My Dog Is Losing Hair: Causes of Hair Loss in Dogs

Some shedding is entirely normal for most dog breeds, but hair loss that is patchy, associated with skin changes, or noticeably more than usual is a different matter. Hair loss (alopecia) in dogs has many causes, and the pattern of loss, the condition of the remaining fur, and any accompanying symptoms all point towards different diagnoses.

Is This an Emergency?

Go to a vet the same day if:

• Hair loss is spreading rapidly or is associated with open sores, scabs, or bleeding
• Your dog appears to be in pain at the affected areas
• Hair loss around the eyes or muzzle is accompanied by facial swelling

Book a routine vet appointment if:

• Hair loss is patchy, symmetrical, or involves the trunk
• Thinning is gradual and you cannot identify an obvious cause
• Hair loss is accompanied by skin changes including scaling, redness, or pigmentation changes
• Your dog is also drinking more, has gained weight, or has a pot-bellied appearance alongside hair loss

What Causes Hair Loss in Dogs?

Allergies (atopy and food allergy)

Allergic skin disease causes itching, and the resulting scratching and chewing leads to secondary hair loss. The pattern often reflects where the dog is able to reach, typically the paws, belly, and around the tail base.

Mange (Demodex and Sarcoptes)

Demodectic mange, caused by Demodex mites, is particularly common in young dogs and causes patchy hair loss, often around the face and paws, without severe itching. Sarcoptic mange (scabies) causes intense itching, hair loss, and crusty skin and is contagious to other dogs and humans.

Ringworm (dermatophytosis)

Despite the name, ringworm is a fungal infection, not a worm. It causes circular, scaly, hairless patches and is contagious to humans and other animals. It requires antifungal treatment.

Hypothyroidism

An underactive thyroid causes symmetrical, non-itchy hair loss, often on the trunk and tail, along with weight gain, lethargy, and skin thickening. Diagnosed by blood test and managed with daily medication.

Cushing's disease (hyperadrenocorticism)

Excess cortisol causes bilateral symmetrical hair loss, a pot-bellied appearance, increased thirst and urination, and skin thinning. More common in middle-aged to older dogs.

Seasonal flank alopecia

A benign, cyclical hair loss affecting the flanks, most common in Boxers and Bulldogs, that occurs at the same time each year and regrows spontaneously. Cosmetic rather than medical.

Post-clipping alopecia

Some dogs develop slow or incomplete hair regrowth in an area that has been clipped for surgery or medical procedures. Usually resolves with time.

Which Breeds Are More Prone to Hair Loss?

• Airedale Terrier, Boxer, Bulldog: Seasonal flank alopecia
• Golden Retriever, Dobermann, Irish Setter: Hypothyroidism-related hair loss
• Boxer, Poodle, Dachshund: Cushing's disease
• Staffordshire Bull Terrier, French Bulldog, Shar-Pei: Demodex mange

What Will the Vet Do?

Your vet will examine the pattern of hair loss and the skin condition closely. They may:

• Perform a skin scrape to check for Demodex or Sarcoptes mites
• Take a fungal culture to check for ringworm
• Order blood tests including thyroid levels and a cortisol test
• Refer you to a veterinary dermatologist for complex or unresolved cases

How to Help Your Dog at Home

• Do not shampoo affected skin with harsh or human products, as this can worsen irritation
• If ringworm is suspected, avoid contact between the affected dog, other pets, and vulnerable people (children, elderly, or immunocompromised individuals) until diagnosed and treated
• Keep a record of when hair loss started, whether it is spreading, and any other symptoms you have noticed
• Do not apply any topical treatments without veterinary advice, as the wrong product can worsen mange or hide other diagnoses