Cats are susceptible to a number of skin conditions, and as many skin diseases have similar symptoms. In order to determine the type and underlying cause of the skin problem, a number of 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, including onset of symptoms, if they are seasonal, if the cat is on any medications, and what parasite control is used on the cat. The type of test will be determined based on presenting symptoms.
Common symptoms of skin conditions include:
- 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
Fleas are a common parasite in cats and many will develop an allergy to the flea saliva which is injected into the skin when the flea feeds.
The flea comb is the fastest, easiest and cheapest diagnostic tool in the veterinary dermatologist’s arsenal. This fine-toothed comb is run through the cat’s coat to pick up fleas.
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 is 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 in order to encourage fungal growth. It can take several weeks to obtain results.
Food elimination trial
Diagnosis: Food allergies
The cat is switched to 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 a number of 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 is used to remove larger skin samples, such as lumps on or under the skin.