Dog Hair Loss: Causes, Patterns & What to Do

Normal Shedding vs. Abnormal Hair Loss

Every dog sheds. It is a natural part of the hair growth cycle, and the amount of shedding varies enormously by breed, coat type, and season. Double-coated breeds like Huskies, German Shepherds, Golden Retrievers, and Samoyeds are notorious for heavy shedding, especially during their biannual "coat blow" in spring and fall when they shed their undercoat. Single-coated breeds like Poodles, Maltese, and Yorkshire Terriers shed very little but still lose some hair over time.

Normal shedding produces loose fur that comes out during brushing, petting, or just living life. The key characteristic of normal shedding is that it does not leave bald patches. Your dog's coat remains full and even, even if there are tumbleweeds of fur under the couch. The skin underneath looks healthy, with normal color and texture.

Abnormal hair loss (alopecia) is fundamentally different. It produces visible bald spots, areas of significant thinning, or widespread coat loss that leaves the skin partially or fully exposed. The skin itself may show changes: redness, flaking, darkening, thickening, scabs, bumps, or an oily or foul-smelling quality. Abnormal hair loss is often accompanied by itching, scratching, licking, or chewing, though some causes (like hormonal disorders) produce hair loss without any itching at all.

The distinction matters because normal shedding requires only regular grooming to manage, while abnormal hair loss signals an underlying health problem that needs veterinary attention. If you are unsure whether what you are seeing is normal, a professional groomer can often tell the difference at a glance, as they see hundreds of dogs and their coats every month.

Alopecia in Dogs: What It Means

Alopecia is simply the medical term for hair loss. When your vet says your dog has alopecia, they are describing a symptom, not a diagnosis. The next step is always to determine why the hair loss is happening. Alopecia in dogs can be classified in several ways:

• Focal alopecia: Hair loss in one specific area, such as a single bald patch on the flank or a bare spot on the tail.
• Multifocal alopecia: Multiple bald patches scattered across the body, commonly seen with fungal infections like ringworm.
• Symmetrical alopecia: Hair loss that appears in a mirror-image pattern on both sides of the body, strongly suggestive of a hormonal cause.
• Diffuse alopecia: General thinning of the coat all over the body rather than distinct bald spots.

The type of alopecia your dog has is one of the most important clues your veterinarian uses to narrow down the list of possible causes. This is why your vet will examine the pattern carefully, noting exactly where hair is missing and what the skin looks like in those areas.

Common Causes of Dog Hair Loss

Hair loss in dogs has a long list of potential causes. Here are the most common, organized from the most frequently diagnosed to the less common.

1. Allergies (Environmental and Food)

Allergies are the single most common cause of hair loss in dogs. Environmental allergies (atopic dermatitis) to pollen, dust mites, mold, and grass cause itching that leads to scratching, licking, and chewing, which in turn causes hair loss. The hair loss from allergies is self-inflicted: the dog removes its own hair through constant scratching and licking rather than the hair falling out on its own.

Food allergies can cause similar symptoms. The most common food allergens in dogs are beef, chicken, dairy, wheat, and soy. Dogs with food allergies often have chronic ear infections, itchy paws, and gastrointestinal symptoms in addition to skin issues and hair loss. An elimination diet trial is the gold standard for diagnosing food allergies. Learn more about the connection between diet and coat health in our guide on nutrition and skin allergies.

2. Fleas and Parasites

Flea allergy dermatitis (FAD) is one of the most common skin conditions in dogs worldwide. Dogs with FAD are allergic to proteins in flea saliva, and even a single flea bite can trigger an intense allergic reaction. The resulting itch drives the dog to scratch and chew relentlessly, causing hair loss concentrated over the lower back, tail base, inner thighs, and belly. You may or may not see fleas on your dog, as the allergic dog often grooms them away through all that chewing.

Other parasites that cause hair loss include Demodex mites (demodectic mange), which cause patchy hair loss with or without itching, and Sarcoptes mites (sarcoptic mange or scabies), which cause intense itching and crusty, hairless patches, especially on the ear margins, elbows, and hocks. Cheyletiella mites ("walking dandruff") cause flaky skin and mild hair loss along the back.

