Why Is My Dog Losing Hair? Causes of Patches, Thinning and Bald Spots

Finding a thin patch or bald area in your dog’s coat can mean something very different from noticing loose fur on a brush. Abnormal hair loss, medically called alopecia, can develop when hair follicles are damaged, hair growth slows, or a dog scratches, chews or licks hair away.

If you are wondering why is my dog losing hair, the location and pattern can provide useful clues, but they cannot diagnose the cause. Parasites, allergies, skin infections, hormonal problems, repeated licking and several other conditions can look similar. Veterinary examination and tests such as skin scrapings, cytology, fungal testing or blood work may be needed.

Direct Answer

Hair loss in dogs can be associated with parasites, allergies, bacterial or fungal skin disease, repeated licking, friction, hormonal disorders, nutritional problems and other conditions. Itching, redness, crusts, odour, symmetrical thinning and the location of bald areas can help guide investigation, but the pattern alone cannot identify the cause.

Normal Shedding Versus Abnormal Hair Loss

Normal shedding is part of the hair-growth cycle. Old hairs are naturally released as the coat renews itself, and the amount can vary with breed, coat type, season and environment.

Hair loss becomes more concerning when you can see:

• distinct bald spots
• clearly thinning areas
• patchy loss
• symmetrical areas with much less hair
• redness
• crusting
• scaling
• sores
• repeated licking or scratching

Merck notes that shedding without bald patches or symmetrical hair loss is more likely to represent natural coat replacement, whereas obvious coat loss or areas of alopecia deserve further attention.

This article is focused on abnormal hair loss. For ordinary seasonal shedding and ways to manage loose fur, link readers to Pawnium’s existing Reduce Dog Shedding article rather than duplicating that topic here.

Hair Loss With Itching

Dog hair loss and itching often occur together because repeated scratching, biting, rubbing or licking physically damages the coat.

Common categories veterinarians consider include:

• fleas
• mites
• allergic skin disease
• bacterial infection
• fungal infection

Merck identifies parasites, infections and allergies as major causes of itching in dogs. Itchy dogs may repeatedly scratch, bite or lick, eventually producing broken hairs and areas of alopecia.

If your dog is intensely itchy but you cannot see fleas, Pawnium’s Why Is My Dog Itching Without Fleas? article is a useful next internal link.

Hair Loss Without Itching

Dog hair loss without itching requires a different line of investigation.

Non-itchy alopecia can occur when something interferes with normal hair growth rather than causing the dog to scratch hair away. Merck lists hormonal imbalances and certain nutritional deficiencies among causes that can inhibit or slow hair-follicle growth.

Endocrine disorders can sometimes produce symmetrical, non-itchy thinning, although secondary skin infection may later introduce itching.

A dog with painless-looking symmetrical loss still needs proper evaluation. Absence of itching does not identify an endocrine problem by itself.

Fleas

Fleas can cause hair loss directly through scratching and, in susceptible dogs, through flea-allergy dermatitis.

Dogs with flea allergy may intensely:

• scratch
• chew
• rub
• lick
• bite at the skin

The lower back, hips, thighs and base of the tail are characteristic areas where flea-allergy dermatitis may cause crusting, itching and hair loss.

Not seeing a flea does not completely exclude flea-related disease. Veterinary investigation may consider flea exposure and prevention history as well as the distribution of the skin lesions.

Link this section to Pawnium’s Flea-Prevention Guide.

Mites

Several mites can cause canine skin disease, but different mite problems do not all look the same.

Sarcoptic mange can cause marked itching, inflammation, crusting and hair loss. Demodicosis may produce focal or widespread areas of alopecia, redness and scaling; some localised cases have little or no itching.

Veterinarians may use skin scrapings or hair samples to investigate mites. Appearance alone cannot confirm which parasite is involved.

Do not diagnose “mange” simply because a dog has bald patches.

Skin Infections

Bacterial and fungal skin infections can damage follicles and contribute to hair loss.

Superficial bacterial pyoderma may cause:

• small bald patches
• scaling
• scabs or crusts
• redness
• bumps or pustules

Deeper infections can also cause pain, odour, swelling and discharge.

Fungal dermatophytosis, commonly called ringworm, can cause hair loss with scaling, crusting, redness and variable itching. Laboratory testing of hairs or skin scales is commonly used to confirm it.

Do not identify a bacterial, yeast or fungal infection solely from how a bald patch looks or smells.

