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What Causes Hair Loss in Cats and Dogs?

By March 7, 2019Pet Care, Pet Health
What Causes Hair Loss in Cats and Dogs?

Pet hair loss can be very upsetting to pet owners – that thick fluffy coat you love to stroke may begin to have bald patches (alopecia) or areas of thinning hair. Pet hair loss may indicate an underlying illness or problem. Our furry friends are experts at hiding symptoms of disease and the first sign of trouble we may notice is hair falling out. Here are the leading causes of hair loss in dogs and cats.

Skin Parasites and Infections

Fleas, mites, and lice cause itching that drives a pet crazy. The pet scratches or bites, and the hair is broken or chewed off. Then the moist, chewed skin becomes the perfect environment for skin infections. These infections also cause itching which results in even more hair being chewed off.


With pets, allergies tend to affect the skin and ears. Allergies cause itchy skin and then pets scratch or chew out their hair. As well as food, pets can be allergic to the following:

  • Inhalants – pollen, cigarette smoke, perfumes (especially those in cat litter).
  • Skin contacts – e.g., chemically treated carpets, lawns, or decks.

Poor Nutrition

Pet hair requires a continual supply of essential nutrients, if it is to remain anchored in the hair follicles. Therefore, a poor diet can trigger pet hair loss. And, some northern dog breeds, such as Siberian Huskies, are genetically unable to absorb zinc from their food.

Abnormal Organ Function

Various body organs regulate nutrients in the blood. Therefore, diseases and drugs affecting these organs directly influence pet hair loss. For example:

  • Inflammatory bowel disease, cancer, and chemotherapy drugs can cause dull, thinning hair.
  • Kidney failure produces a bedraggled, dull coat and skin that may emit a strong urine smell.
  • Liver failure causes orange-yellow skin (jaundice), and weak, flaky nails.

Inadequate Blood Flow

Hair is a living element anchored in the hair follicle and nourished by blood. When the blood doesn’t circulate well, hair doesn’t grow well. Pets with chronic anemia, low blood pressure, and weak hearts may have cool skin and dull thinning coats.

Excessive or Deficient Hormone Levels

Many hormones influence hair growth, including estrogen, testosterone, melatonin, growth hormone, thyroxin, and cortisol. Abnormal levels of these hormones cause hair to be too thin or too thick.

Pet Medications

Certain medications can lead to pet hair loss. For example:

  • High doses or long-term use of steroids.
  • Topically applied flea medications can cause hair loss at the application area.
  • Injected vaccines may result in hair loss at the injection site and further widespread hair loss later.

Behavioral Problems

Dogs with high levels of separation anxiety may lick patches of hair off their legs (acral lick dermatitis). This licking may break down the skin and lead to skin infections. Cats can “barber” themselves until bald spots spread over the abdomen and thighs.

Pet Hair Loss Should be Evaluated

All pets are susceptible to hair loss, but certain breeds have their own particular problems. Your vet will determine the underlying cause of the hair loss and prescribe appropriate treatment. Pet hair loss does not constitute an emergency, but if your pet is ever in an emergency situation and you live in the Columbia, South Carolina area, bring them to CVETS for the most up-to-date emergency treatment.