The human body runs two separate sweat systems, and only one of them was built for cooling. The other — the apocrine system — sits in a narrow set of places: the underarms, the areolae, and the sub-pelvic and perineal region. It stays dormant through childhood, switches on at puberty, and produces…

Every woman carries two entirely separate sweat systems beneath her skin, and they behave nothing alike. One is a plain cooling mechanism that keeps the body from overheating. The other is a slower, richer, more curious system that clusters in only a handful of places — the underarms, the area…

Every woman carries a small, self-regulating laboratory that she never has to think about. It measures its own acidity, adjusts its own chemistry, and maintains a setting so specific that scientists can express it as a single number.