3. Bacterial and Fungal Infections

Bacterial skin infections (pyoderma) often develop secondary to another problem like allergies or parasites, but they can also cause hair loss on their own. Bacterial pyoderma produces circular patches of hair loss, redness, pustules (small pus-filled bumps), and crusty or flaky skin. These patches can appear anywhere on the body.

Ringworm (dermatophytosis) is a fungal infection, not a worm, despite its name. It is one of the most recognizable causes of hair loss in dogs because it produces characteristic circular, well-defined bald patches with a scaly or crusty border. Ringworm is contagious to other animals and to humans, so prompt diagnosis and treatment are important. Puppies and immunocompromised dogs are most susceptible.

4. Hormonal Disorders

Hormonal (endocrine) disorders are among the most important causes of hair loss in dogs because they affect the body systemically. The hallmark of hormonal hair loss is that it is typically symmetrical and non-itchy. The dog loses hair evenly on both sides of the body, and the skin may darken or thicken, but the dog does not scratch or seem bothered.

Hypothyroidism (underactive thyroid) is the most common hormonal cause of hair loss in dogs. It typically affects middle-aged dogs and causes symmetrical hair loss on the trunk and tail (the classic "rat tail" appearance), along with weight gain, lethargy, cold intolerance, and skin thickening. Breeds predisposed to hypothyroidism include Golden Retrievers, Doberman Pinschers, Irish Setters, and Dachshunds. If your dog is also showing signs of unexpected weight changes, a thyroid panel is especially important.

Cushing's disease (hyperadrenocorticism) results from chronic overproduction of cortisol. It causes symmetrical hair loss on the trunk, a pot-bellied appearance, increased thirst and urination, increased appetite, muscle weakness, and thin, fragile skin. Cushing's is most common in middle-aged to older dogs and in breeds like Poodles, Dachshunds, and Beagles.

5. Stress and Anxiety

Psychogenic alopecia occurs when a dog compulsively licks, chews, or scratches itself due to stress, anxiety, or boredom. The hair loss is self-inflicted and is most commonly seen on the legs (especially the front legs, a condition called acral lick dermatitis or "lick granuloma"), flanks, and paws. Common triggers include separation anxiety, changes in the household (new baby, new pet, moving), lack of mental stimulation, and confinement. Treatment involves addressing the underlying stress alongside any secondary skin infection that has developed from the constant licking.

Pattern Hair Loss: What Location Tells You

One of the most valuable things you can do before your vet visit is to carefully observe the pattern and location of your dog's hair loss. The pattern is often the single most important diagnostic clue:

Hair loss over the lower back and tail base is classic for flea allergy dermatitis. Hair loss on the face, around the eyes, and on the front legs in a young dog often points to Demodex mites. Hair loss on the paws with staining (a rust-brown discoloration from saliva) indicates chronic licking from allergies. Hair loss on only one area of the body that looks like a hot, moist, angry wound is likely a hot spot. And generalized, whole-body thinning with dry, dull fur and flaky skin can indicate nutritional deficiency or systemic illness.

Regular brushing is one of the best ways to detect early hair loss, skin changes, and parasites before they become serious

Breed-Specific Hair Loss Patterns

Certain breeds are predisposed to specific types of hair loss. Knowing your dog's breed-related risks can help you and your vet reach a diagnosis faster:

• Dachshunds: Prone to color dilution alopecia (in blue or fawn-colored dogs), pattern baldness affecting the ears, and seasonal flank alopecia.
• Bulldogs and Bull Terriers: Susceptible to Demodex mange and skin fold dermatitis that leads to localized hair loss in skin creases.
• Doberman Pinschers: At high risk for color dilution alopecia and hypothyroidism-related hair loss.
• Greyhounds and Whippets: Prone to pattern baldness on the thighs and underside, which is typically cosmetic and does not require treatment.
• Poodles: Susceptible to sebaceous adenitis, an inflammatory condition that destroys the oil-producing glands in the skin, leading to scaling and hair loss.
• Boxers and Bulldogs: Commonly affected by seasonal flank alopecia and are prone to mast cell tumors that can cause localized hair loss.
• Golden Retrievers: Predisposed to hypothyroidism and hot spots, both of which cause hair loss.
• Siberian Huskies: Can develop zinc-responsive dermatosis, causing crusting and hair loss around the face and feet.

