Approach to Alopecia in Dogs in Clinical Practice

Alopecia in companion animals, particularly dogs, represents a complex clinical manifestation with diverse etiologies ranging from infectious agents and endocrine disorders to congenital and hereditary abnormalities. The skin, as the body's largest organ, plays a critical role in maintaining homeostasis, acting as a barrier against environmental insults while contributing to thermoregulation, vitamin D synthesis, and sensory perception. Hair follicles, derived from ectodermal-mesenchymal interactions, are vulnerable to a wide range of pathological insults. Alopecia may be focal or multifocal, and its presentation—symmetrical or asymmetrical—can provide clues to the underlying pathology. Common causes include bacterial folliculitis, dermatophytosis, demodicosis, and various autoimmune or hormonal imbalances. Congenital and hereditary forms, such as ectodermal dysplasia and color dilution alopecia, are breed-specific and often diagnosed via skin biopsy and histopathology. Among acquired causes, endocrine disorders like hypothyroidism, hyperadrenocorticism, and hyperestrogenism disrupt normal follicular cycling and keratinization, resulting in progressive hair loss. Follicular dysplasias and alopecia X, although primarily cosmetic in nature, remain diagnostic and therapeutic challenges due to their unclear pathogenesis. Management strategies are etiology-specific and include antiparasitic, antimicrobial, hormonal, and palliative treatments such as melatonin or essential fatty acids. A detailed clinical history, dermatological examination, and targeted diagnostics are essential to guide treatment and provide prognosis.