Hair shed by dogs and cats is frustrating to any owner tired of reaching for the vacuum cleaner and the lint brush. But sudden, excessive or otherwise abnormal hair loss, including the appearance of any bald patches, calls for a veterinary evaluation.

Often, fur is lost as pets scratch or chew at an itch due to fleas or allergies. This usually leaves red, inflamed skin and broken hair stubble.

Other times, hair loss may be related to endocrine problems such as low levels of thyroid hormone, diabetes or an abundance of natural cortisol in the body, a condition called Cushing’s disease. Hormonal problems often have other signs such as sluggishness, increased hunger and thirst, or darkened skin. Blood tests are typically needed for diagnosis.

So if you notice a bald patch on your pet or more fur on the sofa, it may be time to check in with a veterinarian.