Pet Articles

Itchy Dogs – Itchy Cats

It’s not difficult to spot the owners of an itchy pet. They’re the ones that look as though they haven’t slept for days, having been kept up night after night by their pet’s incessant scratching. They’re also the ones with a frustrated look on their faces, an expression that has been etched in place after countless attempts to get the itchiness problem under control. For the owners of dogs or cats suffering from chronic itchiness, these descriptors are likely all too familiar. However, what may not be so familiar to these people is the idea that itchiness is a multifactorial problem, and that understanding this complex interplay of factors is the first step to arriving at a workable therapeutic plan.

Before we delve further into this topic, it is important to take a moment to clarify what is meant by an “itchy pet.” While the average dog or cat may occasionally scratch itself in response to touching, insects, or even for no easily identifiable reason at all, itchy pets are those that are near constantly consumed in their discomfort.

The fur on their paws may be discoloured a bronzish hue from saliva staining, indicative of chronic paw chewing to alleviate the itch.

They may shake their heads countless times per hour, even developing large blood blisters (or “hematomas”) on the ear flaps as they repeatedly slap against the side of the head. Itchy pets may rub their itchy faces along the grass of the front lawn or along carpeted surfaces to gain relief. Worst of all, many will scratch themselves so rigorously with their claws or teeth, or lick at themselves so continuously, that they break the skin and create secondary abrasions that themselves become infected. Often times, hair is missing at these sites as well, due to this self-trauma.

Assessing a pet’s degree of itchiness is obviously highly subjective and relies on owners’ careful observations over a period of time and during many different times of day. In general, itchiness (or “pruritus,” as your veterinarian may call it) is considered to be problematic when it becomes extremely noticeable (that is, extremely frequent or intense), disruptive to you or your pet’s quality of life, or appears to be causing obvious discomfort to your pet. For example, for owners whose pets share their beds, having a pet spend night after night gnawing at itself, unable to settle down comfortably, might be considered cause for concern. A pet that has deep gashes, sores, and hair loss all over its face from its relentless scratching may also be a good candidate for the title of “itchy pet.”

Now that we have a clearer definition of the traits encapsulated by the word “itchy” – versus the perfectly normal, occasional itching and scratching behaviour of the average pet – we can begin to explore their causes.


‘Ectoparasites’ refer to that group of parasites that affect the outside surfaces of animals (in contrast to endoparasites, which colonize their internal parts, such as the gastrointestinal tract).

Fleas are a common culprit in dogs and cats that are variably itchy, particularly along the lower back, rump, and inner thighs. Fleas themselves cause only a mild itchiness, but in susceptible individuals, flea bites can trigger highly pruritic hypersensitivity (allergic) reactions which may lead to secondary abrasions, hair loss, and infections due to the intense irritation. Fleas are easy to diagnose, since the fleas themselves and their feces (known as “flea dirt”) are visible to the naked eye. It should be noted that although the most common types of fleas prefer to feast on cats, both dogs and people are frequent flea targets. Today, monthly flea preventatives, many of which are combined with heartworm preventatives, constitute the treatment of choice, relegating products like flea collars and flea powders to the land of the near-obsolete. For more information on controlling an existing flea problem or preventing them in the future, your veterinarian is your best resource.

Lice are another subset of itch-causing ectoparasites. Lice may be transmitted directly from animal to animal or spread indirectly via objects such as grooming tools. They come in biting and sucking varieties, the former being a much more significant cause of skin irritation. Like fleas, the diagnosis of lice is not difficult; finding lice or their eggs (“nits”) throughout the coat and skin is usually sufficient. Many of the monthly flea preventatives, such as ivermectin- or selamectin-based products, have efficacy against lice as well.

Mites represent another common cause of pruritic pets. The Cheyletiella variety (known affectionately by veterinarians as “Walking Dandruff”) is usually found along the backs of affected animals, and is highly contagious, including to people. Scotch tape strips placed along dorsum (back) for examination under the microscope are the primary means of diagnosis.

Demodex mites are normal inhabitants of the skin that only cause problems when they are allowed for some reason to proliferate unchecked by the host immune system. This may be due to either an immaturity of the immune system (as in the case of ‘Juvenile Demodicosis’) or an underlying immunosuppressive condition, such as that occurring secondary to serious illnesses like cancer or to recent treatment with steroids (‘Adult-Onset Demodicosis’). Because of the genetic basis of immune system functioning, juvenile cases should not be used for breeding. Young animals may self-cure as their immune systems mature, keeping Demodex numbers under control. Once diagnosed and any possible underlying disease is worked up, adults are treated with daily oral ivermectin or milbemycin therapy.

Sarcoptes mites are suspected in any animal with sudden onset, intense itching, particularly at the elbows, knees, and ears. Unlike Demodex, they are contagious, so all in-contact animals must be treated, preferably with selamectin-based products. Talk to your veterinarian about prevention and treatment protocols.


Hypersensitivity, or “allergy,” refers to the over-reaction of an individual’s immune system to particular items with which they are in contact. Pets may be hypersensitive to allergens in their food or in their environment, such as pollen, grasses, or dust. It is important to remember that the majority of pets with food hypersensitivity have been on the offending food for months or years, and that it can occur at any age. Environmental hypersensitivity (also known as “atopy”) may follow a seasonal pattern (that is, every spring for pollen allergies) or be year-round if the allergen is found indoors. The importance of chasing down a pet’s hypersensitivity is that it is a very common underlying cause of low-grade itchiness that when combined with another cause of itch, creates an additive effect. Diagnosis of food allergy is made with strict exclusion diet trials; atopy is best diagnosed with intradermal skin testing in the fall. Talk with your vet if you suspect that an underlying hypersensitivity is causing or contributing to your pet’s itching.

Bacteria & Yeast

Infections of the skin by bacteria and yeast are usually secondary to other factors which promote their colonization. Ectoparasites, hypersensitivity, immunosuppression, and self-trauma are just some of the possible initiating causes that change the skin’s microenvironment in favour of bacterial of yeast overgrowth. Just as in people, bacterial skin infections appear red, pimply or pus-filled. Yeast infections have a distinctive, unpleasant odour and usually occur between the toes and on the face. Diagnosis is made by examining swabs from affected areas under the microscope. Treatment is aimed at eliminating the secondary bacterial or yeast involvement with antibiotics or shampoo therapy, as well as identifying and controlling the primary, inciting cause, such as mites or food allergy.

The Bottom Line

While dealing with an itchy pet may seem like an exercise in frustration, it is by no means an exercise in futility! Understanding the different potential causes of itchiness helps to underscore the importance of distinguishing between them as a first step to treating the underlying cause. That message should hopefully bring relief to both you and your pet.

By Rebecca Greenstein – writer

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