Initial Testing for Infectious Skin Diseases in Pets

By: Molly Price, DVM

TVMA Member
Belize, Central America

Published December 2017

Red, itchy, crusty or flaky skin and hair loss are common skin problems in dogs and cats. As a result of these skin conditions, pets scratch, lick or chew on themselves, often causing everyone to lose sleep. If your pet is showing these signs, take your pet to the veterinarian for a thorough examination. Your veterinarian will perform simple in-house tests to determine if your pet has any infections (bacterial, yeast or ringworm) or parasites (mites, fleas, etc.).

Physical Examination

Your veterinarian will thoroughly examine your pet, especially paying attention to the appearance and pattern of your pet’s abnormal skin lesions, as well as looking for ticks, live fleas or “flea dirt” (flea feces).

Skin and Ear Cytology

Cytology means an analysis of cells. Impression smears allow veterinarians to take samples of your pet’s skin by painlessly pressing a glass slide against the abnormal area of skin or by using a cotton-tipped applicator or a small piece of tape. Then your veterinarian will examine the slide for bacteria and yeast. If your pet has an ear infection, your veterinarian will take a sample of the abnormal discharge in the ear and examine the debris for ear mites, bacteria and yeast organisms.

Skin Scraping

Your veterinarian will gently scrape your pet’s affected area of skin with a small amount of oil and a blade to check for mites, such as Demodexa genus of tiny mites that live in or near hair follicles of mammals, Sarcoptes and Notoedres.

Wood’s Lamp Exam and DTM

Your veterinarian will pluck hairs from your pet’s fur to perform a fungal culture using a dermatophyte test medium (DTM) plate or jar and conduct a Wood’s lamp examination, which involves shining a specially coated fluorescent light on your pet’s fur. The DTM and Wood’s lamp exams test for a fungal infection called dermatophytosis, commonly known as ringworm. Next, your veterinarian will check the DTM daily for growth of fungus for up to two to three weeks. If the DTM is positive for growth, your veterinarian will examine small pieces of the material under a microscope to identify which fungus is the cause of the problem.

Running these basic diagnostic tests is a great way for your veterinarian to discover if your pet has any parasites or infections associated with their skin or ear problem. Having an exact diagnosis helps your veterinarian treat your dog or cat with the most appropriate and effective medications, helping your pet feel better as quickly as possible!


Molly Price, DVM, is a graduate of Texas A&M University College of Veterinary Medicine who lives in Allen, Texas. She is a relief veterinarian and is enthusiastic about educating clients and staff members.

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