There are many diseases and conditions which can cause a dog to lose hair. Some of these may be considered normal, others can indicate a serious disease is present. Most of the conditions which result in hair loss are included in the table below, though some of them may be rare. This extensive list helps you understand why a quick diagnosis may be difficult to make, and various diagnostic tests may need to be performed. The most common conditions causing hair loss are color-coded gray in the table (some may be more common in certain geographical areas).

Condition Description Symptoms Diagnosis Treatment
Acanthosis nigricans Inherited form seen in Dachshunds; secondary form caused by friction, hormonal abnormalities, or hypersensitivities Darkening of the skin; in secondary form see scratching and hair loss History, physical exam; in secondary form, testing to determine underlying cause Primary: no treatment; secondary: treat underlying disease; in some cases, steroids and Vitamin E supplementation

Acral lick dermatitis (neurodermatitis)

Self-licking in dogs results in self-trauma; possible causes include anxiety, boredom, stress (e.g., new member in household); licking can develop into an obsessive behavior

Red, hairless, well-circumscribed, sometimes raised lesion usually on the leg; if chronic, will drain

Exclude other causes; history important

Relieve underlying cause e.g., anxiety; restrict licking, e.g., elizabethan collar; behavior modifying medication may be necessary

Adrenal sex hormone responsive dermatosis More common in Pomeranians, Chows, Keeshonden, and Samoyeds Hair loss starts on neck, tail, back of thighs, and progresses to trunk; dog appears to have a 'puppy coat'; skin darkens Biopsy; eliminate other causes Mitotane is optional

Allergic and irritant contact dermatitis

An allergic reaction following exposure to antibiotics applied to the skin; metals such as nickel; materials such as rubber, wool, and plastic; and chemicals such as dyes and carpet deodorizers; or inflammation caused by irritating substances such as poison ivy. Generally requires multiple exposures.

Red skin and small bumps or blisters on the areas of skin that are sparsely haired and directly exposed to the offending substance, itching; hair loss in chronic conditions

Patch test, exclusion trials

Restrict exposure to the allergen or contact irritant in the dog's environment; steroids, antihistamines

Alopecia areata

(also Flank Alopecia)
Thought to be an autoimmune disorder Patches of hair loss especially on head, neck, and body; no itching Microscopic examination of hairs; biopsy Usually recover spontaneously

Atopy (allergic inhalant dermatitis)

Allergic reaction to something the dog inhales such as pollen, house dust mites, and mold

Licking of feet, inflamed ears, itching, redness, and hair loss; sometimes development of infection or hot spots

Intradermal or serologic (blood) testing for allergies

Reduce exposure to allergen (what the dog is allergic to); steroids, fatty acid supplements, biotin, antihistamines, shampoos, immunotherapy

Bacterial infection (pyoderma)

See Folliculitis

Often occurs as a result of another condition such as a parasitic, allergic, or hormonal condition

Black hair follicular dysplasia/alopecia/dystrophy Rare hereditary disease in dogs with hair of multiple colors; more common in Bearded Collies, Basset Hounds, Salukis, Beagles, Dachshunds, and Pointers Loss of dark or black hair only; symptoms appear between 3 and 6 weeks of age; sometimes scaling Clinical signs, biopsy Shampoos for scaling if necessary
Callus Results from chronic pressure, especially in large breed dogs Thickened, hairless raised areas over bony pressure points such as elbows; may become secondarily infected History, clinical signs Provide softer bedding and padding around affected area
Castration responsive dermatosis More common in young unneutered dogs, and in Chows, Samoyeds, Keeshonden, Alaskan Malamutes, Miniature Poodles, and Pomeranians Symmetrical hair loss in genital area and neck; hair loss may progress onto trunk; skin may appear darker; severe scaling; hair color may fade; coat is similar to a 'puppy coat' Physical exam and history; eliminate other causes; blood tests for hormone levels Castration
Chemotherapy Loss of hair due to chemotherapy is a concern for dog owners Dogs with continuously growing hair, e.g., Poodles and Maltese, often lose some hair; dogs may lose whiskers History None, hair will regrow after chemotherapy discontinued; may regrow in a different color or texture

Cheyletiella (rabbit fur mite) mange

Infection with the Cheyletiella mite

Itching, scaliness; some hair loss, if severe

Skin scraping and microscopic examination - the mite is often very difficult to find

Pyrethrin, Permethrin (Do NOT use permethrin on cats.)

