Dog & cat health · Vet-reviewed guide

Why Is My Cat Losing Hair? Causes and Fixes

Cats lose hair for reasons that range from harmless to worth-a-visit — allergies, stress-grooming, parasites, or something under the skin. The pattern often tells the story.

Quick answer: If you are asking why is my cat losing hair, the most common answer is over-grooming driven by an itch — most often a flea allergy — rather than the hair simply falling out on its own. Cats are meticulous groomers, and when something makes them itchy they lick and pull so much that the hair thins or bald patches appear, often on the belly, legs, or back.

The itch behind it is usually an allergy (to flea bites, food, or environmental triggers like pollen and dust mites), but hair loss can also come from parasites like mites, ringworm (a fungal infection), hormonal problems such as an overactive thyroid, and, less commonly, stress. Because the fix depends entirely on the cause, and the causes look similar from the outside, hair loss is a reason to see a vet rather than to treat the skin directly. This guide covers the real causes and when your cat needs care.

About hydroxyzine for dogs & cats: this is a prescription medication your veterinarian can prescribe. Read our guide, or ask us if you need help sourcing it.

The most common cause: over-grooming from an itch

A cat losing hair is usually pulling it out by over-grooming an itchy area, not shedding it passively.² The single most common trigger is flea-allergic dermatitis, where a cat reacts strongly to flea bites, so reliable flea control is an important first step even if you cannot see fleas.

The main causes to consider

• Allergies. Flea, food, and environmental allergies are the leading reasons for itch-driven hair loss.¹
• Parasites. Mites (mange) and fleas.
• Ringworm. A fungal infection that causes patchy hair loss, often circular, and can spread to people and other pets.
• Hormonal disease. An overactive thyroid or other imbalance, more common in older cats.
• Stress (psychogenic alopecia). Some cats over-groom from anxiety, but this is diagnosed only after medical causes are ruled out.²

Why it needs a vet, not a home fix

These causes look alike from the outside, and the tests that separate them, skin samples, a ringworm check, a flea trial, and bloodwork for thyroid disease, are veterinary steps.¹ Treating the skin with creams or supplements without knowing the cause usually fails, and an antibiotic does not fix hair loss unless there is a specific bacterial skin infection. Hair loss is a symptom, not the disease itself, so treating the skin without finding the cause is not the answer. Ringworm in particular needs proper diagnosis because it spreads.

When to see a vet

See a vet if your cat is losing hair in patches, has red, scabby, or sore skin, is grooming obsessively, or has other signs like weight loss or increased appetite (which can point to thyroid disease).² A vet finds the cause and treats it. Any prescribed medicine must come from a vet. See how our vet prescription service works. If the itch centers on the ears, see our ear mites guide.