Dog Hair Loss and Thinning: Causes, Warning Signs & What to Do

Dog hair loss can be easy to miss at first.

You may notice more hair on the couch, a thinner patch around the neck or tail, a widening bald spot, broken hairs, or areas where the coat simply does not look as full as it used to. Sometimes the skin looks completely normal. Other times there may be redness, itching, flakes, odor, scabs, or sores.

Hair loss in dogs is called alopecia. It is not one single disease. It is a sign that something is affecting the hair, skin, hair follicles, or the dog’s overall health. Merck Veterinary Manual notes that hair loss can have many causes, including infections, parasites, allergies, hormonal problems, nutritional deficiencies, trauma, and hereditary conditions. (Merck Veterinary Manual)

This guide explains the difference between normal shedding and true hair loss, common causes of thinning coats, what you can safely check at home, and when it is time to call a veterinarian.

Quick Answer: Why Is My Dog Losing Hair?

Dog hair loss and thinning can happen for many reasons.

Common possibilities include:

normal shedding
fleas, mites, or lice
bacterial or fungal skin infections
allergies
repeated licking or chewing
friction from collars or harnesses
hormonal conditions
poor nutrition
hereditary coat disorders
pregnancy, nursing, or recovery after illness
skin inflammation
certain medications
less commonly, immune disease or cancer

The most important question is not simply, “Why is my dog shedding?”

It is:

Is this normal shedding, or is the coat actually becoming thin or bald?

If your dog has bald patches, skin irritation, scabs, wounds, odor, pain, severe itching, or progressive thinning, contact a veterinarian.

Normal Shedding vs Hair Loss

Dogs naturally shed old hair as new hair grows.

Some dogs shed seasonally. Others shed fairly evenly throughout the year, especially dogs that live mostly indoors. The ASPCA notes that regular shedding is normal, while excessive hair loss or bald patches can be associated with parasites, infections, allergies, internal disease, medication effects, licking, and other health problems. (ASPCA)

Normal shedding usually looks like:

loose hair coming out during brushing
more hair during seasonal coat changes
no obvious bald spots
no red or painful skin
no strong odor
no major change in the overall coat pattern

Abnormal hair loss may look like:

bald patches
widening thin spots
symmetrical thinning
broken hairs
hair coming out in clumps
hair loss around the tail, face, ears, legs, or belly
skin color changes
scaling or flakes
redness or inflammation
constant licking or scratching

If the coat is visibly disappearing rather than simply shedding, it deserves a closer look.

Suggested In-Article Image: Normal Shedding vs Hair Loss

A useful image here would show a simple side-by-side comparison:

Normal shedding: healthy full coat with loose hairs on a brush
Possible hair loss: visible thinning or a small bald patch

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Comparison of normal dog shedding and visible coat thinning or hair loss.

Common Causes of Dog Hair Loss and Thinning

There are many possible causes, which is why guessing based on appearance alone can be difficult.

Fleas, Mites, and Other Parasites

Parasites are a common cause of itching and hair loss.

Fleas can trigger intense itching in sensitive dogs, especially around the tail base and lower back. Mites can cause patchy hair loss, itching, inflammation, or crusting depending on the type.

Dogs may lose hair because the parasite affects the skin directly or because the dog scratches, bites, or licks the area repeatedly.

Look for:

scratching
chewing
flea dirt
scabs
red skin
patchy thinning
crusting
hair loss around the tail or hindquarters

A veterinarian may need to perform skin scrapings or other tests to identify mites or other parasites.

Allergies

Allergies can cause significant coat thinning because the dog keeps scratching, licking, chewing, or rubbing irritated skin.

Possible signs include:

paw licking
face rubbing
ear problems
belly redness
itching
recurring skin infections
hair thinning where the dog licks
hot spots
darkened skin over time

Allergies may involve environmental triggers, fleas, food, or contact irritation.

Hair loss caused by allergies is often secondary to the itching rather than the hair simply falling out on its own.

Bacterial, Fungal, or Yeast Infections

Skin infections can damage hair follicles and cause hair loss.

Merck notes that bacterial and fungal infections are among the diseases that can directly damage hair shafts or follicles. (Merck Veterinary Manual)

Signs may include:

red skin
circular hair-loss patches
odor
greasy skin
crusts
pustules
scabs
flakes
sores
itching

Some infections require prescription treatment, so do not rely on grooming products alone if the skin looks infected.

Excessive Licking or Chewing

Dogs can remove their own hair by repeatedly licking, biting, or scratching.

The trigger might be:

allergies
pain
fleas
skin irritation
anxiety
infection
a wound
joint discomfort underneath the area

Hair may look broken or very short rather than completely absent.

If one spot is constantly wet from licking, find out why the dog is focused on that area.

Collar or Harness Friction

Friction can cause localized thinning.

