Hair Loss (Alopecia) in Dogs

Patchy vs Symmetrical Hair Loss

• Patchy or multifocal: usually inflammation of the hair follicles from bacteria, Demodex mites or ringworm.^3,16
• Symmetrical, both sides: usually hormone disease or non-itchy conditions such as alopecia X, flank alopecia and pattern baldness.^4,5
• Broken hairs: hair chewed or scratched off from itching, which is a sign of allergies or parasites rather than true hair loss.^2,3

Common Causes

• Mites: Demodex (localized patches often clear without treatment, while the generalized form is serious) and Sarcoptes (very itchy and contagious, including to people)^10,11
• Ringworm: patchy hair loss with scale and little itch. It can spread to people.^8,9
• Bacterial infection: "moth-eaten" patches with bumps and rings of peeling skin. See pyoderma.^17,18
• Allergies and fleas: hair loss from scratching and chewing^1,2
• Hypothyroidism: non-itchy loss on the trunk, tail ("rat tail") and bridge of the nose, with a dull coat and slow regrowth after clipping^6,16
• Cushing's disease: symmetrical loss with thin skin on the belly, a pot belly and increased thirst and appetite^5,4
• Sex hormone problems: such as testicle tumors in dogs with retained testicles^2,19
• After pregnancy, nursing, illness or fever: temporary hair loss¹
• Collars, harnesses and friction²

Breed-Related Hair Loss

• Alopecia X ("black skin disease"): non-itchy, symmetrical loss with darkened skin, usually starting in young adults. It affects Pomeranians, Poodles and Nordic or plush-coated breeds such as Chow Chows, Keeshonds, Samoyeds and Siberian Huskies. The head and lower legs are spared. It's mainly cosmetic.^20,5
• Seasonal flank alopecia: hair loss on the flanks in fall or winter, often with dark skin, regrowing in spring or summer. It's most common in Boxers, Bulldogs and Airedales.^21,5
• Pattern baldness: thinning on the ears, neck, chest and belly in young Dachshunds, Boston Terriers and Chihuahuas⁵
• Color dilution alopecia: thinning and scaling in blue or fawn dogs, especially blue Dobermans, starting at 6 months or older. Hair loss is permanent.^7,5
• Post-clipping alopecia: hair that doesn't grow back after shaving, mainly in plush-coated breeds. Most regrow within a year.¹⁵

Diagnosis

Your vet will ask when the hair loss started and whether your dog is itchy, then examine the hairs to see whether they're shed or broken.^1,2 Common tests include skin scrapings and combing for parasites, cytology for infection, ringworm tests, and blood and urine tests if hormone disease is suspected.^2,8 A normal thyroid blood test (total T4) alone can't rule out hypothyroidism, and a skin biopsy may be needed for unusual cases.^5,2

Treatment

Treatment depends on the cause:^2,5

• Parasites: parasite medicines from your vet^11,10
• Ringworm: antifungal pills plus medicated baths or dips, and cleaning the home⁸
• Bacterial infection: antiseptic shampoos, and antibiotics if needed²²
• Allergies: itch control and allergy management²³
• Hormone disease: treatment after a confirmed diagnosis. Coat improvement with thyroid treatment can take several months.^5,6
• Alopecia X: since it's cosmetic, it may be left untreated. Options include spaying or neutering, melatonin and other treatments, but none works for every dog.^20,24

Some forms, such as flank alopecia and post-clipping alopecia, usually regrow on their own.^21,15

Frequently Asked Questions

Why is my dog losing hair in patches?

Patchy hair loss is most often caused by mites, ringworm or bacterial infection.

Will my dog's hair grow back?

Usually, once the cause is treated, though it may take months. Color dilution alopecia and scarring are permanent.

Can stress cause hair loss in dogs?

Severe illness, fever, pregnancy and nursing can cause temporary hair loss.

Can I catch my dog's hair loss?

Ringworm and sarcoptic mange can spread to people. Most other causes can't.

What is black skin disease in dogs?

Another name for alopecia X, a non-itchy hair loss in Pomeranians and other plush-coated breeds.