hair,as in hot weather or if not washed for several days. Earwax is partly composed of sebum.
All of the sebaceous glands in humans have been demonstrated to show similarity in structure and secrete sebum by a holocrine process. Sebum excreted by the sebaceous gland is primarily composed of tryglicerides, wax esters, and squalene. Wax esters, like squalene, are unique to sebum and not developed anywhere else in the body. Sebum also contains 45% water-insoluble fatty acids known to have broad antimicrobial activity. Additionally, sebaceous gland secretion provides Vitamin E to the upper layers of facial skin. Sebaceous lipids contribute to maintain integrity of skin barrier, and express pro-inflammatory and anti-inflammatory properties. Recent research suggests that sebum may represent a delivery system for antioxidants, antimicrobial lipids, pheromones, and hydration of stratum corneum. During the last gestation trimester, it is known that sebaceous glands produce vernix caseosa w/c protects the embryonic skin from amniotic water. Sebaceous secretions in conjunction w/ apocrine glands also play an important thermoregulatory role. In hot conditions, the secretions emulsify and foment formation of and prevent the loss of sweat drops from the skin. In colder conditions, sebum repels rain from skin and hair Increased facial surface sebum secretion is also associated w/ the development of acne.