Finding a bald spot on your dog is one of those moments that stops you in your tracks. Maybe you noticed it while stroking them — a patch where the skin is suddenly visible through the coat. Maybe it was during brushing, when a whole section came away. Maybe your dog has been licking or scratching a particular spot and now there's a raw, bare area where there used to be fur.
Whatever the pattern, patchy hair loss is different from normal shedding and it's important to understand why. Normal shedding is even — the coat thins generally, especially during seasonal blowout, but no specific area goes noticeably bald. Patches of missing fur almost always mean something specific is happening in that area, or throughout the body, that needs to be identified and addressed.
This guide covers every significant cause of patchy hair loss in dogs — what it looks like, what it means, and what to do about it. Some causes are straightforward and respond quickly to treatment. Some are contagious to other pets and to people in your household. A few are signs of underlying health conditions that need proper investigation. All of them are better caught early.
Quick Answer
Patchy hair loss in dogs is not normal shedding — it almost always indicates an underlying cause. The most common culprits are demodectic or sarcoptic mange, ringworm (fungal infection), allergic skin disease, bacterial skin infection, hormonal conditions like hypothyroidism or Cushing's disease, and stress or anxiety-related over-grooming. A vet visit is the right response to any patchy hair loss — not because it is always serious, but because the cause determines the treatment, and several causes (mange, ringworm) are contagious and need specific intervention.
Table of Contents
- Normal Shedding vs Patchy Hair Loss: The Key Difference
- Where the Patches Are: A Diagnostic Map
- Causes of Patchy Hair Loss in Dogs
- Contagious Causes — What to Watch For
- Hormonal Causes — The Slow and Easy to Miss
- Stress and Anxiety-Related Hair Loss
- What the Skin Underneath Tells You
- Signs That Need a Vet Visit Soon
- What the Vet Will Do
- What You Can Do at Home While You Wait
- FAQs
- Conclusion
- Related Posts
Normal Shedding vs Patchy Hair Loss: The Key Difference
Before anything else — let's make sure we're talking about the same thing. Because the difference between normal heavy shedding and patchy hair loss matters a lot for what comes next.
Normal shedding — even in very heavy shedders — produces an even thinning across the coat. During a seasonal blowout, enormous quantities of undercoat come out, but the coat remains complete. There are no bare patches. No skin visible through specific areas. The coat looks full even as hair is falling.
Patchy hair loss is something different. A specific area — a coin-sized circle, a stripe along the back, a section around the ear, a patch on the flank — has noticeably less hair than the surrounding coat. Or no hair at all. The skin may be visible. The surrounding fur may look normal, or it may look dull, brittle, or broken.
Where the Patches Are: A Diagnostic Map
The location of hair loss patches is one of the most useful clues to the underlying cause before a vet visit. It's not diagnostic on its own, but it narrows the field significantly.
Causes of Patchy Hair Loss in Dogs
Demodectic Mange (Demodex)
Demodex canis is a mite that lives naturally in the hair follicles of virtually all dogs in small numbers, held in check by a healthy immune system. When the immune system is suppressed — through age, illness, stress, or in young puppies whose immune systems are still developing — Demodex populations can overgrow, causing follicular inflammation and hair loss.
Demodectic mange appears in two forms. Localised — small patches of hair loss, typically starting around the face and eyes in puppies, that often resolve on their own as the immune system matures. Generalised — extensive patchy hair loss across large areas of the body, with secondary bacterial infection, that requires active treatment and indicates significant immune compromise.
The skin in affected areas is often reddish, slightly scaly, and may have a moth-eaten appearance. The dog may or may not be itchy — demodectic mange is typically less intensely pruritic than sarcoptic mange. Diagnosis requires a deep skin scrape examined under microscopy to identify the mite. Treatment options include oral isoxazoline medications (the same class used for flea prevention) or medicated dips under veterinary direction.
Important: Demodectic mange is not contagious to other dogs or to humans. It develops from the dog's own resident Demodex population when immunity is compromised.