Hot Spots and Their Connection to Hair Loss

Hot spots (acute moist dermatitis) are one of the most dramatic-looking causes of hair loss in dogs. They are intensely itchy, moist, red, and often painful lesions that can appear seemingly overnight. A hot spot that was the size of a quarter in the morning can be the size of your palm by evening.

Hot spots develop when something causes the dog to scratch, lick, or chew at one spot intensely enough to break the skin. The warm, moist environment created by the broken skin and saliva allows bacteria to thrive, creating a rapidly spreading infection. Common triggers include flea bites, allergies, ear infections, matted fur trapping moisture, and minor wounds.

Treatment involves clipping the fur around the hot spot to expose it to air, gently cleaning the area, and applying topical or oral antibiotics. An Elizabethan collar (cone) is often necessary to prevent the dog from continuing to lick and chew. Most hot spots heal within 7 to 10 days with proper treatment, and the hair grows back once the skin heals. Matted fur is a major risk factor for hot spots, which is one reason regular professional grooming is so important for coat health.

Seasonal Flank Alopecia

Seasonal flank alopecia (also called cyclic flank alopecia) is a cosmetic condition where dogs develop symmetrical bald patches on their flanks, typically during late fall or winter when daylight hours are shortest. The skin in the affected area often darkens (hyperpigmentation) but is not itchy or painful. The hair usually regrows on its own in spring and summer as daylight increases.

This condition is thought to be related to melatonin levels and the photoperiod (amount of daylight), though the exact mechanism is not fully understood. Breeds most commonly affected include Boxers, Bulldogs, Airedale Terriers, and Schnauzers. While seasonal flank alopecia does not require treatment, some veterinarians recommend melatonin supplementation, which can help prevent recurrence. The main concern is distinguishing seasonal flank alopecia from more serious causes of symmetrical hair loss, like hypothyroidism, which is why a veterinary evaluation is still recommended the first time you notice this pattern.

When to See the Vet

Not all hair loss requires an emergency vet visit, but any unexplained hair loss deserves a professional evaluation. Here are the situations that warrant prompt attention:

How Vets Diagnose Hair Loss

When you bring your dog to the vet for hair loss, your veterinarian will take a systematic approach. The workup starts with a thorough history and physical examination and then proceeds to specific tests based on the findings.

Your vet will ask detailed questions about the timeline (when did the hair loss start?), whether it is getting better or worse, whether your dog is itchy, what preventatives your dog is on (flea, tick, heartworm), dietary history, and any other changes in behavior or health. Taking photographs over time is extremely helpful for your vet to see how the condition is progressing.

Treatment by Cause

Because hair loss is a symptom rather than a disease, treatment depends entirely on addressing the underlying cause. Here is what to expect for the most common diagnoses:

Allergies

For environmental allergies, treatment options include antihistamines, Apoquel (oclacitinib), Cytopoint injections, medicated shampoos, and in some cases immunotherapy (allergy shots or sublingual drops). For food allergies, an elimination diet with a novel protein or hydrolyzed protein food is the standard approach, typically lasting 8 to 12 weeks. Once the offending allergen is identified, avoidance is the best long-term strategy.

Parasites

Flea allergy dermatitis requires rigorous flea control using veterinary-grade products like isoxazolines (Bravecto, NexGard, Simparica). All pets in the household must be treated, and the home environment should be thoroughly cleaned. Demodex mange is treated with isoxazolines or ivermectin, often requiring several months of treatment with follow-up skin scrapings to confirm mite clearance. Sarcoptic mange responds well to isoxazolines or Revolution (selamectin).

