Interfollicular

Interfollicular is an anatomical term used to designate tissue or spaces that lie between hair follicles. It is commonly applied in dermatology, histology, and pathology to differentiate regions or patterns that are not associated with follicular structures from those that surround or involve follicles directly.

In the skin, hair follicles are arranged in networks that form follicular units, typically including the hair follicle, sebaceous gland, and arrector pili muscle. The interfollicular region refers to the portions of the epidermis and dermis that are not part of these units. The interfollicular epidermis covers much of the non-hairy surface of the body, while in hairy skin the interfollicular area sits between adjacent follicles. The interfollicular dermis lies between follicular units and contains connective tissue, blood vessels, nerves, and other resident cells.

Clinically and pathologically, interfollicular distribution is a key descriptor. Pathologists may distinguish interfollicular inflammation or infiltration from folliculotropic involvement, where disease processes predominantly affect the hair follicles themselves. This distinction can aid in diagnosis and influence treatment decisions across various dermatologic conditions, including certain inflammatory diseases and cutaneous lymphomas.

Etymology: inter- meaning between and folliculus meaning a small bag or sac, reflecting the concept of spaces between follicles. The term emphasizes spatial arrangement rather than specific tissue type and is used across descriptive dermatology and histopathology.