Quick answer: Hair loss in cats is most often caused by over-grooming from stress or allergies, but can also indicate fleas, ringworm, or hormonal imbalance.
Cats that lick excessively create symmetrical bald patches on the belly, inner thighs, and flanks. This is frequently stress-related — household changes, new pets, or disrupted routine can trigger it. The skin underneath is usually normal with no redness or scaling.
Fleas cause intense itching even in cats that show no obvious flea signs — check for flea dirt (black specks that turn red on wet paper towel) at the base of the tail and belly. Ringworm, a fungal infection, creates circular patches of hair loss with slightly scaly skin around the edges.
See a vet if the skin under the bald area is red, broken, or crusty; if hair loss is spreading; if your cat seems uncomfortable; or if other symptoms appear alongside it. Most causes of hair loss are treatable once the specific cause is identified.
Hair loss is a symptom, not a diagnosis. Over-grooming from stress is most common in indoor cats, but a vet visit is the reliable way to rule out medical causes and start appropriate treatment.