I have noticed that stressful situations cause my armpits to become smellier, but not necessarily sweatier. What effect does adrenaline and cortisol and similar hormones have on under-arm flora?
Hi Maryl, thank you for your question. It is often said that stress-sweat smells more unpleasant than 'normal' sweat. Here is the theory behind it: stress leads to the production of adrenaline. Adrenaline has a vast effect on the apocrine sweat glands (also a bit on the eccrine -and apoeccrine- sweat glands, producing mainly water and salts, but more on the apocrine glands, which produce lipids, fatty acids, fatty acids bound to amino acids, etc.). The apocrine glands contain lots of bacteria, which already transform the long-chain compounds into volatile compounds. It is the 'mother nest' of body odor. Under stress, the content of the apocrine sweat glands is secreted onto the skin, causing an immediate malodor. Not for everyone, only for those who have the malodorous bacteria present inside the apocrine glands. This effect goes back to the animal kingdom. An animal which is hunted upon has the selective advantage if its fur or skin is more slippery and lipid-rich, and can thus run faster away through the woods. The animal has an additional selective advantage if a sudden malodor is released, making him less attractive for its predator.
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