My son wonders why we sweat more under our arms than other places. And why it smells more. Any takers? — Stephanie S.

We sweat about the same everywhere, but under our arms and in our groins there is not much air circulation, so the sweat doesn’t evaporate, so we notice it. More moisture and also somewhat higher temperatures than the rest of our skin provide good growing conditions for bacteria. The hair in our armpits and groins provides lot of surface area for the bacteria to grow on. Bacteria feed on stuff that we sweat out, and on dead skin cells. Their waste products are smelly. Apparently the Romans used to shave their armpits to reduce the smell by reducing the culture surface. Various peoples use a variety of salts, which are toxic to bacteria, to reduce the population. Every time you put on deodorant, you kill off millions of bacteria.