Sarcoptic Mange (Scabies)
Sarcoptic mange is caused by Sarcoptes scabiei — a mite that burrows into the superficial layers of the skin. Unlike Demodex, Sarcoptes is highly contagious — it spreads through direct contact between dogs and can temporarily infest humans, causing an itchy rash.
Sarcoptic mange causes intense, severe itching — often described as the worst itch in veterinary dermatology. The classic distribution is the ear margins, elbows, hocks, and face — areas with less dense fur where the mites preferentially burrow. The skin in these areas becomes crusty, thickened, and red, and hair loss develops from self-trauma — the dog scratching and biting the affected areas. A dog with sarcoptic mange will be visibly miserable.
Diagnosis is a skin scrape, though Sarcoptes mites are notoriously difficult to find on scrapes — a negative scrape does not rule it out. Many vets treat on clinical suspicion when the presentation is classic. Treatment with isoxazoline medications is highly effective and rapid.
🚨 Contagious to Humans and Other Pets
If you suspect sarcoptic mange — intense itching, crusty ear margins, and elbows in a dog that has been in contact with other dogs — keep affected pets separated from other animals and wash hands thoroughly after handling. Household members who develop an itchy rash should see a doctor and mention the suspected dog diagnosis.
Ringworm (Dermatophytosis)
Despite the name, ringworm is not a worm — it's a fungal infection of the hair shaft and surrounding skin. It is one of the most common causes of circular hair loss patches in dogs and one of the most important to diagnose promptly because it is directly contagious to other animals and to humans.
Ringworm produces circular or irregular scaly patches of hair loss, often with a slightly crusty surface. The classic ring shape — with hair loss in the centre and active infection at the spreading edges — is not always present in dogs. It can look like a dry, flaky bald patch or a broken-haired area without obvious scaling. It is most common in puppies, elderly dogs, and immunocompromised dogs, but any dog can be affected.
Diagnosis by fungal culture (a toothbrush sample cultured for 2–3 weeks) is the most reliable method. Wood's lamp (UV) examination detects some but not all strains. Treatment involves antifungal medication (oral and/or topical) and environmental decontamination — ringworm spores can survive in the environment for months.
🚨 Contagious to People and Other Pets
Ringworm is a zoonotic infection — it passes from dogs to humans readily. Children, elderly people, and immunocompromised individuals are particularly susceptible. If your dog has circular scaly hair loss patches, avoid close face contact until diagnosis is confirmed, wash hands after handling, and do not let affected pets share bedding with family members.
Allergic Skin Disease and Self-Trauma
Dogs with environmental allergies (atopic dermatitis) or food allergies scratch, lick, and chew specific areas of their body intensely. Over time, this self-trauma removes the hair from those areas, leaving patches that look like hair loss but are actually the result of the dog removing it themselves. The skin beneath is often reddened, thickened, or moist from chronic licking.
The giveaway is where the patches appear — in the distribution typical of the allergy type (face, paws, armpits, groin for atopy; similar distribution for food allergy) — and the behaviour driving them. A dog that is observed to lick or scratch a specific area repeatedly until the hair is gone is experiencing itch-driven hair removal, not primary hair loss. Treating the itch resolves the hair loss — the hair grows back when the dog stops removing it.
🔍Related Reading
Dog Itching Remedies: Causes, Home Treatments & When to See a Vet
Bacterial Skin Infection (Pyoderma)
Bacterial skin infection — most commonly Staphylococcal pyoderma — produces characteristic lesions including circular "bull's-eye" patches with a ring of hair loss, crusting, and pigment change. It frequently occurs secondary to another condition that has compromised the skin barrier — allergies, mange, hormonal disease — and both the infection and the underlying trigger need to be treated for resolution.
Superficial pyoderma responds to appropriate antibiotic therapy (guided by culture and sensitivity testing for recurrent cases) alongside medicated shampoo. Deep pyoderma — involving the hair follicle and surrounding tissue — is more severe and requires longer treatment courses.
