Apocrine glands form in utero, but don't go into action until puberty when they receive cues from all the hormonal stimulation taking place. Although the apocrine glands continually release sweat, they kick into high gear every time emotional stress occurs. In fact, the more you experience emotional stress, the more your apocrine glands contract and release sweat [source: Britannica]. The amount you sweat is, aside from emotional triggers, probably hereditary. Still, it can be influenced by other factors, such as your consumption of caffeine, alcohol or spicy foods. Some over-the-counter drugs, including aspirin, can cause excessive sweating [source: Weil].
What does this have to do with hair follicles? They play a central role, acting as straws through which sweat is transported from an under-the-skin factory to the surface. Here's a play-by-play: From deep within the skin, apocrine glands release sweat from a coiled tube into a straight tube-like duct that ascends toward the hair follicle. This duct contracts until it has squeezed the sweat into the hair follicle. Once there, the sweat empties into the isthmus, which is the part of a hair follicle directly underlying the skin [source: Baker]. The sweat is then released from the hair follicle onto the skin's surface. Knowing the relationship of apocrine sweat glands to hair follicles makes it easy to understand where this type of gland congregates: wherever hair follicles grow.
There are specialized versions of the apocrine gland, too. Although not quite the same, these first-cousin glands produce earwax and, in the case of the female gender, breast milk. We should also point out apocrine sweat is quite different from the mostly water sweat secreted from other glands; it's fatty and has the potential to be quite odiferous. We'll explain why on the next page.