Hair loss can be caused by a lack of hair growth due to underlying disease, but hairs may also be broken off due to overgrooming or an imbalance of the skin barrier ecosystem.
Common conditions causing hair loss in cats include:
- flea-bite hypersensitivity and other parasites,
- fungi (ringworm) or baterial overgrowth,
- allergies (atopy, food, contact)
- stress or pain-induced overgrooming.
Less common causes include sebaceaous adenitis, pseudopelade, autoimmune disorders, Cushing’s disease, feline hyperaesthesia and cancer.
Bald patches or areas with decreased hair density appear. The underlying skin of the area concerned can seem normal or it can show redness, bumps, scabs and crusts. Sometimes, the condition is itchy and the cat will constantly lick or scratch the area which is the cause of alopecia.
As the cat's hair density is important (more than a dog) and as their hair diameter is rather uniform, it can be difficult to assess a partial hair loss. It's then easier to see patchy alopecia than diffuse alopecia.
Note that a decreased hair density in the area between the eye and ear can be completely normal. Consult your vet, who will focus on identifying the underlying problem and will advise you on managing the condition.