Flea Allergy Dermatitis
In a dog with flea allergy, a single flea bite triggers an intense, prolonged itching response that can last days or weeks. The dog scratches and chews the affected area — typically the rump, base of tail, and lower back — until the hair is gone and the skin is traumatised. The resulting bare patches can look alarming, but the hair loss is entirely self-inflicted from the itch.
You may not find fleas — an allergic dog grooms them off obsessively but the saliva proteins remain. The absence of visible fleas does not rule out flea allergy. Year-round veterinary-grade flea prevention on all pets in the household is both the treatment and the prevention for this cause.
Alopecia Areata
Alopecia areata is an immune-mediated condition in which the immune system mistakenly attacks the hair follicles, causing focal patches of smooth, clean hair loss — typically on the head, face, or neck — without skin changes. The skin beneath the bald patches looks completely normal. The dog is not itchy. The patches simply appear. It is less common in dogs than in humans but does occur. Some cases resolve spontaneously; others require immunosuppressive treatment.
Seasonal Flank Alopecia
Some dogs — particularly Boxers, English Bulldogs, Airedales, and Dobermanns — develop recurring bilateral (both sides symmetrically) patches of hair loss on the flanks during winter months, as day length shortens. The skin may darken slightly in the affected areas. The coat regrows in spring without treatment. The cause is photoperiodic — related to the hormonal effects of changing day length on hair follicle cycling. Melatonin supplementation can help prevent recurrence in some cases; your vet can advise.
Hormonal Causes — The Slow and Easy to Miss
Hormonal causes of patchy or diffuse hair loss tend to develop slowly — over weeks to months — which means they're often well established by the time a dog parent notices them. The pattern is usually bilateral and symmetrical — matching areas on both sides of the body — and the skin changes that accompany the hair loss tend to be subtle rather than dramatic.
Hypothyroidism
Low thyroid hormone slows every metabolic process including the hair growth cycle. The result is diffuse coat thinning — often most pronounced on the trunk and the pressure points where the dog rests — alongside a dry, dull coat, weight gain without increased appetite, lethargy, and cold intolerance. The skin often thickens and darkens in affected areas. Diagnosis is a simple blood panel including T4 and free T4. Treatment with synthetic thyroid hormone (levothyroxine) produces gradual coat improvement over several months.
Cushing's Disease (Hyperadrenocorticism)
Excess cortisol from Cushing's disease has wide-ranging skin effects — it thins the skin, impairs immune function, and disrupts the hair follicle cycle. The characteristic coat change is bilateral symmetrical trunk hair loss with the head and legs remaining relatively normal, alongside a pot-bellied appearance, increased thirst and urination, and increased appetite. The skin often becomes thin, prone to infection, and may develop calcium deposits (calcinosis cutis). Diagnosis requires specific hormonal testing (LDDST). Treatment with trilostane or mitotane is effective.
Sex Hormone Imbalances
Intact female dogs can develop symmetrical hair loss related to oestrogen changes during false pregnancies, during and after whelping, and at certain stages of the reproductive cycle. Intact males can develop hair loss from testosterone or oestrogen imbalances, sometimes associated with testicular tumours (Sertoli cell tumour classically causes feminisation syndrome with bilateral symmetric alopecia in intact males). Neutering typically resolves hormonally driven hair loss in these cases.
Stress and Anxiety-Related Hair Loss
Stress affects dogs' coats through two pathways that are worth knowing about as a dog parent.
Telogen effluvium — a sudden increase in shed volume, sometimes patchy, that occurs 6–12 weeks after a significant stressor. The trigger could be surgery, illness, pregnancy, whelping, a major life change, or severe psychological stress. The stress event causes a large proportion of hair follicles to synchronise into the telogen (resting and shedding) phase simultaneously. The result is noticeable hair loss that appears weeks after the stressor — which is why the connection is often missed. It usually resolves over several weeks without treatment once the stressor is resolved.
