A bald patch on your dog’s leg, a coat that slowly thins over the back, or fur that just does not grow back after a clip: hair loss can be dramatic or easy to miss. Vets call it alopecia. It is a sign of something else going on, so the useful question is always what is causing it. [1]
This guide walks through the main causes, how to tell normal shedding from a problem, and what to expect at the vet.
Have a cat? See our guide to hair loss in cats.
Normal shedding or hair loss?
All dogs shed as old hairs make way for new ones. Shedding on its own leaves the coat looking full. What deserves a closer look is hair loss you can see: bare spots, thin patches, or a coat that is getting sparser in the same places on both sides of the body.
So the questions to ask are: Are there actual bare spots? Is the thinning the same on both sides of the body? Is the skin red, scaly, darker or itchy?
Itchy or not itchy: the first big clue
Whether your dog is itchy splits the likely causes into two broad groups. When a dog scratches, licks and chews, the hair breaks and falls out, so itchy skin diseases such as allergies and flea bite allergy often end up with bald, darkened, thickened patches over time. [2] Hormonal diseases and many inherited coat problems, on the other hand, usually cause hair loss without much itch or inflammation. [1][4][5]
Hair loss with itching
- Allergies and fleas. In allergic dogs, hair loss tends to show up later, as a result of constant scratching and licking and of the skin infections that follow. [2] See why is my dog so itchy? and seasonal allergies in dogs.
- Bacterial skin infection. Superficial skin infection is one of the usual suspects when a dog has round, clearly edged bald spots. [3] See pyoderma in dogs.
- Hot spots. A sudden, moist, painful bald patch is often a hot spot. See hot spots on dogs.
Hair loss that may not itch
- Ringworm. This fungal skin infection is another common cause of patchy hair loss, and it can pass from pets to people. [3][8] See ringworm in dogs and cats.
- Hormonal disease. An underactive thyroid, an overactive adrenal gland (Cushing disease) and sex hormone problems all slow or stop hair growth. The loss is typically even on both sides, spares the head and lower legs, and is not itchy unless a skin infection sets in. [4][5][6]
- Inherited coat conditions. These usually cause hair loss without inflamed skin and often follow a pattern tied to the breed or coat color. [1]
Demodex mange, especially in young dogs
Most dogs carry a few Demodex mites deep in their hair follicles. Puppies pick them up from their mother in the first days of nursing, and in small numbers the mites do no harm. This kind of mange is not considered contagious. [3] Trouble starts when the dog’s immune response lets the mites multiply, which inflames the follicles and makes the hair fall out. [3]
There are two main patterns: [3]
- Localized. Typically seen in dogs younger than a year: a few small bald patches, often with some redness, scale or darker skin. Most of these clear up on their own, though a small share go on to the generalized form. Itch is usually mild unless a skin infection joins in.
- Generalized. Many patches across the body, a whole region such as the face, or two or more paws involved. The skin can become red, scaly, greasy, darker and dotted with blackheads and pimple-like bumps, and deep infection can develop. In young dogs there seems to be an inherited tendency. When it first appears in a dog aged 4 or older, it is often tied to another illness that weakens the immune system, such as Cushing disease, an underactive thyroid or cancer, or to long-term medicine that suppresses the immune system.
Vets confirm demodex mange by finding the mites, usually on deep skin scrapings or by looking at plucked hairs under the microscope. [3] Treatment is guided by repeat scrapings, so expect several rechecks before your vet calls it cleared. Because the generalized form in young dogs runs in families, dogs that have had it should not be bred. [3]
Hormonal causes in adult dogs
Hormonal hair loss is usually even on both sides of the body and not itchy or inflamed unless a skin infection develops. [4][5][6]
- Hypothyroidism (underactive thyroid). Typical skin signs are even, non-itchy hair loss over the trunk, often with darkened skin and sometimes a bald “rat tail.” Many dogs also gain weight without eating more, seem tired and dislike the cold. [4] See also dog dandruff and dry, flaky skin.
- Cushing disease (hyperadrenocorticism). Owners often notice more drinking, urinating, eating and panting along with the hair loss. The skin can become thin, darker and show blackheads on the belly. [5] For hard, chalky deposits in the skin, see calcinosis cutis in dogs.
- Sex hormone problems. In dogs that are not spayed or neutered, hormone-producing tumors or cysts of the testicles or ovaries can cause symmetric hair loss that often starts around the rear end, groin and flanks. Vets consider this once thyroid and adrenal disease have been ruled out. [6]
Other causes
- Hair that does not grow back after clipping. After a clip for surgery or grooming, the coat usually grows back within a few months. In some otherwise healthy dogs, especially those with thick, plush coats, it takes much longer. A clipped patch that stays bare is still worth showing your vet, since hormonal disease can look the same. [7]
- Pattern baldness. Some short-coated breeds, including Dachshunds, Greyhounds and Chihuahuas, gradually lose hair in typical places such as the ear flaps, neck, belly or back of the thighs, usually starting before a year of age. [1]
- Less common causes. Your vet may also think about diet, rubbing from a collar or harness, and skin tumors. See lumps and bumps on dogs.
