Skin lesions are defined as any changes to the skin such as ulcerations, wounds, cysts, papules, plaques, nodules, blisters, erosions, sores, hives or scales.
Most skin lesions are benign, but a small number can be cancerous, which is why it is always important to have any skin lesions checked out by a veterinarian.
Skin lesions can occur on any part of the body, they may be small, large, singular or multiple. Hair loss or thinning are also common when skin lesions are present.
What causes skin lesions?
There are many, many causes of skin lesions in cats, common causes include:
- Ringworm - A fungal infection of the skin characterised by raised, reddened patches, typically with hair loss.
- Allergies - There are many causes of allergies in cats from insect bites and stings to food, chemicals, shampoos, pollens. All of which can cause rashes and itchiness in cats.
- Flea allergy dermatitis - Another type of allergy, which is due to the saliva the flea injects into the cat's skin.
- Abscess - An abscess usually occurs as a result of a bite from another cat. The area becomes infected with bacteria. The body attempts to contain the infection by walling off the area. This becomes filled with pus. Eventually, the abscess will rupture and drain. Abscesses are typically firm, round lumps under your cat's skin. He may also have a fever and experience pain in the area.
- Mites - There are a number of types of mites which can infect cats including scabies, demodicosis, walking dandruff, chiggers (harvest mites) and ear mites. Symptoms of mites include intense itching, swelling, crusty lesions.
- Feline acne - Characterised by the presence of comedones (blackheads) on the chin, itching, inflammation and lesions may occur due to itching and rubbing of the affected area.
- Folliculitis - Infection or inflammation of the hair follicle characterised by redness, inflammation and lesions of the affected area.
- Miliary dermatitis - A disease complex characterised by the presence of a crusty rash around the head, neck and back. There are many causes of this including flea allergies, infections, hormonal disorders, diet, mites and mange.
- Tumours - These may be benign (non-cancerous) such as sebaceous cysts or cancerous. The most common sign is a lump on the skin which may be open and weeping.
- Skin infections - Usually caused by either an injury to the skin which becomes infected, skin infections are most commonly caused by the staphylococcus bacteria.
- Bubonic plague - A zoonotic infection (transmissible from cats to humans) caused by the bacteria Yersinia Pestis, bubonic plague is one form of the "plague" which affects the lymph nodes. These become swollen and eventually abscessed, loss of appetite, depression, lethargy and fever are also symptoms. Thankfully the bubonic plague is relatively rare these days.
- Burns (thermal, electrical or chemical) - Electrical burns most often happen around the mouth, due to cats chewing on electrical cords. Thermal (from heat, liquids or fire) can occur on any part of the body, they're most often associated with jumping onto a hot surface such as a stove, or accidental burns from open flames. Chemical are rare in cats and are more often than not associated with ingestion of chemicals such as bleach.
- Antiparasitic products such as flea collars and topical flea treatments can cause irritation and open wounds to develop on the area.
- Frostbite - Damage to the skin due to exposure to extreme cold.
- Eosinophilic granuloma complex - Eosinophilic granuloma complex (EGC) is a condition characterised by the presence of skin lesions over various parts of your cat's body. Caused by cells known as eosinophils which usually target parasites and microorganisms, but in this syndrome, they are called to the site of an allergic reaction (such as a flea bite), releasing their cytotoxic granules causing lesions in the affected area. There are three types, all of which affect different parts of the body. Indolent (or rodent ulcer) which affect the lip, eosinophilic plaque in which lesions are most often seen on the thighs or abdomen and eosinophilic granulomas which are commonly found on the rear legs and are seen most often in young (under two) cats.
- Blastomycosis - A fungal infection caused by Blastomyces dermatitidis. Immunocompromised cats are at greater risk of infection. Common symptoms include coughing, difficulty breathing, enlarged lymph nodes, lethargy, weight loss, ocular discharges and skin lesions.
How are skin lesions diagnosed?
Your veterinarian will perform a physical examination of your cat, obtaining a medical history from you. The cause can be narrowed down depending on how the lesion(s) appears, accompanying symptoms etc, the location. He may need to run further tests such as:
- Skin scrapings - To check for mites.
- Biopsy - To evaluate for cancer.
- Bacterial and/or fungal culture.
- Food elimination trial, where your cat is placed on a "novel" diet to see if the lesions go away, he will then be challenged by going back on his regular diet to see if they return.
- Skin patch tests - To check for common allergies such as dust mites, pollen.
How are skin lesions treated?
Treatment of skin lesions depends on the underlying cause and may include:
- Lime sulfur dips to treat mites.
- Antibiotics to treat skin infections, abscesses.
- Surgical removal of benign or cancerous tumours.
- Finding and removing the source of allergens. Which may include switching diet.
- Switching anti-parasitic products.
- Corticosteroids may be prescribed to treat inflammation.
- Cleaning acne affected skin, switching to ceramic or metal food bowls.