Common Causes of Hair Loss in Dogs: When Should You Worry?
More fur on the sofa is often just normal shedding. A new bald patch, thinning coat or sore-looking skin, however, deserves a closer look.
Hair loss in dogs—known as alopecia—can result from parasites, allergies, infections or conditions affecting hair growth. Finding the cause is the first step towards suitable treatment.
Is it normal shedding or hair loss?
Normal shedding usually leaves the coat covering the skin. New bald patches or areas becoming noticeably thinner deserve attention.
Gently part the fur and check for redness, scabs, flakes or sores. Compare the area with your dog’s usual coat: some dogs naturally have less hair on their belly or ears.
The appearance of a patch alone cannot tell you what caused it. Your vet will consider the skin, coat and your dog’s overall health.
Common causes of hair loss in dogs
Fleas and mites
Parasites can irritate the skin, leading to scratching, biting and coat damage.
Demodex mites can cause patchy hair loss, particularly in puppies or dogs with other illnesses. There may be little or no itching unless a secondary infection develops.
Skin allergies
Allergies can cause repeated scratching, chewing or licking, leaving thin or bald areas. Red skin and recurring ear or skin infections may also occur.
Environmental allergens or food allergies can be involved, but hair loss alone does not identify the trigger.
Skin infections
Bacterial infections and ringworm—a fungal infection, despite its name—can cause patchy hair loss.
Ringworm patches may look circular, but their shape alone is not enough for a diagnosis. Your vet may need skin or hair samples to identify an infection.
Hormonal conditions
An underactive thyroid or Cushing’s disease can affect the coat. Hormonal hair loss often develops in a similar pattern on both sides of the body and may not initially be itchy.
Symmetrical thinning is a useful clue, but it does not confirm a hormonal problem.
Inherited or hair-growth conditions
Some dogs develop coat thinning associated with inherited conditions or changes in the hair-growth cycle.
Seasonal flank alopecia, for example, can cause patches of hair loss on the sides of the body. Other causes may need to be ruled out before a diagnosis is made.
Other possible causes
Skin damage, nutritional deficiencies and certain medicines can also affect hair growth.
Repeated licking may remove hair, but discomfort or itching should be investigated before assuming stress or boredom is responsible.
What should you do?
Take clear, well-lit photographs and record:
When you first noticed the change.
Whether the affected area is spreading.
Any scratching, licking or chewing.
Changes in appetite, thirst, energy or weight.
Recent changes to food, medicines or grooming products.
These details can help your vet decide which checks are needed.
Avoid starting creams, oils or supplements specifically to treat hair loss before the cause is assessed. Different conditions need different care.
When should you contact a vet?
Book an appointment for new bald patches or unexplained thinning, even if your dog seems comfortable.
Contact your vet promptly if the skin is painful, bleeding, oozing or rapidly worsening, or your dog seems unwell.
Mention changes in behaviour, appetite or energy—even when the skin itself looks relatively normal.
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This article provides general information and does not replace professional veterinary advice.
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