Last Updated on June 20, 2021 by Julia Wilson
Cats are susceptible to several skin conditions, and many skin diseases have similar symptoms. To determine the type and underlying cause of the skin problem, several diagnostic tests are available. We look at common tests used to diagnose skin conditions in cats.
The veterinarian will perform a physical examination of the cat and obtain a medical history from you; questions may include:
- When did symptoms develop?
- Are symptoms seasonal?
- Is the cat on any medication?
- What parasite treatment are you using?
Symptoms of skin diseases in cats
- Lumps and bumps
- Miliary dermatitis (firm, scabs often located on the cat’s back, close to the base of the tail)
- Scabs (especially on the neck and back)
- Hair loss
- Excessive grooming
- Patches of red or scaly skin
- Fleas or flea dirt in the coat, or salt and pepper debris (flea eggs and feces) in or around the cat’s sleeping area
Diagnosing skin diseases
Fleas are a common parasite in cats, and many will develop an allergy to flea saliva when the flea feeds on the cat.
The flea comb is the fastest, easiest and cheapest diagnostic tool in the veterinary dermatologist’s arsenal. The veterinarian runs the comb through the coat to pick up fleas or flea debris.
Wood lamp examination
A simple way to diagnose ringworm is to use an ultraviolet Wood’s lamp (also known as a black light) on your cat, although only around 50% of ringworm strains will show up. The infected hair shafts will glow a fluorescent green when exposed to a Wood’s lamp.
A skin scraping test is a simple diagnostic test in which a sample of skin cells, hair follicles, and hair samples are obtained using a scalpel blade scrape to scrape through the epidermis and down to the dermis. It is necessary to scrape deep enough to reach mites, which often burrow quite deeply. You will see a small amount of blood as a result. The sample is then evaluated under a microscope (cytology).
Diagnosis: Microsporum spp. (ringworm) and Trichophyton spp.
The veterinarian gently scrapes the surface of the skin with an unused toothbrush or plucks out some hairs from the affected area to obtain a sample. The sample is placed onto a culture medium which is stored in a dark and warm location to encourage fungal growth. It can take several weeks to obtain results.
Food elimination trial
Diagnosis: Food allergies
The cat is fed a novel source of protein (duck, lamb, kangaroo) for several weeks to see if symptoms resolve. At this time, no other food (including treats) can be given to the cat. If symptoms improve after the trial, the cat is challenged, by slowly re-introducing the cat’s normal diet, one by one.
Intradermal skin testing
This test involves injecting a small amount of several common allergens such as dust mites, pollens into an area of shaved skin on the side or belly. The area is evaluated 24-48 hours. If the cat has an allergy to any of these substances, swelling and redness will develop at the site of the specific allergen.
Fine needle aspiration
Diagnosis: Tumours and cysts
A fine needle is used to obtain a small sample of mass or cyst to obtain a small sample of cellular material for microscopic evaluation (cytology).
Diagnosis: Pemphigus, eosinophilic granuloma complex, tumours, acne, systemic lupus erythematosus, allergies, fungal infections, cowpox, and many more skin conditions.
A biopsy involves the surgical removal of a small sample of skin (or other tissue) which is evaluated under a microscope. There are two main types of skin biopsy, punch, and scalpel.
- A punch biopsy uses a circular punch tool to remove a small section of skin.
- The scalpel will be necessary to remove large skin samples, such as lumps on or under the skin.