Allergies

Allergic skin disease commonly causes itching rather than hair simply falling out on its own.

Dogs may:

• scratch
• chew their paws
• rub their faces
• lick itchy areas
• develop secondary skin or ear infections

Over time, scratching and licking can produce hair loss, red skin and thickened or darker skin.

Environmental allergies, food-related allergy and flea allergy can overlap in appearance, which is why location alone cannot identify the allergen.

Useful Pawnium internal links here include:

• Why Is My Dog Itching Without Fleas?
• Dog Paw Licking
• Itchy-Skin Shampoo Guide

Excessive Licking

Persistent licking can physically remove or break hairs.

The key question is why the dog is licking.

Possible triggers can include:

• itching
• allergy
• infection
• parasites
• local pain
• inflammation
• behavioural factors

Cornell notes that allergic dogs commonly lick and chew their feet, which can eventually produce visible hair loss.

Repeated licking of one particular area can also develop into acral lick dermatitis. VCA notes that this condition may have medical, behavioural or combined causes, so it should not automatically be labelled anxiety.

Friction and Pressure

Repeated rubbing can wear hair away.

Merck specifically notes that friction from poorly fitted equipment such as collars can cause localised alopecia.

Pressure points such as elbows and hocks can also develop skin problems because of repeated contact and trauma, particularly if inflammation or infection develops.

Check whether a bald patch corresponds with:

• a collar
• harness straps
• clothing
• repeated contact with bedding or flooring
• another obvious pressure area

If the skin itself is inflamed, crusted or painful, the problem should not simply be dismissed as cosmetic rubbing.

Hormonal or Endocrine Problems

Hormonal disorders are important possible causes of non-inflammatory hair thinning.

For example, hypothyroidism can be associated with delayed hair regrowth, excessive shedding and non-itchy hair thinning that is often bilaterally symmetrical.

Hyperadrenocorticism, or Cushing syndrome, can also cause alopecia and other skin changes. A typical endocrine pattern may be symmetrical across the trunk, but the hair-loss pattern by itself cannot diagnose either condition.

Veterinarians consider the dog’s complete health picture and may use blood, urine and hormone-related testing when an endocrine problem is suspected.

Nutritional Problems

Skin and coat health depend on adequate nutrition.

Deficiencies involving protein, fats, minerals, vitamins or trace elements can contribute to skin and coat abnormalities. However, Merck notes that nutritional deficiency is uncommon in dogs eating modern, balanced diets.

Do not respond to unexplained hair loss by randomly adding:

• zinc
• vitamins
• oils
• protein supplements
• skin supplements

without first considering the dog’s complete diet and veterinary assessment.

Too much supplementation can create other problems, and the correct treatment depends on whether a nutritional deficiency actually exists.

Medication Effects

Some medications and medical treatments can affect the coat.

Long-term glucocorticoid use can cause changes associated with iatrogenic Cushing syndrome, including bilaterally symmetrical alopecia.

Certain chemotherapy protocols can also affect rapidly dividing hair follicles. AAHA notes that hair loss is more noticeable in some continuously growing coat types.

Do not stop a prescribed medicine because hair loss develops. Record when the change started and discuss it with the prescribing veterinarian.

Stress

Stress is sometimes blamed for unexplained bald spots, but it should not become the default diagnosis after medical causes have not yet been investigated.

Some dogs develop repetitive licking or chewing behaviours that can damage the skin and coat. VCA notes that chronic stress or emotional conflict may contribute to compulsive licking in certain dogs, but medical causes such as pain and dermatological disease must also be considered.

A behavioural explanation should therefore usually come after appropriate medical investigation, not before it.

Hair Loss After Grooming

If hair loss appears after grooming, first record exactly where the coat was clipped, brushed or treated and when the problem began.

Some heavily coated dogs can develop delayed hair regrowth after clipping, sometimes called post-clipping alopecia. VCA describes it as an uncommon problem that occurs particularly in some plush-coated breeds.

A different issue is inflammation after grooming. Deep pyoderma can occasionally develop in association with grooming and may cause painful skin lesions rather than simple delayed coat regrowth.

If there is:

• redness
• swelling
• pain
• discharge
• crusting
• rapidly spreading lesions

contact your veterinarian rather than assuming the hair was simply cut too short.

For routine coat maintenance, link readers to Pawnium’s Dog Grooming Schedule.

Seasonal Coat Changes

Seasonal shedding can produce impressive amounts of loose hair without causing true bald areas.

