Hair Loss (Alopecia) in Dogs: Why Is My Dog Losing Hair?
Depending on your dog’s breed, you can find yourself knee-deep in hair twice a year. I can tell you that even our Rotties, who but no stretch of the imagination, are fluffy dogs, can drop an enormous amount of undercoat. You would never expect it–they don’t look like they’re wearing much. But when Jasmine was shaved for her surgeries, it was visible she had about an inch of tightly packed undercoat.
That is normal shedding and not what we’re talking about.
You and your family members, too, put away your winter coat when spring comes. And depending on how tight of a household you run, you might also find garments all over the floors.

The difference between shedding and hair loss isn’t where you find the hair but where you don’t find it–on your dog.
Finding bald spots on your dog means there is a problem. Your dog can have just bald patches or lose hair all over.
There were three reasons I have found bald patches on my dogs.
Jasmine was hypothyroid and prone to skin infections. We kept things under control reasonably well, but she had a hot spot twice and folliculitis (an infection of hair follicles) twice. She lost the most hair with that one, and for a while, it looked like it would never grow back. The chunks of coat that came off her still had bits of skin attached to them.
JD had a bald spot which we thought was a result of the game of chicken he played with a tree. Unfortunately, the tree didn’t blink, and JD ended up with a boo-boo on his nose. Even though it looked healed, the area remained hairless. It turned out he got a ringworm infection.
The most mysterious hair loss was Jasmine’s dime-sized spot on her flank. It wasn’t ringworm. It wasn’t anything else, either. Out of all things, her veterinarian decided to try melatonin, and the fur grew back almost immediately.
Infections or parasites
Four out of five cases of hair loss in my dogs were due to an infection. Skin infections in dogs, however, aren’t usually the primary problem. Most of the time, they come secondary to allergies, trauma, immune dysfunction … anything that messes with the skin’s natural defenses. Bacterial skin infections in dogs are primarily bacteria that are normally present on the skin growing out of control–not contagious. Ringworm is a contagious fungal infection.
Allergies can lead to bacterial infections in two ways. Either from self-trauma, such as scratching and biting or the skin’s protective layer disruption due to inflammation. Or both.
Demodectic mange, while a parasitic skin disease, also doesn’t happen in a dog with a healthy immune system. These things live in the hair follicles and cause no harm unless their numbers get out of hand, such as with an immature or compromised immune system. Demodex is not itchy.
Sarcoptic mange (scabies), however, is highly contagious, meaning that most dogs’ immune system has never been equipped to ward these off. Sarcoptes are incredibly itchy and tend to occur on the edges of the ears and lateral elbows.
Hormonal disorders
Poor thyroid function, excessive levels of steroids (Cushing’s disease), high estrogen, and low testosterone can cause symmetrical hair loss.
Too little thyroid hormone and too much cortisol can also be the grounds for secondary infections.
Other causes
Other potential causes include immune disorders, hereditary or congenital issues, nutritional deficiencies, or systemic issues.
Your dog’s skin and coat are a reflection of their health. Any change in coat quality or hair loss is a red flag telling you there is a problem to deal with. When my dog starts losing hair, I not only look at the immediate cause, such as an infection, but I want to see what is going on systematically. Why isn’t the immune system tackling this? Is it too agitated? Is it too weak? Why?
Related articles:
Dandruff/Flaky Skin in Dogs
Further reading:
8 Causes of Hair Loss in Dogs