxic to cats.
Cats repeatedly exposed to the sun can go on to develop solar dermatitis, in which the skin has become chronically damaged.
As each summer passes, the ears become progressively worse with scaling and thickening of the skin, itchiness, and ulceration.
Squamous cell carcinoma
Squamous cell carcinoma is a malignant tumour of the skin, and one of the most common causes is excess exposure to the sun. Tumours can develop on any part of the body, but the ears, nose, mouth, and eyelids are the most common locations.
- Red and crusted sores
- Bleeding ulcers that don’t heal
- Dried areas of skin around the growth
- Hair loss in the affected area
A presumptive diagnosis is often made during the physical examination; this will be confirmed by biopsy.
Surgery to remove the affected area (partial pinnectomy) followed by chemotherapy or radiation therapy.
Analgesics to relieve pain.
Several allergies can develop in cats with a wide range of symptoms. The most common are:
- Insect – The most common insect allergy is due to flea bites. Cats can develop an allergy to any insect bite, the most common (aside from fleas) is the mosquito. Signs of mosquito bites include a red and swollen pustule at the site of the bite as well as itching and possible crusting along the ear margins
- Contact – This type of allergy occurs when the cat comes into contact with an allergic substance such as plants, wool, medications (topical), soaps, detergents, etc. Signs of contact allergy include non-seasonal itching and scratching, rash, blisters, and papules. Typical areas include the ears, underbelly, chin, and toes.
- Inhalant – As the name suggests, inhalant allergy relates to allergens, which are inhaled, such as pollens, dust mites, moulds. Symptoms include red and crusty rash, especially around the head, ears, neck, and back, itching and scratching, and hair loss.
- Food – Cats can develop allergies to any kind of food, but the most common are fish, beef, wheat, and eggs.
Diagnosis is made by food elimination trial, which involves switching your cat to a novel food to see if symptoms improve and then re-introducing the suspect food to see if symptoms return.
Skin prick tests expose your cat to multiple common allergens by injecting a tiny amount under the skin to see if there is a reaction and specialised blood tests to detect the presence of antibodies to certain allergens.
- Removal of the allergen where possible.
- Antihistamines and steroids to reduce inflammation and itching.
- Hyposensitisation in which your cat is exposed to minute amounts of the allergen to re-programme the immune system.
Autoimmune skin disorders are thankfully quite rare in cats, but pemphigus is the most common of them all. The cause isn’t fully understood, but it is thought there may be a genetic component, or it could be related to exposure to sunlight or certain medications. There are three types of pemphigus in cats ranging in severity.
- Small red spots, hair loss, and blister-like vesicles, which eventually break open and form thick, yellow crusts. The condition starts around the eyes and nose before spreading to the ears, face and other parts of the body
- Affected areas are itchy and painful
- Secondary bacterial infection may also develop
Diagnosis of pemphigus is based on punch biopsy, direct immunofluorescence to look for antibodies, and cytological examination of an intact pustule.
- Topical corticosteroids for mild cases.
- Severe and widespread cases will require oral corticosteroids. The veterinarian will prescribe a high dose until remission is achieved, and the cat will then be tapered to a maintenance dose.
Systemic lupus erythematosus
A rare autoimmune disorder that can affect several different organ systems of the cat, including the skin. Systemic lupus erythematosus (SLE) is caused by the body producing antibodies against itself (known as autoantibodies) that attack various systems, one of which may include the skin.
- Multifocal alopecia with crusty skin lesions, particularly around the ears, face and rear legs
- Oral and nasal ulcers
- Paronychia, inflammation around the claw beds
Diagnosis of SLE requires multiple tests, which may vary depending on the system affected.
- Routine tests including biochemical profile, complete blood count, and urinalysis
- Coombs test to detect the presence of antibodies in the blood
- Antinuclear test which measures antibodies to self-tissue
- Biopsy of a skin lesion
There is no cure for SLE; the goal of treatment is to relieve symptoms, which can include oral and/or topical corticosteroids to reduce inflammation and itching and limit exposure to sunlight.
A cat’s ears are prone to frostbite if they have access to outdoors in cold temperatures as they have little fur to protect them from the elements. As the temperatures drop, blood flow diverts from the extremities (including the ears) to preserve core temperature (and protect vital organs such as the heart and kidneys). Dampness can exacerbate the problem. First-degree frostbite affects the epidermis (outermost layer of the skin), second-degree frostbite affects the epidermis and the dermis, third-degree frostbite affects the epidermis, dermis, and the underlying tissue.
- The affected area will be a pale blue-white colour and cold to the touch
- If third-degree frostbite has occurred, the area may feel hard to the touch
- The cat may either feel pain in the area or be completely numb
- As the area thaws, the skin will become red and blistered
- In severe cases, the skin will turn blackened as the tissue dies
Diagnosis of frostbite is based on a history of exposure as well as physical signs.
- Carefully warming the affected area with warm (not hot) towels, helps to restore circulation
- If the cat is in pain, the veterinarian can prescribe painkillers
- Antibiotics to prevent secondary bacterial infection
- Surgical removal (debride) of tissue that has died