AAHA notes that shedding is a normal part of the hair-growth cycle and can vary with breed, season and environment.

The distinction is important:

Loose hair throughout an otherwise normal coat may represent shedding.

Visible patches, thinning or exposed skin are more consistent with abnormal hair loss and deserve closer attention.

Detailed tips for reducing loose hair should remain in Pawnium’s existing Reduce Dog Shedding article.

Circular Bald Spots

Circular or well-defined bald spots often make owners immediately think of ringworm.

Ringworm can produce areas of hair loss, scaling, crusting and redness. However, those findings overlap with other problems, including demodicosis and bacterial follicular disease.

Merck describes fungal culture, direct examination of hair or scales and other dermatophyte testing as methods used to diagnose ringworm.

Therefore:

Circular bald spot ≠ confirmed ringworm.

Have persistent or spreading circular lesions evaluated instead of treating based on shape alone.

Symmetrical Hair Loss

Symmetrical hair loss means a similar pattern appears on both sides of the body.

This pattern can occur with some endocrine and inherited hair disorders. Hypothyroidism, for example, may cause bilateral symmetrical thinning, and Cushing syndrome can produce symmetrical alopecia of the trunk.

But symmetry is a pattern, not a diagnosis.

A veterinarian may consider:

• whether the dog itches
• general energy level
• weight changes
• drinking and urination
• skin thickness
• pigmentation
• recurrent infections
• medication history

before deciding which tests are appropriate.

Hair Loss Around the Eyes

Hair loss around the eyes has several possible explanations.

Localised demodicosis in young dogs commonly affects well-defined areas around the lips, eyes and forelimbs and may have little itching.

Other possibilities include:

• allergic rubbing
• skin infection
• fungal disease
• repeated scratching
• local irritation

Allergic dogs commonly rub their faces and eyes, which can contribute to hair damage.

Do not apply skin products close to the eye without veterinary guidance.

If the eye itself is red, painful, squinting or producing abnormal discharge, an eye examination may also be needed.

Hair Loss Around the Tail

Hair thinning or bald areas around the base of the tail are particularly useful to photograph because distribution can help a veterinarian narrow the possibilities.

Flea-allergy dermatitis commonly affects the tailhead, lower back and caudal thighs and can cause marked itching, crusting and self-induced hair loss.

However, not every bald tail area is caused by fleas. Endocrine disease and other dermatological conditions can also affect the tail or surrounding coat.

Use the location as a clue, not a diagnosis.

Hair Loss on Paws

Dogs often lose paw hair because they repeatedly lick or chew their feet.

Allergic skin disease commonly involves the feet, and continual licking can cause hair loss and saliva staining.

Paw inflammation can also involve:

• infection
• mites
• foreign material
• deeper interdigital disease

Pododermatitis can cause red or swollen paws, hair loss, lesions and persistent licking.

Pawnium’s Dog Paw Licking article should handle the detailed causes of paw-focused licking.

Hair Loss With Redness

Redness indicates skin inflammation but does not tell you why the skin is inflamed.

Dermatitis can occur with:

• allergies
• parasites
• infection
• irritants
• trauma
• other skin disease

Merck notes that dermatitis may appear with itching, redness, scaling, odour and hair loss.

Hair loss with marked redness is more concerning than coat thinning over otherwise normal-looking skin and generally deserves veterinary assessment.

Hair Loss With Crusting

Crusting can occur with several skin disorders.

Examples include:

• bacterial pyoderma
• dermatophytosis
• mite infestation
• chronic self-trauma

Superficial pyoderma commonly causes alopecia together with crusts and scales, while dermatophytosis and demodicosis can produce overlapping patterns.

Do not pick off crusts aggressively or diagnose the condition based on photographs alone.

Hair Loss With Odour

A noticeable skin odour can be associated with inflammation or secondary infection.

Merck notes that bacterial and fungal infections may accompany hair loss with scaling, odour and discharge. Deep pyoderma can also cause pronounced odour along with pain, crusting and secretions.

Smell cannot reliably distinguish bacteria from yeast.

If the hair loss is accompanied by a strong new odour, greasy skin, discharge, redness or pain, arrange veterinary evaluation.

Hair Loss in Puppies

Puppies can develop several causes of alopecia that differ in importance and management.

Localised demodicosis is commonly seen in dogs under one year of age and can create several small red, scaly, hairless areas with little or no itching.