Color dilution/mutant alopecia Hereditary condition affecting dogs with blue (diluted black) or fawn coat colors; more common in Dobermans, Dachshunds, Great Danes, Yorkshire Terriers, Whippets, and Greyhounds Hair in the blue- and fawn-colored areas starts to thin at around 6 months of age; secondary folliculitis often develops Breed; history; and coat color None; avoid excessive grooming or harsh shampoos; protect skin to prevent secondary bacterial infections
Congenital hypotrichosis Congenital lack of hair Puppies born with little or no hair; any hair they are born with is lost by 4 months of age Physical exam; biopsy None
Cushing's disease (hyperadrenocorticism) Caused by an increase in corticosteroids in the body - either due to increased production by the body or as a side effect of high doses or prolonged therapy with corticosteroids Hair loss, thinning of skin, hyperpigmentation, easy bruising, seborrhea, comedones (black heads), may see calcinosis cutis; lethargy, increased thirst and urination, potbellied appearance Adrenal gland function tests, urinalysis, chemistry panel, CBC If due to glandular tumors, selegiline, o,p-DDD (Mitotane), or surgical removal of tumor; if due to high steroid doses, withdraw use of steroids slowly
Cyclic (cicatrical) alopecia; seasonal flank alopecia Growth cycle of hair stops at certain times of the year Symmetrical hair loss with definite borders; usually on back and flanks; skin may become darker History, clinical signs, biopsy None

Demodectic mange
(red mange, puppy mange)

Infection with the Demodex mite - occurs when the immune system is deficient

Hair loss, scaliness, redness, pustules, ulcers, sometimes itching, darkening of the skin

Skin scraping and microscopic examination

NO Steroids!

Amitraz (Mitaban) dips

Dermatomyositis Some breeds predisposed; cause unknown; aggravated by trauma and UV light Redness, scaling, crusting, hair loss, and scarring on face, ears, and tail; atrophy of muscles involved in chewing Skin biopsy Minimize trauma and exposure to UV light; Vitamin E, fatty acids, short term use of prednisone, oxpentoxifylline; some severe cases do not respond to treatment, and euthanasia may be considered
Diabetes mellitus Abnormal immunity makes diabetic dogs susceptible to infection and other skin conditions Thin skin; some hair loss; seborrhea; recurrent bacterial infections; unregulated dogs also have many other signs of disease; may develop epidermal metabolic necrosis or xanthoma Blood testing Dietary changes; insulin
Drug or injection reaction Rare skin reaction to a drug which is inhaled, given orally, or applied topically; more common with penicillins, sulfonamides, and cephalosporins; usually occurs within 2 weeks of giving the drug Can vary widely and may include itching, hair loss, redness, swelling, papules, crusts, ulcers, and draining wounds History of being treated with a drug, symptoms, biopsy Discontinue offending drug; treat symptomatically
Epidermal metabolic necrosis (necrolytic migratory erythema, hepatocutaneous disease) Uncommon skin disease in older dogs; skin lesions develop in dogs with certain diseases including liver disease, diabetes mellitus, and some pancreatic tumors Reddened, often ulcerated areas with hair loss and crusts; foot pads may be thickened Biopsy; look for underlying disease Treat underlying disease; supportive therapy; poor prognosis
Erythema multiforme Hypersensitivity reaction to infections or drugs; may also be caused by cancer or other diseases Hair loss, 'bull's-eye' lesions, and vesicles often around mouth, ears, groin, and axilla; in some instances, ulcers develop; depression, fever History, clinical signs, rule out other diseases causing similar signs; skin biopsy Treat or remove underlying cause
Estrogen responsive dermatosis (ovarian imbalance type II) More common in young spayed dogs, and in Dachshunds and Boxers Hair loss starting at the genital area and flanks and moving forward; hair color may fade; coat is similar to a 'puppy coat' Physical exam and history; eliminate other causes; response to therapy Estrogen replacement therapy; caution - can have severe side effects

