Symptom guide

Why Is My Dog Losing Hair? Bald Patches and What Causes Them

Normal shedding or a problem? Common causes of hair loss and bald spots in dogs, from fleas and allergies to mange, ringworm and hormone disorders.

Updated October 2026 · 7 min read · By the Hushku editorial team · 3 sources

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Short answer

Even shedding all over is normal, especially in spring and autumn. Bald patches, thinning coat, or hair loss with itching, redness, scabs or a smell are not. The most common causes are fleas, allergies, skin infections, mange mites and ringworm; hair loss on both sides of the body without itching can point to a hormone problem such as an underactive thyroid or Cushing's disease. A vet visit with simple skin tests usually finds the cause.

Key facts

Even seasonal shedding is normal; bald or thin patches are not.
Itchy hair loss usually means fleas, allergies, infection or mites.
Symmetrical, non-itchy hair loss can be hormonal (thyroid or Cushing's).
Sarcoptic mange and ringworm can spread to people.

This guide is general information, not a diagnosis. If your pet seems unwell, or you're worried, call your vet.

Overview

All dogs shed, and double-coated breeds like Huskies, German Shepherds and Labradors "blow" their undercoat seasonally, losing huge amounts of fluff for a few weeks. That's normal, and the coat underneath stays full.

What's not normal is hair loss that leaves bald or thin patches, or that comes with itching, red or scaly skin, scabs, a greasy feel or a bad smell. Hair loss in dogs (alopecia) is a sign, not a diagnosis, so the pattern matters.

Is it itchy? Itchy hair loss is usually caused by parasites, allergies or infection, and dogs often lick or chew the hair off themselves. Non-itchy hair loss, especially if it's symmetrical on both flanks, is more likely to be hormonal.

Go to a vet now if you see

Raw, oozing or rapidly spreading sores (hot spots), especially with pain
Hair loss with lethargy, fever or not eating
Swollen, painful skin or a wound that smells

Common causes

1. Fleas and flea allergy
Usually mild
Hair loss and scabs over the lower back and tail base. One bite can trigger itching for days in an allergic dog.
2. Environmental and food allergies
Needs a vet
Itching and chewing at the paws, face, ears, armpits and belly, often with recurring ear and skin infections.
3. Bacterial or yeast skin infections
Needs a vet
Red bumps, rings of scale, greasy skin and a musty smell. Usually secondary to allergies.
4. Mange (Demodex or Sarcoptes mites)
Needs a vet
Demodectic mange causes patchy hair loss, often around the eyes and face in young dogs, and isn't contagious. Sarcoptic mange is intensely itchy, starts on ear tips and elbows, and spreads to other dogs and people.
5. Ringworm
Needs a vet
A fungal infection that causes round, scaly patches of hair loss. It can spread to people and other pets.
6. Hypothyroidism
Needs a vet
An underactive thyroid in middle-aged dogs causes a thin coat, weight gain, lethargy and a 'rat tail'.
7. Cushing's disease
Needs a vet
Thin skin and hair loss on the body, with drinking and peeing more, a big appetite and a pot belly.
8. Pressure points and licking
Usually mild
Calluses on elbows in large dogs, and lick granulomas on the legs from boredom, anxiety or pain.

What you can do at home

Check for fleas with a flea comb over white paper; black specks that turn red when damp are flea dirt.
Treat every pet in the home with a vet-recommended flea product, every month.
Stop your dog licking or chewing a sore area with a cone or soft recovery suit until it's checked.
Don't shave double-coated dogs to reduce shedding; the coat may grow back patchy.
If ringworm is possible, wash hands after handling your dog and wash its bedding hot.

When to see a vet

Bald patches, thinning or broken hair
Hair loss with itching, redness, scabs, dandruff or smell
Symmetrical hair loss, or hair loss with weight gain or drinking more
Itchy spots appearing on people in the household

Prevention

Year-round flea control for every pet in the home
Regular brushing to spot problems early and remove dead undercoat
Manage allergies with your vet before skin infections take hold
Feed a complete and balanced diet

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Sources

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

What tests will the vet do?

Usually a flea check, skin scrapes for mites, tape or impression tests for yeast and bacteria, and a fungal culture or PCR for ringworm. Blood tests check thyroid and adrenal hormones if they're suspected.

Can stress make dogs lose hair?

Stress causes more shedding in the short term, such as at the vet. Anxiety can also lead to over-licking that leaves bald spots, often on the legs.

Is mange contagious to people?

Sarcoptic mange (scabies) can cause itchy spots in people. Demodectic mange isn't contagious to people or other dogs.

Key facts

Overview

Go to a vet now if you see

Common causes

1. Fleas and flea allergy

2. Environmental and food allergies

3. Bacterial or yeast skin infections

4. Mange (Demodex or Sarcoptes mites)

5. Ringworm

6. Hypothyroidism

7. Cushing's disease

8. Pressure points and licking