Eponychium

In human anatomy, the eponychium [Greek epi (on, upon) + onychion (little claw)], is the thickened layer of skin surrounding fingernails and toenails. It can also be called the medial or proximal nail fold. Its function is to protect the area between the nail and epidermis from exposure to bacteria. The vascularization pattern is similar to that of perionychium.

In hoofed animals, the eponychium is the deciduous hoof capsule in fetuses and newborn foals, and is a part of the permanent hoof in older animals.