Flea allergy dermatitis (flea bite hypersensitivity)

Severe reaction by the animal to the saliva of the flea

Intense itching, redness, hair loss papules, crusts, and scales; sometimes development of infection or hot spots

Presence of fleas; reaction to intradermal testing

Flea control in the environment and on the dog; steroids and antihistamines for the itching

Follicular dystrophy/alopecia/dysplasia (abnormal development or growth of hair)

See Congenital hypotrichosis, Color dilution/mutant alopecia, Black hair folliclular dystrophy/alopecia, Follicular dysplasia (non-color linked)

May be congenital (certain breeds are at increased risk) or acquired later in life from infections, hormonal abnormalities, cancer drugs, and some other diseases Hair loss, sometimes only hair of a certain color; sometimes scaling Clinical signs, breed, skin biopsy In congenital disease, treatment of secondary problems such as infections or scaling; in acquired disease treat underlying cause
Follicular dystrophy/dysplasia (non-color linked) Patchy hair loss of unknown cause seen in the Siberian Husky, Doberman Pinscher, Airedale, Boxer, Staffordshire Bull Terrier, Curly Coated Retriever, Irish Water Spaniel, and Portuguese Water Dog In Huskies, hair loss on the body, reddish tinge to hair; in Dobermans, hair loss over lumbar area; in Boxers and Terriers, hair loss over lumbar area, skin may be hyperpigmented; in the Retrievers and Spaniels, loss of guard hairs on back and trunk and secondary hairs are dull and lighter in color Breed, biopsy None
Folliculitis Infection of the hair follicles, often with staph bacteria; symptoms usually appear on skin with less hair, such as the abdomen Pustules form in follicles and break open to form 'bull's-eye,' 'annular,' and 'target lesions,' which have crusty centers and red or darkening on the periphery, and 'epidermal collarettes,' which appear as rings of scaly skin; may itch; short-coated breeds may develop small tufts of hair, which are lost; breeds with long coats may have seborrhea Skin scraping; culture; biopsy Antibiotics for at least 4 weeks - continue antibiotics 10 days beyond the apparent cure; if recurs, look for underlying problem such as allergy or hormonal imbalance

Food allergies

Allergic reaction to something in the diet

Licking of feet, inflamed ears, itching, redness, and hair loss; sometimes development of infection or hot spots

Food elimination trials

Change in diet

Granulomas May be due to infections; the body's reaction to foreign material such as plant material (e.g., foxtail) and suture material; other constant irritation; or unknown causes Solid firm nodules of varying sizes; those due to foreign bodies often have draining tracts; may develop hair loss, ulcers, and secondary infections History, clinical signs, biopsy, surgical exploratory Surgical removal of the foreign body (in the case of plant material, tracts may be extensive and require major surgery); antibiotics if infected; treat any other underlying cause
Growth hormone responsive alopecia Not well understood; thought to be caused by an enzyme deficiency or decrease of adrenal hormones, which allows certain other hormones to accumulate in the body: more common in Pomeranians, Chow Chows, Keeshonden, Samoyeds, and Poodles Hair loss on neck, tail, and the back of the thighs; skin darkens; usually starts when dog is less than two years old Hormonal blood testing Neuter animal; growth hormone; hormonal supplementation

Growth Hormone Treatment: 
Growth hormone (somatotropin) is a polypeptide produced by the anterior pituitary that acts either directly on target tissues or indirectly through insulin-like growth factors (somatomedins) produced by the liver. It is necessary for hair growth and for development of elastin fibers in the skin. It is used to treat growth hormone-responsive alopecia in dogs. Either bovine, porcine, or human growth hormone (0.1 IU/kg, 3 times/wk for 4-6 wk) is effective. Hair usually regrows in 2-3 mo, and remission may last from 6 mo to 3 yr. Growth hormone is diabetogenic, and dogs can develop transient or permanent diabetes mellitus during therapy. Weekly monitoring of blood glucose before and during therapy is recommended. 

