Alopecia management from a comparative perspective: pharmacological and pharmaceutical insights in humans, dogs, and cats.

Hair loss (alopecia) is a multifactorial condition affecting humans and companion animals, including dogs and cats, with etiologies involving hormonal, immune-mediated, genetic, infectious, allergic, parasitic, and behavioral mechanisms. Although androgenetic alopecia and alopecia areata are well characterized in humans, alopecia in veterinary patients more frequently reflects an underlying endocrine, hereditary, infectious, allergic, parasitic, or self-induced disorder. This review provides a comparative analysis of the pathophysiology, clinical presentation, pharmacological management, and pharmaceutical formulation of nonscarring alopecia across species. In humans, United States Food and Drug Administration-approved treatments, including topical minoxidil, oral finasteride, and selected Janus kinase inhibitors, are supplemented by emerging approaches such as platelet-rich plasma, low-level laser therapy, regenerative medicine, and nanotechnology-based delivery systems. In contrast, veterinary management primarily depends on identification and correction of the underlying disorder, with limited species-specific evidence and few dedicated formulations. Differences in follicular architecture, hair-cycle kinetics, skin permeability, drug metabolism, coat characteristics, and grooming behavior preclude direct extrapolation of human therapies to dogs and cats. Dermatophytosis further illustrates the One Health relevance of comparative alopecia management because successful control may require coordinated treatment of affected animals and humans together with environmental decontamination. This review highlights the need for species-specific clinical trials, safety assessment, and formulation strategies to support the development of effective and practical treatments for human and veterinary alopecia.