Why Do Dogs Shed? The Reasons Dogs Lose Their Hair Throughout the Year

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The age old question that all pet parents ask themselves as they vacuum up their dog's hair: Why do dogs shed? Well don't feel bad, scientists have been trying to figure it out for years. Here is a list of reasons why dogs might shed so much.

The question of why dogs shed puzzles even scientists -- why does their fur grow in and fall out in an endless cycle? Current science has broken down shedding into three phases: hair growth (anagen phase), a brief period of neither growth nor shedding (catogen phase), and, finally, the shedding period (telogen phase).

In some breeds, this cycle can take up to a year, whereas in other breeds, it can happen in as few as 30 days. The breeds whose cycles are longer shed less, and those whose cycles are shorter shed more. Poodles and some Terriers, for example, shed less than many other breeds due to their long shedding cycles. Labs and Huskies, on the other hand, have a shorter cycle of growth, making them heavy shedders (as any Lab owner can attest).


There are a variety of health problems for which shedding is an indicator. A healthy dog will generally shed less than a sick dog.


Strange hair loss or excessive shedding can point to:

  • Hormonal issues
  • Allergies
  • Fevers
  • Parasites
  • Chemical imbalances
  • Dietary deficiencies
  • Skin conditions
  • Stress
  • Spinal issues

Generally speaking, excessive shedding most often points to allergies or hormonal issues.


Hair loss can indicate that your dog is having an allergic reaction to something in their environment, an ingredient in their food, a new drug, or even the weather.

Just as with people, determining the source of an allergy can be tricky. Elimination is the favored method of deduction.


Excessive shedding can be a sign of hormone imbalance. An underactive thyroid, for example, will often result in dry, brittle hair that breaks and falls off. This condition can be resolved with medication.

Other hormonal issues involving the over- or under-production of testosterone, estrogen, and progesterone can cause a dog to shed more than usual.

Lactation & Pregnancy

Hormones are never in more flux than when a dog is pregnant or nursing. A nursing mother, low on energy and certain vitamins and minerals, will shed more than she typically does. Certain supplements can help, but discuss options with your vet, as some supplements can do more harm than good. Just know that some hair loss during this time is normal.


Some dog breeds will shed in response to the change of seasons -- usually once a year in spring, but sometimes in the fall as well -- by losing a whole bunch of fur all at once.

In the spring sunlight, warmer weather and longer days trigger a dog’s follicles to release the winter coat. Most dogs, even hardy working breeds, are now companion animals who live inside with their humans. For this reason, an extreme seasonal shedding response is less common than it used to be. Now, most dogs shed year round.

More on Dog Shedding

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General Allergies Skin Allergies Alopecia (Hair Loss)

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