The most significant structural properties of the skin of the brows and glabella are (a) one half or more of the follicles produce vellus hairs; (b) all follicles are so richly vascularized and innervated that they are comparable to the vibrissae follicles of nonhuman primates; (c) many acetylcholinesterase-positive nerves penetrate the epidermis, pilary canal, and perhaps the outer root sheath of follicles; (d) the follicles in the brows, but not in the glabella are free of arrectores pilorum muscles; (e) eccrine sweat glands are few or absent; (f) the dermis, like that of the skin anywhere on the head normally contains great quantities of elastic tissue, even in the young.
Montagna W. Histology and Cytochemistry of Human SkinXXXIV. The Eyebrows. Arch Dermatol. 1970;101(3):257-263. doi:10.1001/archderm.1970.04000030001001