Most cases have a predisposing cause such as ectoparasitism, endocrinopathy, underlying allergy, etc. The inflammation targets the follicles.
Inflammatory cells are in the wall and canal of hair follicle.
Furunculosis occurs when the follicular wall is destroyed by the infiltrate, releasing contents into the dermis. Follicular contents such as hair, keratin, mites, or bacteria incite further inflammation. Papules, pustules, crusts, erythema, patchy and motheaten alopecia. A close inspection may reveal a pustule or papule with a central protruding hair indicating active inflammation of the follicle. Feline acne - PMNs Pelodera infestations Arthropod bites Microscopic example of three different views of skin of a young Great Dane with Demodicosis.