Hair loss in dogs has dozens of possible causes, but most cases trace back to a handful of common culprits: allergies, parasites, hormonal imbalances, infections, or stress. Some breeds are also genetically prone to specific types of baldness. The pattern of hair loss, where it shows up on your dog’s body, and whether your dog is itching can tell you a lot about what’s behind it.
Allergies and Flea Reactions
Allergies are one of the most frequent reasons dogs lose hair. The hair loss is almost always indirect: your dog itches, scratches or licks obsessively, and the fur comes out from the trauma rather than falling out on its own. Food allergies, environmental allergens like pollen or dust mites, and contact allergies can all trigger this cycle.
Flea allergy dermatitis deserves special attention because it’s extremely common and often misidentified. Dogs with this condition aren’t just bothered by flea bites. They’re allergic to proteins in flea saliva, so even a single bite can set off intense itching that lasts for days. The hair loss concentrates around the base of the tail, lower back, groin, and belly. If your dog is chewing at the area just above the tail and you’re seeing thinning fur there, fleas are a strong suspect even if you haven’t spotted one on your dog.
Mites and Mange
Two types of mange cause hair loss in dogs, and they look and feel very different.
Sarcoptic mange (sometimes called scabies) comes from a burrowing mite that triggers intense, relentless itching. It typically starts on the belly, chest, ears, elbows, and hocks, then spreads across the body if left untreated. The itching is so severe that dogs will scratch themselves raw, and the resulting hair loss is hard to miss.
Demodectic mange is caused by a different mite that lives naturally in small numbers on most dogs. When a dog’s immune system can’t keep the mite population in check, often in puppies or immunocompromised adults, the mites multiply and cause patchy baldness. The localized form produces one to five well-defined bald spots, usually around the lips, eyes, and front legs. The key difference is that demodectic mange causes little to no itching. If your dog has bald patches but isn’t scratching, this is a possibility worth investigating.
Ringworm
Despite the name, ringworm is a fungal infection, not a worm. The fungus attaches to keratin, the protein that makes up hair and nails, and damages the hair shaft until it breaks off. This creates round or irregularly shaped bald patches, often with crusty, scaly skin at the center. Lesions most commonly appear on the face, legs, and tail.
Ringworm patches can be small (just a few millimeters across) or grow larger over time. If the inflammation lasts long enough, the hair loss in that spot can become permanent. Ringworm is also contagious to other pets and to humans, so early identification matters.
Hormonal Imbalances
When hair falls out evenly on both sides of the body without any itching, a hormonal problem is a likely cause. The two most common hormonal conditions behind canine hair loss are hypothyroidism and Cushing’s disease.
Hypothyroidism
The thyroid hormone plays a direct role in keeping hair follicles in their active growth phase. When thyroid levels drop too low, hair follicles prematurely shift into a resting phase. Hair sheds but doesn’t grow back. In mild cases, thinning appears in scattered areas like the thighs and tail. In more advanced cases, hair loss becomes symmetrical on both sides of the trunk. The skin underneath often looks normal, with no redness or sores, which helps distinguish it from allergic or infectious causes. Dogs with hypothyroidism also tend to gain weight, become lethargic, and seek out warm spots.
Cushing’s Disease
Cushing’s disease occurs when the body produces too much cortisol, often because of a small tumor on the pituitary gland or adrenal gland. Like hypothyroidism, it causes symmetrical hair loss on the body. But Cushing’s also thins the skin itself, making it fragile and papery. Dogs with Cushing’s typically drink and urinate far more than usual and develop a pot-bellied appearance. The combination of increased thirst, a distended belly, and bilateral hair loss is a strong signal for this condition.
Stress and Behavioral Causes
Dogs can lick themselves bald. Repetitive licking in one spot creates what’s known as a lick granuloma: a raised, hairless, thickened patch of skin that can become ulcerated over time. These lesions develop most often on the top of the front wrists or ankles, where the dog can easily reach.
The underlying triggers are a mix of psychological and physical factors. An estimated 70% of dogs with lick granulomas have an anxiety-related condition, whether it’s separation anxiety, noise phobia, boredom, or general stress. Dogs that spend long periods alone, live exclusively outdoors, or are confined in crates or on chains are especially prone. That said, the licking sometimes starts because of a minor injury or joint pain in that area, and the behavior continues even after the original irritation heals. This makes it a frustrating condition to untangle, because both the physical wound and the behavioral habit need to be addressed.
Genetic and Breed-Specific Hair Loss
Color Dilution Alopecia
Dogs with “diluted” coat colors, blue (a washed-out version of black) or fawn (a diluted brown or red), are susceptible to a genetic condition called color dilution alopecia. The hair in diluted areas becomes brittle and falls out, typically starting between 4 and 18 months of age, though some dogs don’t show signs until they’re 3 to 6 years old. Blue and fawn Doberman pinschers are the most commonly affected, with incidence rates of about 58% and 90% respectively. The condition has also been reported in Yorkshire terriers, dachshunds, schnauzers, Italian greyhounds, Chihuahuas, whippets, and several other breeds.
Alopecia X
Alopecia X is a mysterious form of hair loss that primarily affects Nordic and plush-coated breeds: Pomeranians, chow chows, keeshonds, Samoyeds, Alaskan malamutes, Siberian huskies, and miniature poodles. Pomeranians are the most commonly diagnosed. The cause remains unknown, which is how the condition got its name. Theories have ranged from growth hormone deficiency to adrenal enzyme problems to overactive estrogen receptors in hair follicles, but none has been confirmed. The hair loss is purely cosmetic, with no itching or discomfort, and typically affects the trunk while sparing the head and legs.
Seasonal Flank Alopecia
Some dogs develop bald patches on their flanks (the sides of the body between the ribs and hips) that come and go with the seasons. This pattern is linked to changes in daylight exposure and the pineal gland’s production of melatonin, the hormone that regulates sleep-wake cycles. Shorter days in fall and winter appear to reduce melatonin output, which disrupts the hair growth cycle in that specific region. The hair often regrows on its own as days lengthen in spring. Melatonin supplements have been used successfully in many affected dogs to prevent or reduce the seasonal episodes. Boxers, bulldogs, and Airedales are among the breeds most commonly affected.
How the Pattern Points to the Cause
Paying attention to where and how your dog is losing hair can help narrow down the cause before you even get to the vet. Symmetrical hair loss on both sides of the body with no itching points toward a hormonal issue. Hair loss concentrated around the tail base and lower back suggests fleas. Circular, crusty patches on the face and legs could be ringworm. A single raw, thickened spot on a front leg is characteristic of a lick granuloma. Patchy bald spots around the eyes and mouth in a young dog raise the possibility of demodectic mange.
Also note whether your dog is itchy. Intense scratching narrows the list to allergies, fleas, or sarcoptic mange. Calm, itch-free hair loss points more toward hormonal disease, genetic conditions, or demodectic mange. Your vet will use this information alongside skin scrapings, blood tests, or fungal cultures to identify the specific cause and recommend the right treatment path.