Merck specifically notes that poorly fitted collars can cause local hair loss. (Merck Veterinary Manual)

Check for thinning:

around the neck
under harness straps
behind the front legs
around the chest
anywhere clothing or equipment rubs repeatedly

Make sure collars and harnesses fit properly and are not left damp against the skin.

If the area is raw or irritated, stop using the equipment until the skin is checked.

Hormonal Conditions

Hormonal problems can cause coat thinning, sometimes without much itching.

Merck lists hormonal imbalances such as hypothyroidism and hyperadrenocorticism, commonly called Cushing’s disease, among conditions that can slow hair growth. (Merck Veterinary Manual)

Hormonal hair loss may appear:

symmetrical
along both sides of the body
around the trunk
in areas of friction
with changes in skin pigmentation

Other signs may be present too, such as changes in weight, thirst, urination, energy, or body shape.

These conditions require veterinary testing.

Nutrition Problems

A balanced diet supports healthy skin and hair growth.

Severe nutritional deficiencies can contribute to poor coat quality and hair loss. Merck identifies protein deficiency among nutritional problems that can inhibit normal hair follicle growth. (Merck Veterinary Manual)

That does not mean every dog with thinning hair needs supplements.

Random supplements can be unnecessary or inappropriate. If you suspect a diet problem, talk with your veterinarian before adding oils, vitamins, or changing food repeatedly.

Hereditary Hair Loss

Some dogs inherit conditions that affect hair growth.

Merck describes several hereditary or congenital alopecia conditions, including color dilution alopecia, follicular disorders, seasonal flank alopecia, and other breed-associated patterns. (Merck Veterinary Manual)

Inherited hair loss may appear:

early in life
in a predictable pattern
symmetrically
without much itching
in certain coat colors or breeds

A veterinarian may need to rule out more common causes before concluding that hair loss is hereditary.

Hair Loss After Illness or Major Stress on the Body

Some dogs temporarily shed more hair after pregnancy, nursing, fever, or significant illness.

Merck notes that temporary hair loss can occur several weeks after severe illness or fever and during pregnancy or lactation. (Merck Veterinary Manual)

If the dog otherwise seems well and the skin looks normal, coat growth may eventually return.

Still, unexplained thinning should be discussed with a veterinarian, especially if it progresses.

What Does the Pattern of Hair Loss Tell You?

The location and pattern can give your veterinarian useful clues.

One small bald patch

This could involve trauma, infection, parasites, licking, friction, or another local skin problem.

Several scattered patches

Possible causes include skin infection, mites, allergies, or inflammatory skin disease.

Symmetrical thinning

Hair loss that looks similar on both sides may raise questions about hormonal or hereditary causes.

Hair loss with severe itching

Allergies, parasites, and infection become particularly important possibilities.

Hair loss without itching

Hormonal, hereditary, or other non-inflammatory causes may need consideration.

These patterns are clues, not a diagnosis.

Warning Signs: When to Call a Veterinarian

Contact a veterinarian if hair loss is accompanied by:

open sores
bleeding
pus or discharge
strong odor
swelling
severe itching
constant licking or chewing
scabs
painful skin
greasy or very flaky skin
sudden bald patches
rapidly spreading hair loss
darkened or thickened skin
weight changes
increased thirst or urination
low energy
changes in appetite
repeated ear infections
hair loss that keeps returning

The ASPCA specifically recommends veterinary attention for bald spots or thinning coats, skin irritation, open sores, dull dry hair that pulls out easily, scratching, and persistent licking or face rubbing. (ASPCA)

What You Can Check at Home

Before your appointment, take a careful look.

Ask yourself:

When did the thinning begin?
Is it getting worse?
Is the dog itchy?
Is the skin red?
Is there odor?
Are there flakes or scabs?
Is the hair broken or falling from the root?
Is the pattern symmetrical?
Has food changed?
Has shampoo changed?
Is the dog taking new medication?
Does a collar or harness rub that spot?
Has the dog been licking excessively?
Are fleas visible?
Has your dog recently been sick?

Take photos every few days if the change is gradual.

That can make progression easier to see.

Suggested In-Article Image: Dog Hair Loss Warning Signs

A second image could show a calm dog with several non-graphic callouts:

thinning coat
itching
redness
bald patch
excessive licking

Recommended image file name:

dog-hair-loss-warning-signs.png

Recommended alt text:

Dog with callouts showing common hair-loss warning signs such as thinning coat, itching, redness, and excessive licking.

Should You Brush a Dog With Thinning Hair?

Usually, gentle grooming is fine if the skin is healthy and not painful.

Use a soft, coat-appropriate tool and light pressure.

Do not aggressively brush an area that is:

red
raw
crusted
swollen
bleeding
painful
infected-looking

If hair is falling out easily or the skin is abnormal, stop trying to groom the problem away.

Brushing helps maintain a coat. It does not treat the underlying cause of alopecia.

