From http://www.medicinenet.com/script/main/art.asp?articlekey=35284&page=2 Humans possess three major types of skin glands--sebaceous glands, eccrine (or sweat) glands, and apocrine glands. Sebaceous glands are most common on the face and forehead but occur around all of the body's openings, including eyelids, ears, nostrils, lips, and nipples. This placement is particularly handy, as the secretions of these glands kill potentially dangerous microorganisms. They also contain fats that keep skin supple and waterproof and, on the downside, cause acne. Little is known, however, about how sebaceous glands contribute to human body odor. The sweat glands exude water and salt and are non-odorous in healthy people. That leaves the third potential source of a human pheromone--the apocrine gland. Apocrine glands hold special promise as the source of smells that might affect interpersonal interactions. They do not serve any temperature-managing functions in people, as they do in other an...