Why is my dog losing so much fur?

Heavy shedding in dogs falls into physiological and pathological causes. Physiological causes are usually seasonal shedding, in which dogs lose large amounts of fur each spring and autumn. This is normal, and the amount drops once the molting season ends.

Pathological causes of shedding are varied and may include skin diseases from bacterial, fungal, or mite infections. These typically cause severe localized hair loss, itching, skin redness, and heavy dandruff.

Abnormal thyroid hormone secretion can also cause shedding, usually in a symmetrical pattern, and requires prompt veterinary treatment.