Use the Dog Brush and Comb Finder if you need help choosing a gentler tool.

Should You Bathe a Dog With Hair Loss?

That depends on why the hair is falling out.

A normal bath may be fine for a healthy dog with mild shedding. But if the skin is irritated, infected, raw, very dry, or extremely itchy, ask your veterinarian before changing shampoos or bathing more often.

Avoid:

human shampoo
essential oils
harsh degreasers
random antifungal products
repeated bathing to stop shedding
medicated products without knowing what condition you are treating

A veterinarian may prescribe a specific shampoo when infection, yeast, or another skin condition is involved.

Can Grooming Cause Hair Loss?

Sometimes.

Overly aggressive grooming can break hair or irritate skin.

Potential problems include:

brushing too hard
using a deshedding tool excessively
repeatedly scraping the same area
clipper irritation
tight rubber bands
pulling tangled hair
friction from grooming equipment

Grooming should leave the skin comfortable, not red or sore.

If thinning started immediately after a grooming session and the skin looks irritated, contact the groomer and monitor the area.

Call your veterinarian if the skin is painful, injured, swollen, or worsening.

What Will a Veterinarian Check?

Because so many conditions can cause hair loss, diagnosis often takes more than looking at the coat.

Merck explains that veterinarians may evaluate the distribution of hair loss, look for parasites or secondary skin infections, examine whether hairs are shedding or breaking, and perform tests such as skin scrapings, cultures, bloodwork, or biopsies when needed. (Merck Veterinary Manual)

Your veterinarian may ask about:

when the problem started
whether the dog is itchy
diet
medication
flea prevention
previous skin problems
other health changes
breed and age
grooming routine

Treatment depends entirely on the cause.

There is no single “hair loss treatment” that works for every dog.

Will My Dog’s Hair Grow Back?

Often, yes — but it depends on the cause.

Hair may grow back after:

parasites are treated
infection clears
allergies are controlled
rubbing stops
excessive licking stops
the underlying illness improves

Some hereditary conditions or diseases that permanently damage hair follicles may result in incomplete regrowth.

Coat recovery also takes time. Skin may improve before the hair becomes full again.

What About Supplements for Dog Hair Growth?

Be careful with products promising fast coat regrowth.

Hair loss should be understood before supplements are added.

If your dog already eats a nutritionally complete diet, adding large amounts of vitamins, oils, or minerals may not solve the problem and could sometimes create new problems.

Ask your veterinarian whether nutrition is actually contributing to the hair loss before buying supplements.

Hair Loss and Dandruff Together

Thinning hair combined with flakes can point toward a skin problem rather than ordinary shedding.

Possible causes may include:

seborrhea
infection
allergies
parasites
dry or irritated skin
excessive licking

If your dog has both symptoms, read Dog Dandruff and Flaky Skin.

Pay particular attention to odor, itching, redness, and greasy or crusty skin.

Hair Loss Under Mats

Matted hair can hide skin damage.

Once a mat is removed, you may find:

thinning
broken hair
redness
sores
irritated skin
infection
areas where hair has been pulled tightly

Do not assume the grooming process caused every bald area that becomes visible afterward. Sometimes the underlying skin had already been damaged beneath the mat.

If you find open wounds, read Wounds From Matting in Dogs and contact a veterinarian.

When a Professional Groomer Can Help

A professional groomer can help you maintain the remaining coat and identify areas that deserve closer attention.

A groomer may help with:

gentle brushing
bathing when appropriate
removing excessive loose coat
dealing with mats
reducing friction from an unmanageable coat
noticing changes in coat texture
helping you choose appropriate grooming tools

But groomers do not diagnose alopecia, thyroid disease, allergies, parasites, or skin infection.

Hair loss is one of those situations where grooming and veterinary care often need to work together.

Simple Action Plan

If you notice dog hair loss or thinning:

First, determine whether there is a real bald or thinning area rather than ordinary shedding.

Next, inspect the skin without scratching or irritating it.

Look for itching, redness, odor, flakes, scabs, wounds, parasites, or repeated licking.

Check whether collars or harnesses are rubbing.

Photograph the area.

Keep grooming gentle.

Do not start several shampoos, supplements, or home remedies at once.

Then contact your veterinarian if the thinning persists, worsens, or comes with other symptoms.

Final Thoughts

Dog hair loss and thinning deserve attention because the coat is often showing you what is happening with the skin — and sometimes with the rest of the body.

Normal shedding is expected.

Visible bald spots, progressive thinning, severe itching, redness, odor, scabs, or skin changes are different.

Instead of trying to make the hair grow back immediately, focus on identifying why it is disappearing.

Once the underlying cause is understood and treated, the coat has the best chance to recover.

Related Dematly Resources

Dematly provides general educational dog-grooming information and does not replace advice from a veterinarian or qualified professional groomer.