Skin Lesions on Cats

Last Updated on July 3, 2021 by Julia Wilson

What are skin lesions?

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 is also common when skin lesions are present.

Causes

There are many, many causes of skin lesions in cats which can include parasites, allergies and infections.

Ringworm

A highly contagious 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 itching, rashes, hair loss and trauma due to constant scratching. 

Flea allergy dermatitis

Flea allergy dermatitis is a common allergy caused by proteins in the saliva of the flea that is injected into the skin when the flea feeds on the cat. Miliary dermatitis is the most common manifestation of FAD, which typically affects the back, towards the tail and around the neck. 

Abscess

An abscess usually occurs as a result of a bite from another cat. The area becomes infected with bacteria and the body attempts to contain the infection by walling off the area which becomes filled with pus. Eventually, the abscess will rupture and drain. Abscesses are typically firm, round lumps under your cat’s skin, the cat may also experience pain and fever. 

Mites

There are several types of mites that 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

Feline acne is a common skin disorder characterised by the presence of comedones (blackheads) on the chin, itching, inflammation, and lesions that may occur due to itching and rubbing of the affected area. 

Folliculitis

An 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

Tumours are abnormal growths that can be benign (non-cancerous) such as sebaceous cysts or cancerous. The most common symptom of a skin tumour is a lump on the skin which may be open and weeping.

Skin infections

Also known as pyoderma (which stands for pus in the skin) skin infections are relatively uncommon in cats. Most skin infections are secondary, which means they are caused by an underlying disorder. Anything that affects the integrity of the skin has the potential to lead to a skin infection. Most often this is caused by trauma (such as a bite or scratch), self-mutilation, over-grooming but more often than not, skin infections are caused by self-trauma from biting or scratching itchy skin.

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.

Diagnosis

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.

Diagnostic workup:

  • Skin scrapings – A scalpel is used to scrape along the surface of the skin to obtain a sample which will be evaluated under a microscope. 
  • Biopsy – A skin biopsy involves the removal of a tumour, which is sent to a laboratory to determine which cells are involved and if it is benign or malignant. 
  • Bacterial and/or fungal culture and sensitivity – A sample of a lesion is obtained and grown to identify the organism, sensitivity involves exposing the cultured organism to several antibiotics or antifungals to determine which is the most effective at killing the pathogen. 
  • Food elimination trial – The cat is placed on a novel diet such as goat or kangaroo for six weeks, with no other types of food offered, to see if the lesions go away.  After the trial, the cat is challenged to see if symptoms return. 
  • Skin patch tests – This test applies a number of common allergens to a shaved area of the skin to see if there is a local reaction to one or more, which can diagnose common causes of allergies in cats.

Treatment

Treatment of skin lesions depends on the underlying cause and may include:

Ringworm

Medicated shampoos or dips as well as thoroughly decontaminating the home. 

Skin infection or folliculitis

Oral antibiotics for three to four weeks and topical antibiotics or antibiotic shampoos to soften crusts and treat the infection. 

Benign or cancerous lumps

Surgical removal is the mainstay treatment for tumours. If the lump is on a part of the body which makes it difficult to surgically remove, radiotherapy may be used to shrink the tumour. 

Bubonic plague

Oral antibiotics and supportive care. Strict quarantine is necessary for cats to prevent the spread of infection.

Allergies

Find and remove the source of allergens where possible. Antihistamines and corticosteroids can help to relieve symptoms. 

Cat fleas

Regular flea treatment of both your cat and the home.

Skin inflammation

Corticosteroids will be prescribed to relieve symptoms. 

Feline acne

Clean the chin daily with witch hazel or medicated topical solutions for more advanced cases. Switch to ceramic or metal food bowls and wash daily with warm, soapy water.

Eosinophilic granuloma complex

Eliminate the allergen if possible, keep the cat parasite free. Steroids to treat inflammation. Severe cases may need immunosuppressive drugs.

Blastomycosis

Systemic anti-fungal medication and supportive care.

Frostbite

Painkillers to relieve pain, severe cases may require surgery to remove damaged tissue

Burns

Treatment depends on the severity. Mild burns can be treated by flushing the area with cold water and applying aloe vera gel. Clean and apply antiseptic to second-degree burns. Hospitalisation, intravenous fluids, painkillers and antibiotics for third-degree burns.