Why Is My Dog Losing Her Hair in Clumps?

Updated July 19, 2017

Whenever a dog owner has concerns about her dog's health, she should see a veterinarian. If a dog is losing hair or shedding more than it does normally, there could be a number of reasons why. Hair loss in dogs is not always a sign of a serious problem, but it is best to let your veterinarian decide if your dog needs treatment.

Insects and Parasites

A typical culprit in canine skin irritation and resulting hair loss is a flea problem. Fleas can irritate a dog's fur, often causing the dog to itch and scratch excessively. If you are using flea collars or flea control medicine, be sure you are using it correctly. Over-bathing or incorrect dosages can prolong a dog's skin problem. Mites, mosquitoes and worms also can irritate a dog's skin.


Poor nutrition can be the cause of a dog's hair loss. Dogs missing nutrients in their diet may have rough, unhealthy-looking coats and may also experience a large amount of hair loss. Dogs also may have allergic reactions to the foods they eat. The irritation caused by the allergens in the food may cause a dog to scratch excessively.

Hormonal Imbalance

As dogs get older, they are more likely to be affected by hormone imbalances. For instance, the thyroid gland is the gland responsible for a dog's energy level and rate of food digestion. When the thyroid is not working as it should, a dog's coat could suffer hair loss. Other hormonal diseases, such as Cushing's disease could result in hair loss in dogs.


Like their human owners, dogs can experience emotional turmoil. Dogs that have moved recently, miss someone or find themselves in other unfamiliar situations may experience stress. Lack of exercise also can be a factor. It is important to note that stress and hair loss may also be a symptom of an underlying, serious illness, so it is important to let your veterinarian know if your dog's behaviour seems unusual.

Reaction to Drugs and Medical Treatments

Dog skin can be irritated by both medicine and medical treatment. Dogs injected with antibiotics may have strong reactions to the injections, causing inflammation of the skin. Aside from reactions to medication, dogs being treated for chronic illnesses may lose hair. For example, like humans, dogs undergoing chemotherapy often lose hair.

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About the Author

Ray Ray Montoya is the son of two English majors and has himself followed suit. He received his bachelor's degree from Northern Michigan University in 2006 and two years later received his M.A. from the same institution. He currently teaches at a community college in Michigan and writes for various websites.