Anxiety-related over-grooming — a dog with generalised anxiety, separation anxiety, or a specific phobia may lick, chew, or scratch specific areas of their body repetitively. Over time this removes the hair from those areas, creating focal patches. Common locations are the paws (the classic "lick granuloma"), the flanks, and the base of the tail. The skin in these areas is often inflamed, thickened, and raw from the chronic trauma. Treating the hair loss without treating the underlying anxiety produces temporary improvement followed by recurrence. A vet or veterinary behaviourist should be involved.
What the Skin Underneath Tells You
While you're waiting for a vet appointment, looking at the skin beneath the patch gives useful information. Here's a quick reference.
Signs That Need a Vet Visit Soon
🚨 Get to the Vet This Week If Your Dog Has:
- Intense scratching, biting, or rubbing at bald patches — particularly if the ear margins, elbows, or hocks are involved (sarcoptic mange)
- Circular scaly bald patches — especially if multiple pets or household members are affected (ringworm)
- Moist, weeping, or broken-skin patches — active infection needs treatment
- Bald patches on a puppy — Demodex in a young dog needs assessment
- Other systemic signs alongside hair loss — increased thirst, weight changes, pot belly, lethargy (hormonal disease)
- Hair loss spreading or worsening over days to weeks — progressive conditions respond better to early treatment
📌 A Note on "Waiting to See"
Patchy hair loss does not resolve on its own without treatment of the underlying cause. Waiting a few weeks to see if it improves almost never changes the outcome for the better — it usually allows the condition to progress, makes diagnosis harder, and in contagious cases (mange, ringworm) gives the condition more time to spread to other pets and people. Early investigation is always better.
What the Vet Will Do
When you bring your dog in for patchy hair loss, the vet will approach it methodically — the history and physical examination already narrow the differential list significantly before any tests are run.
History they'll ask about: When the patches appeared and how they've changed, whether there is itching or other discomfort, what the skin looks like beneath the patches, whether other pets or people in the household are affected, current flea prevention status, recent stressors, diet, and any other symptoms alongside the hair loss.
Examination: Distribution and pattern of hair loss, skin condition in the patches and surrounding areas, lymph node assessment, and general health check.
Tests that help identify the cause:
- Deep skin scrape — for Demodex and Sarcoptes mite identification; examined under microscopy immediately
- Skin cytology (tape strip or impression smear) — for bacteria and yeast; rapid in-clinic result
- Fungal culture (toothbrush technique) — for ringworm diagnosis; takes 2–3 weeks for definitive result but treatment may begin while awaiting results
- Wood's lamp examination — screens for ringworm strains that fluoresce; does not detect all strains
- Full blood panel including thyroid function — for hormonal causes; T4, free T4, LDDST or urine cortisol:creatinine for Cushing's
- Skin biopsy — for complex or treatment-resistant cases; confirms the histological pattern of hair loss and may identify the specific cause
- Trichoscopy (hair microscopy) — examining plucked hairs microscopically; identifies whether hair loss is at the follicle level or due to shaft breakage (distinguishing self-trauma from primary hair loss)
What You Can Do at Home While You Wait
If you've noticed patchy hair loss and have a vet appointment booked — great. Here's what to do (and not do) in the meantime.
Don't apply anything to the patches. Resist the urge to put coconut oil, tea tree oil, or any home remedy on the affected areas until you know what you're dealing with. Some causes (open skin infection, sarcoptic mange) can be worsened by topical applications. Tea tree oil is toxic to dogs and should never be used. If the patches are clearly moist or weeping, an e-collar (cone) prevents further self-trauma while you wait for the appointment.
Do note and photograph. Take clear photos of the patches — close-up showing the skin beneath, and wider shots showing the location on the body. Note when you first noticed them, whether they've changed size or number, and any symptoms your dog is showing (itching, licking, changed behaviour). This information is gold for your vet.
Continue fish oil supplementation if your dog is already on it — omega-3 supports skin health generally and won't interfere with diagnosis. If they're not on it, starting now supports the skin barrier regardless of the eventual diagnosis.
