"My dog is losing fur in patches"

Why dogs lose fur in patches — and why the pattern matters

Unlike general shedding, which spreads evenly across the whole coat, patchy fur loss means something is interfering with the hair follicle in a localized way. The follicle either stops producing hair, gets damaged by inflammation or infection, or gets physically disrupted by the dog's own scratching and chewing. The shape, location, and texture of the bald patches are your most important diagnostic clues — a roughly circular patch with a slightly scaly edge points toward ringworm, while symmetrical patches on both flanks with no itching typically signal a hormonal problem like hypothyroidism.

The most common causes fall into four categories: parasitic (mange, caused by Demodex or Sarcoptes mites), fungal (ringworm, despite the misleading name), hormonal (hypothyroidism, Cushing's disease, or sex hormone imbalances), and allergic or immune-mediated (atopic dermatitis, food allergies, or the body attacking its own follicles in a condition called alopecia areata). These require different treatments — which is why reaching for a generic "fur loss shampoo" without knowing the cause usually produces disappointing results.

Age, breed, and lifestyle all affect which cause is most likely. Demodex mange, for example, is common in young dogs and immunocompromised adults, while hypothyroidism tends to appear in middle-aged to older dogs of medium and large breeds. A puppy with circular bald patches picked up from a shelter environment is a very different situation from a seven-year-old Labrador with symmetrical flank alopecia and weight gain.

Patchy fur loss isn't one problem — it's several, with different causes

The location, shape, and accompanying symptoms of the bare patches tell very different stories. Pick the description that most closely matches what you're seeing.

What happens if you wait — and when waiting is actually fine

Some causes of patchy fur loss are genuinely self-limiting. Localized Demodex mange in young, otherwise healthy dogs, for instance, often resolves on its own as the immune system matures. But the conditions that look similar — Sarcoptes mange, ringworm, and hormonal disorders — do not get better on their own, and some actively worsen. Sarcoptic mange spreads rapidly across the whole body and can transfer to other pets and people in the household. Untreated hypothyroidism leads to worsening skin and coat quality, weight gain, and cardiovascular effects. The cost of treatment also tends to rise the longer these conditions are left unaddressed, both in terms of vet bills and the dog's discomfort.