Hair loss during pregnancy and nursing ('blowing her coat,' telogen effluvium) Excess shedding that can also occur in other stressful circumstances such as illness or surgery Sudden and widespread hair loss History, clinical signs Treat any underlying condition; hair will grow back
Histiocytosis There are several kinds of histiocytosis: malignant, which is a cancer that affects the skin and internal organs; systemic, which is a rare disease which affects skin and internal organs; and cutaneous, which is a benign disease affecting the skin All cause nodules with hair loss; malignant and systemic also have ulcers Biopsy, fine needle aspirate; Malignant: none effective, may need to consider euthanasia; systemic: poor response to chemotherapy; cutaneous: corticosteroids, relapse is common, especially in Shar-Peis
Hyperestrogenism (ovarian imbalance type I) Rare disease in which female animals have excess levels of estrogen; can be caused by cancer of the ovaries Symmetrical loss of hair; hair pulls out easily; darkening of the skin; enlarged nipples and vulva; may rarely see seborrhea and itching History, physical exam, rule out other causes of hair loss, measure blood estrogen levels Spay; look for metastasis to the lungs
Hypothyroidism Decreased production of thyroid hormone; most common hormonal disease affecting the skin in dogs Hair loss, dry and brittle hair, seborrhea; secondary bacterial and yeast infections; lethargy, obesity, slow heart rate; changes in skin pigmentation may occur Thyroid gland function tests, chemistry panel, CBC Lifetime thyroid supplementation
Injection site alopecia Hair loss at the site of an injection of a medication or vaccine; skin may become thickened; in cats, ulcers may develop Hair loss occurs several months after injection; area may become hyperpigmented History and physical examination None; the condition is permanent
Interstitial cell tumor Tumor of the testicle; may not cause any skin changes If skin changes occur, see seborrhea, loss of hair on the trunk, enlargement of the tail gland and perianal glands; may see increased pigment in the skin Biopsy Castration; anti-seborrheic shampoos
Kerion Complication of ringworm infection Nodule with hair loss and multiple draining tracts; may not see other signs of ringworm Culture, biopsy Clip area and apply topical treatment and shampoos; may require systemic treatment with ketoconazole or itraconazole
Leishmaniasis Caused by a parasite of blood cells; can be transmitted to people who develop a very severe disease Hair loss, scaling, ulcers on nose and ears, sometimes nodules; many other nonskin-related signs Identify the organism in blood or biopsy; blood tests Because it causes severe disease in people, and treatment of dogs is not curative, euthanasia may be performed


Infection with several species of lice

Variable; itching, hair loss, crusts, rough hair coat

Finding lice or nits on skin or hair

Pyrethrin, ivermectin (off-label use*), Permethrin (Do NOT use permethrin on cats.)


Usually follows some other underlying disease

Itching, redness, hair loss, greasy scales; if chronic, develop hyperpigmentation

Skin scraping/smear and microscopic examination, culture

Treat underlying disease; oral ketoconazole; miconazole shampoos

Nasal solar dermatitis

See solar dermatitis

See solar dermatitis      
Pattern alopecia (pattern baldness) Three types; hair loss may occur on the ears of Dachshunds (pinnal alopecia); neck, thighs, and tail of American Water Spaniels and Portuguese Water Dogs; abdomen and the back of the thighs of Dachshunds, Chihuahuas, Whippets, and Greyhounds Hair loss in described areas Breed, history, biopsy None

Pelodera dermatitis

Accidental infection with larvae from a non-parasitic worm that lives in straw and other organic material

Affects areas of skin touching ground; intense itching, redness, hair loss, papules, crusts, and scales

Skin scraping and microscopic examination

Remove bedding; mild antibacterial shampoo; steroids if necessary to control itching