Infections

Bacterial pyoderma is treated with antibiotics (oral or topical, depending on severity) and medicated baths. Deep pyoderma may require 6 to 8 weeks of antibiotics. Ringworm is treated with oral antifungal medication (itraconazole or terbinafine), topical antifungal treatments, and environmental decontamination, since fungal spores can persist on surfaces and reinfect the dog. Treatment typically continues until two consecutive negative fungal cultures are obtained.

Hormonal Disorders

Hypothyroidism is treated with daily thyroid hormone supplementation (levothyroxine), which is inexpensive and highly effective. Most dogs show improvement within 4 to 6 weeks, with hair regrowth typically visible within 2 to 3 months. Cushing's disease is more complex to treat and may involve medication (trilostane or mitotane), surgery to remove an adrenal tumor, or radiation for pituitary tumors. Lifelong monitoring is required for both conditions.

Stress-Related Hair Loss

Treatment for psychogenic alopecia involves addressing the root cause of the stress or anxiety. This may include environmental enrichment (puzzle toys, more exercise, training), behavior modification, and in some cases anti-anxiety medication (fluoxetine, trazodone, or clomipramine). Any secondary skin infection from compulsive licking needs to be treated simultaneously with antibiotics. An Elizabethan collar may be necessary during healing.

The Grooming Connection

Professional groomers occupy a unique position when it comes to detecting hair loss in dogs. Because they see and handle your dog's entire body during every appointment, groomers are often the first people to notice early signs of hair loss, skin changes, or coat problems, sometimes before the owner has noticed anything at home.

A skilled groomer may spot a thinning patch on the flank, a circular bald spot hidden under the topcoat, redness or irritation on the belly, or the early stages of a hot spot forming under a mat. They are trained to look at the skin and coat as they work, and because they see your dog regularly, they can notice changes over time that might develop too gradually for you to catch at home.

Beyond detection, proper grooming actively prevents some causes of hair loss. Regular brushing removes loose fur, prevents mats (which trap moisture and create hot spots), distributes natural skin oils, and improves air circulation to the skin. Bathing with appropriate shampoos keeps the skin clean without stripping protective oils. Professional deshedding treatments reduce undercoat buildup that can contribute to skin problems. And routine grooming appointments provide a reliable opportunity for someone knowledgeable about canine skin health to examine your dog from nose to tail.

If your groomer mentions that they noticed a bald patch, thinning, redness, or an unusual skin condition, take it seriously and schedule a vet appointment. Early detection and treatment of hair loss leads to better outcomes for virtually every cause. Finding a great local groomer is one of the best investments you can make in your dog's overall coat and skin health. If your dog is anxious about salon visits, a mobile groomer can provide the same careful attention in the comfort of your home.

Prevention and Coat Health Tips

While you cannot prevent every cause of hair loss, there is a great deal you can do to keep your dog's coat healthy and reduce the risk of many common causes:

Remember that a healthy coat starts from the inside. Good nutrition, proper hydration, parasite control, and low stress levels form the foundation. Regular grooming and veterinary care provide the monitoring and maintenance that keep your dog's skin and coat in top condition.

Frequently Asked Questions

The Bottom Line

Hair loss in dogs is one of the most common reasons owners visit the veterinarian, and for good reason. While normal shedding is just part of life with a dog, true hair loss with bald patches, thinning, or skin changes always signals an underlying problem that needs investigation. The good news is that the vast majority of causes are treatable, and many are completely curable.

Pay close attention to the pattern of your dog's hair loss. Symmetrical hair loss on both sides of the body, especially without itching, points toward hormonal causes that require blood work. Patchy, irregular hair loss with itching, redness, or skin changes suggests infections, parasites, or allergies. And hair loss concentrated over the lower back and tail base is the hallmark of flea allergy dermatitis, which is preventable with consistent flea control.

Early detection makes a significant difference. A small bald patch that is easy to treat today can become a widespread, difficult-to-manage condition if left untreated. Your professional groomer is one of your best allies in catching hair loss early, and regular grooming appointments help prevent several common causes. When in doubt, a vet visit to investigate the cause is always the right call.