Inherited and breed-related hair loss
Some hair loss is built into a dog’s genes. Examples: [1]
- Color dilution alopecia affects some dogs with blue or fawn coats, the diluted versions of black and brown. It is especially common in blue and fawn Doberman Pinschers. Hair in the diluted areas is gradually lost, usually starting between a few months and 3 years of age.
- Black hair follicular dysplasia affects only the black areas of two- or three-colored dogs and shows up very early, at around a month old.
- Seasonal flank alopecia causes bald, often darkened patches on both sides of the trunk. Boxers, Airedale Terriers and English Bulldogs are at higher risk. In the northern hemisphere the hair tends to fall out in late fall and regrow in spring or summer.
- Alopecia X is seen mostly in plush-coated breeds such as Pomeranians, Chow Chows, Keeshonds and Samoyeds. The coat first turns dull and dry, then loses its outer guard hairs and looks like puppy fur, and later bald, dark patches appear on the neck, lower back, rear and thighs.
Because skin with abnormal follicles is more prone to infection and sunburn, care for these dogs focuses on preventing skin infections and protecting bald areas from the sun. [1]
If the bare skin is also turning dark and thick, see dark skin patches on dogs.
What your vet will check
Finding the cause starts with your dog’s story and a full exam. Your vet will want to know your dog’s breed and age, when the hair loss started and how it has changed, whether there is itching, and how your dog is doing in general, including drinking, eating and energy.
The exam and tests may include: [1][3][4][5][8]
- The pattern and distribution of hair loss
- Looking at plucked hairs under the microscope to see if they are breaking or falling out
- Skin scrapings and flea combing for mites and fleas
- Cytology and cultures for bacteria, yeast or ringworm fungus
- A skin biopsy when earlier tests do not give an answer
- Blood and urine tests if a hormonal problem is suspected
Treatment depends on the cause, which is why finding it comes first.
When to see your vet
Book a visit if:
- You see bald patches, or the coat is thinning on both sides of the body
- The skin is red, scaly, crusty, darker, or has bumps or a smell
- Your dog is scratching, licking or chewing at the area
- A puppy has small bald, red or scaly spots, so your vet can check for mites
- Your dog seems unwell, or drinks, eats or urinates more than usual
- Anyone in the home develops an itchy or ring-shaped rash
FAQ
Is my dog’s shedding normal?
If the coat still looks full and there are no bald patches or matching thin areas on both sides, it is most likely ordinary shedding. Bald spots or an obviously thinner coat are worth a vet visit.
Why is my dog losing hair but not itching?
Hormonal conditions such as hypothyroidism or Cushing disease, demodex mange in its early stages, and inherited coat conditions can all cause hair loss with little or no itch. [1][3][4][5] Your vet can tell them apart with an exam and tests.
Will my puppy’s bald spots go away?
Localized demodex mange is common in dogs under a year old, and most cases clear up on their own. A few spread, and ringworm and skin infection can look similar, so have your vet confirm the cause. [3]
Why hasn’t my dog’s hair grown back after clipping?
The coat usually regrows within a few months, but in some healthy dogs, particularly thick-coated ones, it can take much longer. If a clipped area stays bare, ask your vet to rule out a hormonal problem. [7]
Will my dog’s hair grow back?
It depends on the cause. When hair loss comes from a treatable problem such as infection, parasites or a hormonal disease, treating that cause is the first step. Some inherited conditions are lifelong. [1][4]
The bottom line
Hair loss in dogs is a sign, not a diagnosis. Start by noticing whether your dog is itchy, whether the loss is patchy or symmetric, and whether your dog is otherwise well. Your vet can then work through infections, parasites, allergies, hormones and inherited causes to find the reason and the right treatment.
This article is for general information and is not a substitute for veterinary advice. If your dog is losing hair or has skin changes, please see your veterinarian.
Sources
- Torres SMF. 1.8 Non-Endocrine Alopecias: Learning Objectives and General Considerations. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/non-endocrine-alopecias-general-consideration/
- Hensel P, Santoro D, Favrot C, Hill P, Griffin C. Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification. BMC Vet Res. 2015;11:196. https://pmc.ncbi.nlm.nih.gov/articles/PMC4531508/
- Torres SMF. 3.1 Canine Demodicosis. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/canine-demodicosis-new/
- Torres SMF. 1.5 Hypothyroidism: Canine. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/hypothyroidism-canine/
- Torres SMF. 1.2 Hyperadrenocorticism: Canine. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/hyperadrenocorticism-canine/
- Torres SMF. 1.7 Sex Hormone Dermatoses: Canine. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/sex-hormone-dermatoses-canine/
- Torres SMF. 1.13 Canine Post-clipping Alopecia. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/canine-post-clipping-alopecia/
- Torres SMF. 4.1 Dermatophytosis: Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/dermatophytosis-dogs-and-cats/