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Why is My Dog Losing Hair?

a big brown and tan dog laying in the green grass scratching his face

When your dog has a shiny coat of hair, this is a sign of good skin health. But what does it mean if your dog has a dry or brittle coat? What happens if your dog starts losing hair? These are a few examples of clinical signs that can be associated with poor nutrition or illness.

Warning signs

Before hair loss happens, some dogs may appear to be itchy. You might notice that your dog is chewing, licking, biting, or scratching himself. His skin may appear dry or maybe excessively pink or red. His hair coat may appear dry and brittle, and he may have lots of flakes or crusted lesions. After a little while, he may begin to lose hair. It can come off in a round, circular patches or in large clumps. The hair can fall off in one area or in multiple places, and sometimes the location of the hair loss can give us clues as to what the cause might be.

Causes of hair loss in dogs

a close up image of a dogs skin due to hair loss.

Hair loss that is associated with itchy skin can imply numerous causes. Allergies are one of the most common causes and are typically broken down into three categories. Dogs can be allergic to flea bites and tend to lose the hair over their lower back and hips when they have an allergic flare-up. Dogs with environmental allergies such as pollen, grass, weeds, trees, and dust mites usually lose hair on their limbs and their bellies. Dogs with food allergies can be more difficult to differentiate because they lose hair almost everywhere!

Itchy dogs tend to scratch or chew on themselves, and this can bring about secondary bacterial infections that result in further hair loss. Fungal infections are also possible due to the presence of small amounts of yeast on healthy skin. When skin becomes dry and inflamed, there is an increased risk for bacterial infections, and when there is excess moisture from licking, yeast can cause infections, too. Skin mites can also cause hair loss, although sometimes mites likeDemodex may not cause itchiness, so it is important to have your dog tested when you see hair loss.

Another type of fungal infection, ringworm, is caused by a fungus that is transmissible by contact. It can come from other animals or can come from dirt and soil. This fungus can cause ring-like lesions on the skin which results in a round-shaped area of hair loss. Ringworm is zoonotic which means that humans can also develop it from contact, so it is important to make sure to address itchy skin with your veterinarian (and sometimes with your own physician) right away!

Hormonal imbalances, aka endocrinopathies, can also cause hair loss. Hypothyroidism is when a dog’s thyroid gland does not produce sufficient amounts of thyroid hormone. As a result, dogs can become overweight and will drink and urinate a lot more than normal. Their hair coats become brittle and they can lose hair more easily, making them more susceptible to skin infections and itching. Another disorder known as Cushing’s disease is when a dog’s adrenal glands produce too much cortisol. This ends up causing many problems such as a potbelly, darkened skin, itching and hair loss, and excessive appetite, thirst, and urination. It affects middle-aged to senior dogs, and treatment depends on the type of Cushing’s disease present. It can be easy to attribute hair loss to allergies alone, but if your dog is drinking or urinating a lot, he may need testing for some of these illnesses.

Not all causes of hair loss require treatment. Pressure sores, which are skin-level ulcers, are a lot like calluses and develop in locations that contact hard surfaces consistently. The elbow is one of the most common places. Pressure sores become a health concern when they become dry, cracked, and start to bleed. If your dog starts to develop them, consider new bedding to help prevent them from worsening.

Prevent or treat hair loss in dogs

The ultimate treatment for hair loss depends on the underlying cause. Dogs with skin infections often require topical and sometimes systemic antibiotics or antifungals. Flea prevention year-round is important in dogs with flea allergies. Food allergic dogs need to undergo a food elimination trial for six to eight weeks with either a novel protein diet or a hydrolyzed protein diet. Dogs with food allergies and contact allergies benefit from the use of anti-itch shampoos, antihistamines, and novel anti-itch medications like Apoquel and Cytopoint. Severe allergies may require short-term use of a steroid medication, which can cause increased thirst and urination.

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Allergy testing is ideal because it can be used to find the exact environmental allergens responsible and can be used to help develop an allergy vaccine used to “reboot” your dog’s immune system. With this kind of immunotherapy, your dog may be less likely to have a severe allergic reaction if he comes into contact with his known allergens again. There is ultimately no cure for allergies that will be 100% effective, so it is important to find what works and stick to it!

Routine blood and urine testing can help screen for endocrinopathies like hypothyroidism and Cushing’s disease. If your dog has hypothyroidism, then he will need to take a thyroid medication twice a day for life. If your dog has Cushing’s disease, he will need additional testing to determine which type he has – either pituitary-dependent Cushing’s or an adrenal gland tumor. The former is treated with an oral medication once or twice a day while the latter needs to be treated surgically. A well-balanced diet packed with omega-3s and vitamin E can help keep your dog’s coat shiny and healthy. Supplements like coconut oil and CBD oil can help with mild itching and inflammation.

Hair loss can appear mild but can indicate a major underlying issue. Allergies are one of the most common causes but hormonal disorders like hypothyroidism and Cushing’s disease are also possible. Routine blood and urine testing can help rule out some of these disorders, and your veterinarian will be the best source of information on products, tests, and treatments to help your dog. If your dog is itchy or losing hair, contact your veterinarian right away!

Meet The Author 

Dr. Erica Irish DVM


Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.

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