Hair Loss and Scratching in Dogs

Causes, Treatment, and Prevention

Dog Scratching

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Hair loss and scratching are two of the most common reasons dogs visit veterinarians, and there are several causes for these distressing symptoms including parasites and infections. To diagnose and treat your dog for its irritating skin condition, your veterinarian will become a medical detective, performing thorough examinations and laboratory tests to track down the source of your pup's displeasure.

What Are Hair Loss and Scratching?

Hair loss (technically called alopecia) and scratching are symptoms of irritation affecting a dog's skin. While they indicate itching and damaged skin, they do not point to a specific condition. Instead, they can occur as a result of many possible dermatological afflictions.

Symptoms of Hair Loss and Scratching in Dogs

If your dog's skin is irritated, no matter the cause, it may experience the following symptoms:


  • Scratching or chewing skin
  • Patches of bare skin
  • Clumps of hair lying around the house
  • Red, inflamed, or bleeding skin

Patches of missing hair and excessive scratching are symptoms that must be addressed by a veterinarian to determine a cause and treat it effectively.

Causes of Hair Loss and Scratching

The causes of a dog's hair loss and scratching can range from simple external irritation to internal organ dysfunction. Possibilities include:

  • Parasites (such as fleas, ticks, mange mites, or lice)
  • Allergies to food, pollen, or other environmental irritants
  • Bacterial or fungal infections
  • Liver disease (irritating bile salts accumulate under the skin)
  • Thyroid dysfunction

Diagnosing Hair Loss and Scratching in Dogs

Your veterinarian will begin the search for the cause of your dog's hair loss by asking you some basic questions. Prepare to answer these questions:

  • When did your dog start to lose hair?
  • Is your dog itchy?
  • Has your dog suffered from similar problems in the past? If so, when?
  • Is your dog currently taking any medications? Herbal supplements?
  • What is your dog eating at meals and in the environment?
  • Have you noticed symptoms other than scratching or hair loss?
  • Are there other pets in your home and, if so, are they experiencing similar problems?
  • Are family members noticing any abnormal skin lesions?

Physical Examination

Your dog will have a physical examination from head to toe, looking for evidence of parasites, skin lesions (such as red spots, scabs, and sores), and overall health. The examination will include the eyes, ears, teeth, and other body parts as well. This is because skin disease can sometimes be a manifestation of disease in an internal organ system or other parts of the body.

The results from the history and physical examination will help your veterinarian determine which diseases are most likely causing hair loss and scratching. The results will also help in determining which diagnostic tests should be performed.

Specific Tests for Skin Disease

If your dog is suffering from skin disease and has been losing hair or scratching, there are several tests your veterinarian may recommend performing. These include:

  • Skin scrapings to look for evidence of the mites that cause mange
  • Skin cytology looking for evidence of yeast and bacterial infections in the skin
  • Fungal cultures that check for ringworm (not a worm) and other fungal infections
  • Skin biopsies if skin cancer or other serious skin disease is suspected

Diagnosing Systemic Conditions

In some cases, if your veterinarian suspects that a more systemic (whole-body) disease is causing your dog's skin disease, a blood screen may be recommended. A blood screen usually consists of a complete blood count (CBC) and a chemistry profile.

The complete blood count looks closely at the red and white blood cells in a blood sample. The blood chemistry profile allows the evaluation of kidney function, liver enzymes, protein levels, and electrolyte levels.

In dogs with skin disease, blood screening may also include tests that evaluate the thyroid function, including total T4, free T4, and/or thyroid-stimulating hormone (TSH).

Diagnosing Skin Disease With Flea Control

If your dog is scratching and losing hair, one of the first things your veterinarian will likely recommend is a reliable form of flea prevention if you are not already using flea control. This is because fleas can be notoriously difficult to find on dogs, even when fleas are the main trigger for the condition.

If fleas are not the cause, controlling them is still important, as any fleas are likely to make an original skin problem much worse.

Diagnosing Skin Disease Caused by Food Allergy

After fleas have been treated and ruled out as the cause of the itching, your veterinarian may recommend doing a food trial. A food trial involves feeding your dog a special diet for two months to bring your dog's immune system back to a non-reactive baseline.

This special diet is called a novel protein diet or a hydrolyzed (chemically digested) diet; it is devoid of all protein and carbohydrate ingredients that are the most common triggers of food allergy in dogs. Normal protein triggers are beef, milk products, chicken, and eggs, while common carbohydrate triggers are wheat, corn, and soy.

Once the dog's immune system has calmed down, these ingredients can be tried one by one to see if they induce skin reaction. If so, itching symptoms will appear within about three days. Most food-allergic dogs will show sensitivity to more than one kind of protein or carbohydrate.

Allergy Testing and Immunotherapy (Hyposensitization)

If other causes of hair loss and scratching have been ruled out and if your veterinarian is relatively certain that your dog is suffering from atopy (an immune system that is sensitive to something in your pet's environment), then allergy testing may be recommended.

Allergy testing can determine which substances your dog is allergic to. The treatment for acquired allergy is immunotherapy, also called hyposensitization. This involves injecting a solution of the allergen (the substance causing the allergy) into your pet over some time in an attempt to train your pet's body to not respond abnormally to the allergen.

Treatment and Prevention

The treatment of hair loss and scratching in dogs depends on the cause and must be targeted to the specific organism or condition causing the skin inflammation.

Prevention of most skin diseases involves a nutritious diet, plenty of exercise, regular de-worming and vaccinations, and preventative medication to ward off fleas and ticks.

Liver disease and thyroid conditions in dogs are not necessarily preventable because they can occur as a natural part of the aging process, and some dog breeds are more prone to these conditions. But the above measures will help your dog live as healthily as possible and cope better with these conditions if they do arise.

Prognosis for Dogs with Hair Loss and Scratching

Again, the prognosis for a dog afflicted with hair loss and scratching depends on the cause of the symptoms. Most parasitic, bacterial, and fungal infections can be treated within a couple of months, and dogs resume their normal lives. Hypothyroidism can be managed with medication; liver disease may require more intensive treatment and carries the most guarded prognosis of the possible causes.