What causes a horse to lose hair on her face and rear?

Ringworm:

- fungal infection that causes circular areas of hair loss

- highly contagious

Insect bites (e.g., mites, lice, or fleas):

- intense scratching can lead to hair loss.

- inspect coat for evidence of insects or nits

Cushing's Syndrome/Pituitary Pars Intermediate Dysfunction (PPID)

- disorder of pituitary gland (small gland at base of brain)

- excessive hair loss from face, body, and tail as well as sweating & increased drinking & urination

Other possible causes. include

- sun exposure

- nutritional deficiencies

- allergies

- skin cancer

- bacterial infections.

- equine protozoal myeloencephalitis (EPM), a neurologic condition caused by a protozoan parasite of the central nervous system

- hypothyroidism