Pituitary dwarfism Hereditary condition in which the pituitary gland does not produce the necessary hormones Young puppies fail to grow; dogs retain puppy coat and condition progresses to hair loss over much of the body; thin skin, scales, and secondary infections Special blood testing for the presence of certain hormones Hormone replacement therapy
Post-clipping alopecia Hair may not grow back immediately after it has been clipped; which animals may be affected can not be predicted; more common in dogs with thick undercoats e.g., Huskies and Chows Continued lack of growth in hair that was clipped, e.g., for surgery History None; hair will eventually regrow, but may take up to 24 months
Pressure sores (decubital ulcers) Lesions occur over bony prominences like elbows; common in larger recumbent dogs Start as red, hairless areas and progress to draining ulcers; may become infected Clinical signs, biopsy Keep area clean and prevent contact with urine; antibiotics; apply donut bandages, which provide padding around but not over the ulcer; surgical treatment is sometimes necessary; prevent ulcers by turning the dog every 2 hours

(See Folliculitis)



Infection with several types of fungus

Hair loss, scaliness, crusty areas, pustules, vesicles, some itching; can develop a draining nodule called a 'kerion'


Miconazole, lime sulfur dips; oral griseofulvin or itraconazole

Sarcoptic mange

Infection with the Sarcoptes mite

Intense itching and self-trauma, hair loss, papules, crusts, and scales

Skin scraping and microscopic examination - the mite is often very difficult to find

Amitraz (Mitaban) dips (off-label use*); ivermectin (off-label use*)

Schnauzer comedo syndrome Uncommon; only seen in Miniature Schnauzers Comedones (black heads) on back, mild itching; may see secondary infection, thinning of hair; small crusts may develop Clinical signs, breed, skin biopsy Long-term antiseborrheic shampoos; sometimes antibiotics and retinoids
Sebaceous adenitis Sebaceous glands are destroyed, cause unknown; certain breeds more susceptible Short-haired breeds: circular areas of hair loss with fine scale; long-haired breeds: more widespread hair loss and scale, hair mats easily; may see itching in all breeds Clinical signs, breed, skin biopsy Antiseborrheic shampoos, fatty acid supplements; in more severe cases, steroids, retinoids
Seborrhea Can be primary (inherited) or secondary (resulting from other disease processes such as allergies, hypothyroidism) Scales; depending upon the type, may have a dry or oily coat; odor; some scratching; may see hair loss Blood tests, skin scrapings, etc., to find underlying cause Treat underlying cause if present; antiseborrheic shampoos; fatty acid supplements
Sertoli cell tumor Tumor of the testicles in middle-aged dogs Male dogs take on female sexual characteristics; hair loss, increased skin pigment, reddened area on prepuce Physical exam Castration
Solar dermatosis Skin reaction to sunlight, especially unpigmented skin; most common on the noses of Collies, Shelties, and similar breeds Redness, hair loss, and scaling on nose and ears, later crusts and ulcers History, breed, physical exam, skin biopsy Must avoid further sun exposure, especially 9 am - 3 pm; sunblock; steroids; tattoo nose or apply black ink
Tail dock neuroma Nerve regrowth after tail docking causes symptoms Nodule at site of docking, itching with self-mutilation, hair loss, and hyperpigmentation History and symptoms Surgical removal
Tail gland hyperplasia Dogs have a sebaceous gland on the top of the tail near its base; in this disorder, the gland enlarges; seen in unneutered dogs and secondary to other diseases such as hypothyroidism Oily area, hair loss, crusts, and hyperpigmentation on area over gland Clinical signs; look for underlying cause Castration may help; treat underlying cause; surgical removal
Testosterone responsive dermatosis (hypoandrogenism) More common in old neutered dogs, and in Afghans Dull, scaly, dry coat; seborrhea; hair loss in genital and anal areas progressing onto trunk Physical exam and history; eliminate other causes; response to therapy Testosterone replacement therapy
Vitamin A responsive dermatosis May not be due to an actual deficiency of Vitamin A, but does respond to increased levels of Vitamin A in the diet; more common in Cocker Spaniels Seborrhea; odor; hair pulls out easily; pads of feet thickened; thick scales on chest and abdomen, especially around nipples Clinical signs, breed, skin biopsy Lifetime treatment with Vitamin A
Zinc responsive dermatosis Three types: I in Huskies and Malamutes; II in rapidly growing puppies of large breeds; III in English Bull Terriers Crusting and scaling, redness, hair loss, sometimes oily skin, secondary bacterial infections common History, breed, physical exam, skin biopsy Correct any dietary deficiency, medicated shampoos, treat secondary infections

