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3 Most Common Causes of Itching

3 Most Common Causes of Itching
November 1, 2020

Coping with an itcy pet can be extremely frustrating experience for you and test the limits of your relationship with your pet. Persistent scratching and chewing by your pet can also result in self-induced open sores and wounds. The following information is a general explanation of the most common causes of itching in animals: allergies, secondary skin infections, and ectoparasites (skin mites and fleas).


An allergy is when exposure to a harmless substance known as an allergen induces your pet’s immune system to overreact. This response is similar to what humans experience when they suffer from allergies, but in animals, clinical signs typically present as redness and itching, recurring skin or ear infections and hair loss instead of runny noses, watery eyes, sneezing or asthma. This is sometimes called eczema or atopic dermatitis. Allergies are usually cumulative and as such can be caused by a single source or due to an accumulation from multiple sources.

What are the major types
of allergies?

#1 FLEA ALLERGY. This is the most common in dogs and cats and can affect them starting at any age. For the flea allergic patient, quick, effective and monthly flea control is essential to remain symptom-free. Many clients feel like they never see fleas on their pets or themselves (aka “flea-nial”), but that doesn’t mean that they are not there. A flea allergy comes from the flea’s saliva and it only takes a few bites to cause a flare-up. Itchy patients often scratch, chew or groom themselves so much that the adult fleas are removed, making them hard to find. Flea allergy patients commonly have hair loss, crusting and redness on their lower backs, around their tails and down the backs of their thighs.

#2 FOOD ALLERGY. Some patients develop specific sensitivities to components in their food or treats that they eat. Food allergens are usually to a protein or carbohydrate such as beef, pork, chicken, corn, wheat, gluten, soy, egg or dairy. Diagnosis of a food allergy is done by introducing a food that is hypo-allergenic for a period of at least 10-12 weeks. Anything given to your pet orally must be checked for allergens including dietary supplements, heartworm pills and most importantly treats. Food allergies typically appear in animals less than a year of age (especially if 6 months or younger) or older than 5 years. They commonly have itching around their bottoms, itchy ears and sometimes gastrointestinal symptoms such as vomiting, diarrhea or excessive production of stool.

When choosing foods, be sure to read the small print on the ingredients list. If a food says Lamb and Rice or Chicken and Rice, it may still contain beef, wheat or dairy as minor ingredients. Beef may be listed as meat by-products, animal by-products, beef tallow or animal fat. Dairy products may be listed as milk, casein or whey. Wheat may also be listed as wheat or gluten. Please by sure to read the labels on any foods, treats, flavored supplements or medications you give your pet.

#3 ATOPIC DERMATITIS (Atopy). This is an inherited predisposition to develop skin problems from exposure to commonplace and otherwise harmless things such as pollens, grasses, trees, mold spores and dust mites. Definitive diagnosis of atopy is made based on results of intradermal skin or in-vitro blood testing. Evaluation of the results of these tests helps us compile a list of allergens for a tailored “vaccine” (allergy shot) to decrease your pet’s sensitivity. Atopic dermatitis cannot be cured, and treatment for it should be directed toward each individual pet. Our overall goal is to reduce flare-ups, prevent or treat secondary complications and above all preserve quality of life for your pet. Atopic animals typically begin to show clinical signs anywhere between 6 months and 3 years of age. The most common clinical signs of atopy are itchiness, licking or chewing on the feet, recurrent ear infections, mucous-like discharge from the eyes or runny eyes-particularly in the morning or just after going outdoors.

Secondary Skin Infections

85% of itchy animals have secondary skin and/or ear infections due to yeast, bacteria or fungal overgrowth and allergies are often the underlying cause. Treatment with medicated shampoos, antibiotics and anti-yeast medications may be necessary depending on the severity. In some cases where infections are chronic, special tests for metabolic and endocrine diseases such as hypothyroidism, diabetes and Cushing’s disease may be performed since these can suppress your pet’s immune system. Biopsies or skin cultures may be warranted too.


Ecotoparasites are organisms that live in or on the skin, but not within the body. Other than fleas, the next most common ectoparasites that cause itching are mites. Some mites, such as sarcoptic mange, burrow into the skin and cause intense itching, while demodex mites overproliferate in the hair follicles and cause secondary bacterial infections and inflammation. Neither of these mites is visible to the naked eye.

Sarcoptic mange is intensely itchy and typically shows up on the ear margins, elbows, hocks, chest and belly. Diagnosis is made with a skin scrape and microscopic evaluation. Unfortunately in many dogs, it is hard to capture these mites and diagnosis is made by response to treatment. Sarcoptic mange is contagious to your other pets and you as well although you are not a preferred host and infections are self-limiting. Infected animals undergoing treatment can remain contagious for two to four weeks. During this time, it is a good idea to wash any bedding in the home as well as any pet clothing, collars or harnesses or pet toys.

Demodectic mange (demodicosis) is usually not intensely itchy and in some cases not itchy at all. It can present itself in a localized area or more generalized. Symptoms include hair loss and skin reddening. Affected areas may be scabby or crusty and skin infections due to damage by the mite are common. Demodicosis can occur at any age but is most commonly seen in young, old, and debilitated patients or those with compromised immune systems. Demodectic mange is typically not contagious to you or other pets in the environment.

What can I do now to help stop the itch?

1. Be prepared to discuss with your veterinarian when your pet’s itchiness started, what clinical signs you are seeing (redness, pustules, discoloration of skin, etc.), how often they occur, what food and treats they are eating and your pet’s environment.
2. Check food and treat labels as directed above for common allergens.
3. Apply flea and tick medication monthly all-year-around.
4. Perform an anti-histamine trial for 14 days.
5. Give Omega-3 fatty acids to supplement the skin and coat and to act as a natural anti-inflammatory. Fish or flax seed oil can be used. The general dose is 200 mg/10 lbs daily for dogs and cats.
6. Bathe your itchy animal weekly with a conditioning shampoo containing colloidal oatmeal. In some cases medicated prescription shampoos may be needed instead.
7. Avoid going outdoors or on walks with your pet during times of the day when pollen counts are high.
8. Wipe paws and faces with a damp paper-towel or wash cloth after being outdoors.
9. Wash bedding and toys at least weekly, change air filters in your home monthly, dust and vacuum frequently.

The information in this brochure is a compiliation of information from the following sources.
Dermatology: Itching and Allergies in Dogs, VIN Library, Dr. Carol Foil, DVM, MS Diplomate A.C.V.D.
Dermatology: Itching and Allergies in Cats, VIN Library, Dr. Carol Foil, DVM, MS Diplomate A.C.V.D.
Dermatology: Demodicosis, VIN Library, Dr. Carol Foil, DVM, MS Diplomate A.C.V.D. Dermatology: Sarcoptic Mange, VIN Library, Dr. Carol Foil, DVM, MS Diplomate A.C.V.D.
Small Animal Dermatology Secrets, Karen. L Campbell, DVM, MS, DADVIM, DACVD, 2004, Hanley and Belfus, Philadelphia, PA
Hartfield Animal Hospital Food and Allergy Handout, Steve Skinner, DVM