Science Chicago – LIFE’S A LAB!

It is 92 degrees today in Chicago (hot hot hot), and on the Metra train this morning I had a really smelly experience.  My train partner, who decided to sit next to me, was sweating profusely in his suit and must have forgotten to shower and put on deodorant (it was the 7:01am train).  His body odor was a stench.   It had the strength of the Hulk, the power of a Jedi, and the permeability of Aquaman.  It was pungent and unstoppable.  Squashed next to the window (no other seat was available), I breathed through my mouth so to avoid the smell for the hour commute.

Humans are smelly.  The strongest human odor comes from the armpits, and most people find it really smelly (like I did) and use deodorant which covers up the smell.  Scientists have traced the odor to the apocrine glands attached to hair follicles in the armpit. These glands are larger and more numerous in the armpit than elsewhere in the body.  Males have more apocrine glands than females, and therefore men can smell worse than women.

Apocrine glands produce only small amounts of secretions each day.  These secretions are odorless, but the odor comes from the deterioration of the secretions by the billions of bacteria that live on everyone’s skin.  There are dozens of different types of microbes on the skin and the microbial population is known as a flora.  The secretions from the apocrine glands in the armpit contain a complex mixture of compounds, and scientists are still trying to figure them out.

There is no such thing as a bad smell, but there are smells, and it just depends on how you perceive them.  For example, whatever smell I find repulsive, my Aunt’s dog Crystal may find irresistibly appealing; but back to humans.   Humans have noses for a reason:   body odor is specific to the individual (that’s right it’s genetic), and we use it (along with our other five senses) to identify people.  Our noses are involved in gathering useful information from the environment in the form of chemosignals, more commonly known as pheromones.  Other people’s apocrine glands, in other words their armpits, are putting out a lot of important social information.  These armpit odor molecules are sucked up into our sinuses, processed by our brains, and translated into attraction or repulsion.  Men’s body odors, given they have more apocrine glands, are stronger than women’s, and this peculiar smell can communicate a lot of information about their individual genetic quality.  Women, in contrast, have an amazing olfactory sense, which sniffs out the mate value of prospective reproductive partners.

My train partner’s body odor was repulsive to me this morning, but maybe on his ride home he might attract someone else’s nose.

-Heather

“I will do science to it.”
- Dresden Codak