Keep affected pets separated if you have multiple animals, until the cause is confirmed. Sarcoptic mange and ringworm spread quickly between pets in close contact.
Keep the affected areas clean and dry — not medicated, just clean. A warm water rinse of any moist or weeping areas followed by gentle air drying keeps secondary infection from worsening while you wait.
Frequently Asked Questions
Why is my dog losing fur in patches?
Patchy hair loss is almost always caused by an underlying condition — demodectic or sarcoptic mange, ringworm, allergic skin disease with self-trauma, bacterial skin infection, flea allergy, or hormonal disease (hypothyroidism, Cushing's, sex hormone imbalance). The location of the patches, the skin beneath them, and whether there's itching involved all point toward the likely cause. A vet visit is the right next step — patchy hair loss doesn't resolve without treating the underlying cause.
Is patchy dog shedding normal?
No. Normal shedding thins the coat evenly — no specific area goes bare. Patches of missing fur are a sign of an underlying condition and should be investigated. The sooner the cause is identified, the better the outcome — some causes (mange, ringworm) are contagious to other pets and people and need to be caught and treated early.
What causes circular patches of hair loss in dogs?
Ringworm (fungal infection) is the classic cause of circular bald patches — scaly, with active infection at the spreading edges. Demodectic mange causes focal patches often starting around the face. Bacterial pyoderma produces bull's-eye lesions. All three need veterinary diagnosis before treatment — the approach is different for each and using the wrong treatment for the wrong condition delays resolution.
Can stress cause a dog to lose fur in patches?
Yes — two ways. Telogen effluvium occurs 6–12 weeks after significant stress as hair follicles synchronise into the shedding phase simultaneously. Anxiety-related over-grooming causes focal hair loss in areas the dog licks or chews compulsively. Both are real, both are manageable, and both need the underlying stress or anxiety addressed rather than just the hair loss treated symptomatically.
Should I take my dog to the vet for patchy hair loss?
Yes, always. Patchy hair loss is not a grooming problem or a normal variation — it needs diagnosis. Some causes are contagious (mange, ringworm). Others indicate hormonal disease that benefits significantly from early treatment. And unlike normal shedding, patchy hair loss will not resolve on its own without addressing what's causing it.
Conclusion
Noticing a bald patch on your dog is unsettling — and the instinct to worry is the right one here. Patchy hair loss is genuinely different from normal shedding, and it genuinely does need attention. The good news is that most causes of patchy hair loss in dogs are very treatable, especially when caught early. Mange responds quickly to modern parasiticides. Ringworm clears with antifungal treatment. Hormonal conditions managed correctly allow the coat to recover over months. Allergy-related self-trauma resolves when the itch is brought under control.
The thing that makes the biggest difference between a quick resolution and a prolonged one is how soon the cause is identified. A vet appointment, a few diagnostic tests, and a confirmed diagnosis means a targeted treatment that actually works — rather than weeks of trying things and waiting for patches to improve on their own.
Your dog is relying on you to notice these things. And you did. That's exactly what a good dog parent does.
Have you dealt with patchy hair loss in your dog before? What turned out to be the cause? Drop it in the comments — your experience might help another dog parent who's staring at a bald patch right now and wondering what to do.
Related Posts
- Dog Itching Remedies: Causes, Home Treatments & When to See a Vet — When the hair loss is driven by itching and scratching — the full guide to allergic skin disease and what actually helps.
- Dog Dandruff Treatment at Home — Flaking skin alongside patchy hair loss can indicate seborrhoeic conditions, mange, or ringworm — this guide covers the skin changes that often accompany hair loss.
- How to Reduce Dog Shedding Fast — For normal shedding (not patchy) — the tools, habits, and diet changes that make a real difference.
- Why Does My Dog Pant at Night? — Hypothyroidism and Cushing's disease cause both patchy hair loss and nocturnal panting — if your dog has both, the hormonal angle is worth investigating.
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