Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Hair loss (alopecia) in dogs has many causes. The most common are parasites (fleas and mites), allergies, and skin infections. Hormone problems like hypothyroidism and Cushing’s disease cause symmetrical, non-itchy hair loss. Some breeds have specific conditions, like Alopecia X in Pomeranians or seasonal flank alopecia. Whether the dog is itchy is one of the biggest clues.
Itchy hair loss
- Fleas and flea allergy
- Environmental or food allergies
- Sarcoptic mange
- Bacterial or yeast skin infections
Non-itchy hair loss
- Hypothyroidism: thinning coat, “rat tail”
- Cushing’s disease: thin skin, pot belly, increased thirst
- Demodex mites, often in young dogs
- Ringworm (can be itchy or not)
- Alopecia X in Pomeranians, Chow Chows, and other plush breeds
- Seasonal flank alopecia
- Hair not regrowing after clipping
Other causes
- Pressure points like elbows
- Stress-related licking
- Normal seasonal shedding
What your vet may do
- Skin scrapings and cytology
- Fungal culture
- Bloodwork including thyroid and adrenal tests
- Skin biopsy
When to see a vet
- Patches of hair loss, redness, or scabs
- Itching that disrupts sleep
- Symmetrical thinning with other signs
Sources
- Merck Veterinary Manual: Alopecia in dogs
- Merck Veterinary Manual: Hypothyroidism in dogs
- Merck Veterinary Manual: Mange in dogs
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.