ABSTRACT
Unique biochemical and immunological events dictate the complex cyclic growth and differentiation patterns of hair follicles and their associated sebaceous glands (1), structures that are collectively referred to as pilosebaceous units. Once regarded as mere evolutionary remnants, hair follicles and sebaceous glands have been recognized increasingly as significant pathways for percutaneous transport (2). Percutaneous transport routes via the lipoidal domains of the stratum corneum have been well established (3,4), whereas comparatively less is known about the specific roles of hair follicles and sebaceous glands. Determination of the roles of these structures is complicated by the lack of adequate animal models and methodologies that can distinctly distinguish follicular and stratum corneumpathways.Moreover, it may be possible that a topically applied compound traverses more than one pathway simultaneously.