Dermatophytosis can also occur in puppies and may cause multiple areas of hair loss, scaling and crusting.

These conditions can look similar, so testing may be required.

A puppy with rapidly spreading skin disease, widespread inflammation, lethargy, fever or poor overall condition should receive veterinary attention promptly.

Hair Loss in Senior Dogs

New hair loss in an older dog deserves attention because skin changes can sometimes accompany broader health problems.

AAHA’s senior-care guidelines recommend documenting alopecia and other skin lesions and considering baseline dermatology diagnostics such as skin scraping, cytology and fungal testing when appropriate. Broader laboratory evaluation may also be relevant depending on the dog’s overall condition.

Endocrine diseases such as hypothyroidism and Cushing syndrome also occur more commonly in adult and older dogs than in puppies.

Do not simply attribute new coat thinning to “old age.”

What Owners Should Photograph

Good photographs help show whether a lesion is expanding, changing colour or developing additional inflammation.

Take photographs of:

1. The whole dog from above
2. Both sides of the body
3. The exact bald or thinning area
4. The same area from a consistent distance
5. Redness, crusting or scales
6. The tail base if affected
7. Each paw if there is licking
8. Areas around the eyes or face
9. Any new lesions as they appear

Include a date with each photograph.

Also record whether the area is:

• symmetrical
• itchy
• painful
• red
• smelly
• scaly
• crusted
• being repeatedly licked

Photographs are most helpful for showing progression; they cannot replace skin testing or physical examination when a diagnosis is needed.

Why Home Diagnosis Is Unreliable

Hair-loss patterns overlap considerably.

A round patch might be associated with:

• dermatophytosis
• demodicosis
• bacterial follicular disease
• trauma

An itchy patch could involve:

• fleas
• mites
• allergies
• infection

Symmetrical non-itchy thinning might raise concern for an endocrine disorder, but even that pattern does not establish which disease is present.

Veterinary investigation may include:

• flea combing
• skin scraping
• hair examination
• cytology
• bacterial culture
• fungal testing
• skin biopsy
• blood or urine testing

depending on the pattern and the dog’s other symptoms.

Treating the appearance without identifying the cause can delay appropriate care.

When Veterinary Evaluation Is Needed

Arrange a veterinary examination if your dog develops:

• definite bald patches
• progressive coat thinning
• hair loss that keeps spreading
• significant itching
• repeated chewing or licking
• redness
• crusting or scaling
• strong skin odour
• pus or other discharge
• painful skin
• symmetrical hair loss
• delayed hair regrowth without an obvious explanation
• recurring skin infections
• paw inflammation
• widespread lesions
• new hair loss accompanied by other changes in health

Merck emphasises that alopecia is a sign and that successful treatment depends on identifying the underlying cause.

Seek veterinary care more promptly if your dog also develops:

• marked lethargy
• fever
• rapidly spreading painful skin disease
• substantial swelling
• draining lesions
• significant appetite changes
• other signs of systemic illness

Severe mite disease and deep bacterial infections can be accompanied by systemic illness and require professional treatment.

FAQs

Why is my dog losing hair in patches?

Patchy hair loss can occur with parasites, bacterial or fungal infections, allergies, self-trauma, friction and other skin disorders. Because several conditions create similar bald patches, veterinary skin testing may be needed to identify the cause.

Why is my dog losing hair but not itching?

Non-itchy hair loss can occur with conditions that interfere with hair growth, including some hormonal disorders and nutritional problems. Symmetrical non-itchy thinning can occur with endocrine disease, but the pattern alone is not diagnostic.

Does a circular bald spot mean my dog has ringworm?

No. Ringworm can produce bald, scaly or crusted patches, but demodicosis and bacterial skin disease can look similar. Fungal testing may be needed to confirm dermatophytosis.

Why is my dog losing hair around the tail?

Flea-allergy dermatitis commonly affects the tail base and can cause itching, crusting and hair loss. Other skin and hormonal disorders can affect this region too, so the location alone cannot confirm fleas.

Can allergies cause bald spots in dogs?

Yes. Allergies commonly cause itching, licking and chewing, which can damage hair and create thinning or bald areas. Secondary skin infections can make the hair loss more noticeable.

Can stress make a dog lose hair?

Behavioural licking associated with stress or emotional conflict can contribute to self-trauma in some dogs, but medical causes such as allergy, infection, parasites and pain should be investigated before assuming the problem is behavioural.