* off-label use: medication used to treat a condition for which it was not developed (or licensed). A large number of medications fall under this category. Research has almost always been performed to determine the effectiveness and safety of the product, but the manufacturer has not undertaken the lengthy process required for licensure.

Holly Nash, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.


What Is The Most Common Cause Of Hair Loss?

Fleas are the number one cause of scratching and hair loss. Flea bites cause intense itching so pets literally scratch their hair out. Dogs create areas of patchy baldness at the base of the tail, abdomen, and back of the legs. Cats tear out, or barber hair to rid themselves of fleas, creating bald patches on bellies and flanks. The scratching breaks the skin allowing secondary bacterial and yeast infections. 

What else causes hair loss? 

Here are 14 additional causes of hair loss

  1. Flea Allergy Dermatitis is confirmed by finding flea dirt.

  2. Ringworm causes patchy baldness, sometimes with scaling. Cats can have ringworm and transmit it to other pets without any visible sign of having ringworm.

  3. Behavioural problems, like anxiety and boredom, stimulate scratching and chewing. Keep the pet busy and well exercised. Treat obsessive disorders. Treat anxiety with calming pheromones and herbs. Provide toys.

  4. Food allergies cause itching year round, regardless of fleas or pollens. Dogs scratch their feet, front legs, and ears. Cats scratch their head and neck.

  5. Mites and Lice affect the back, the base of the tail, and back of legs. Mites and lice are spread by pets, wild animals, bedding. Identify the parasite with skin scrapings and microscopic exams. Work with your veterinarian to identify the parasite with skin scrapings and microscopic exams.

  6. Red Mange is caused by the Demodex mite. It affects ears, elbows, head; is intensely itchy; and may indicate immune system weakness. Red mange is rare in cats unless they have FIV, FIP, or FeLV.

  7. Thyroid disease in cats is usually due to an over-active or “hyper” thyroid that stimulates “barbering” where the cat tears out its hair. Hyperactive cats have bald patches on belly and flanks. In dogs, thyroid disease is usually due to under active or “hypo” thyroid gland. Hypothyroid dogs often have thin coats.

  8. Adrenal disease (Cushing’s disease or hyperadrenocorticism) causes hair loss on the trunk and most of tail, but the tip is spared—“rat tail.”

  9. Diabetes causes poor skin healing, unkempt hair coat. Pets lose weight, have sugar in their urine.

  10. Cancer occurs in the skin (squamous cell) or in other organs that affect the skin (paraneoplastic disease). Skin cancer is most common in white or nonpigmented areas. Paraneoplastic disease occurs in geriatric pets, often because of pancreatic cancer, and causes hair loss around eyes, bridge of nose, and belly.

  11. Sebaceous gland inflammation (sebaceous adenitis) can be caused by toxins or immune dysfunction that destroys the skin’s sebaceous glands. Skin along the back and down the legs is scaly and hairless.

  12. Sex Hormone Responsive Dermatosis is usually symmetrical, and occurs under the tail, along flanks, the belly, the rump, and collar.

  13. Growth Hormone Responsive Dermatosis causes symmetrical baldness along trunk with increased pigmentation.

  14. Autoimmune Diseases like Pemphigus cause patchy hair loss and scaling as the immune system attacks the body’s own cells.


Seasonal Affective Disorder Can be Culprit for Canine Hair Loss - read article



Main Categories