Understanding your pet's Itchiness

Understanding Your Pet’s Itchiness

Pruritus is the itch sensation that leads to the desire to scratch, rub or lick in an effort to relieve the sensation.  The most common causes of pruritus in dogs and cats are parasites, allergies, and infections.

Parasites can cause pruritus in several ways.  Many cause trauma to the skin through biting, burrowing, or stinging, but pets can have allergies to their saliva, venom or even contact with their body parts.  Fleas are the most common cause of skin allergy in pets worldwide. Insects such as flies, mosquitoes, bees and even ants as well as other parasites like ticks, lice and mites can also cause skin disease and pruritus however.  Mites such as Cheyletiella (walking dandruff) and Sarcoptes (scabies) live under various layers of the skin and are often acquired from foxes or other wildlife. They are transmissible between animals and can also affect humans.  Luckily many parasites, not just fleas, are easily managed through use of topical parasiticides (Revolution, Frontline, Advantage, etc), which is why these products are so important in the management of pruritus.

In companion animals, there are three main categories of allergies: insect allergies, food allergies, and environmental allergies.  Insect allergies as described above, are usually a hypersensitivity reaction to the saliva of the insect, which results in inflammation of the skin. This leads to intense scratching, licking and chewing.  Flea saliva hypersensitivity is the most common insect allergy observed in cats and dogs.

Environmental allergies and food allergies are often lumped together under the umbrella of atopic dermatitis.  Technically speaking, atopic dermatitis is a genetically predisposed inflammatory skin disease caused by environmental allergies, but food allergies can trigger flare ups with the same symptoms.  Environmental allergies have often been called inhalant allergies, though this is somewhat misleading since contact of the allergen by the skin is the actual method of exposure. House dust mites are the most common environmental allergen in dogs and cats, but allergies to grasses, trees, weeds, and molds are also frequent.  Food allergies can develop at any age, though up to half of pets diagnosed are 1 year of age or less. The most common food allergens are beef, chicken, wheat, corn, eggs, and dairy, but a pet can become allergic to anything they eat. About 10-15% of dogs with food allergies will have gastrointestinal symptoms (e.g. vomiting, diarrhea, gas) as well.  

Atopic dermatitis, whether from food or environmental allergies, leads to inflammation that causes a defect in the structure and function of the skin.  The allergy itself causes itchiness, but the skin defect can lead to secondary infections with bacteria, yeast, or both. Allergic skin is itchy, but allergic skin with infection is worse.  Because of this, a major part of treating atopic dermatitis in pets is treating and controlling the infections that result with topical or oral antibiotics and antifungal agents.

Having an itchy pet can be incredibly frustrating for both you and your pet.  It is important to understand the causes as some are curable and others, like allergies, will require life-long management.  Treatment often involves corticosteroids (Medrol, prednisone, Depo-Medrol, Temaril P), allergy specific immunotherapy (allergy shots or sublingual drops), and/or allergen avoidance.  Luckily there are new therapies, Apoquel and Cytopoint, that help control pruritus by blocking the substances in the body directly responsible for the itch sensation. These have shown great effect in dogs and Apoquel has begun to be used in cats as well.