Pruritus, or itching, in dogs and cats can involve not only scratching but also licking, chewing, or biting at the skin. Pruritus is the most common symptom of skin disease in veterinary medicine. Many conditions can cause pruritus in a pet, including allergies, fleas, and other skin parasites.

There are many medications to manage pruritus. However, unless the underlying cause of the pruritus is diagnosed and addressed, the pruritus will return when the medication is stopped. Additionally, some anti-pruritic medications, such as steroids, can result in health problems. Working with your pet’s veterinarian to diagnose the underlying cause may prevent the pruritus from returning or reduce the need for medications.

How will my veterinarian diagnose the cause of my pet’s pruritus?

The information you provide about your pet’s pruritus and other medical history can sometimes help your veterinarian determine the cause of your pet’s itching.

When the pruritus started
As some skin problems are more common in younger pets while others are more common in older pets, it can be helpful to know when the itching started. For allergies, it can be helpful to know during which seasons a pet has pruritus because different plants pollinate during different seasons.

What medications have been tried: A lack of response to some medications can help your pet’s veterinarian narrow down the possible causes. Additionally, some medications can actually cause itching.

What other health problems there are
Sometimes skin conditions develop secondary to another health problem. Your veterinarian will ask questions about other symptoms that could point to a specific cause of pruritus. For example, pets with food allergies may defecate frequently or have soft stools.

During the office visit, your veterinarian will examine your pet as this can sometimes help determine the cause.

Location of skin lesions
Some pruritic skin conditions cause skin lesions more commonly in one body region than another.

Type of skin lesions
Although most pruritic skin conditions look the same to pet owners, there are actually many types of skin lesions and some skin lesions occur more commonly with specific skin conditions. However, if the pruritus has become chronic, many pruritic skin conditions look similar to each other. Your veterinarian may need to run some tests to help determine the cause of the pruritus.

What tests are used to diagnose the cause of my pet’s pruritus?

Below is a list of some common tests for diagnosing the cause. Your veterinarian will select tests based on your pet’s medical history and examination findings.

Skin scrapings
To look for skin parasites, a scalpel blade is used to gently but firmly scrape the skin layers to collect cells and any skin mites. The sample is then examined under the microscope.

Skin cytology
To look for bacteria and yeast organisms, samples of skin cells and debris are collected and placed on a glass slide for examination under the microscope. This test can also help determine what types of cells are in the skin.

Parasite therapy trial
For some parasites, the only way to determine if they are the cause of the itching is to treat for the parasites. A decrease in pruritus after the parasite therapy would be consistent with the parasite causing the pruritus.

Ringworm culture
To determine if a dog or cat’s skin is infected with ringworm (a dermatophyte), samples of hair and scale are collected and placed on a fungal culture plate. If a dermatophyte grows, then the dog or cat is diagnosed with ringworm.

Food trial
To diagnose food allergies, a prescription or home-cooked diet is fed for several weeks with no other foods or treats. Unfortunately, there is no reliable skin or blood test in dogs and cats to diagnose food allergies.

Allergy testing
Skin or blood allergy testing is used in dogs and cats that have had other causes of pruritus ruled out through other tests. It is used primarily to select allergens for a type of allergy treatment called allergen-specific immunotherapy. There are no reliable hair or salivary tests to diagnose allergies.

Skin biopsy
A sample of skin can obtained through minor skin surgery. Skin biopsy is especially helpful for diagnosing some less common causes of pruritus such as skin cancer. However, skin biopsy cannot be used as an allergy test and cannot diagnose the cause of a pet’s allergies.