Ever noticed how your friends' homes have a distinct scent—but yours doesn't? Or wondered why the smell of your perfume doesn't get to you after a while? It's essentially because your brain has noticed these scents, registered them as unproblematic, and decided to ignore them, an expert explains to the Science of Us.

You initially notice smells in your environment as molecules reach your nostrils, but after your brain puts them in the non-dangerous category, "the receptors in your nose sort of switch off," says cognitive psychologist Pamela Dalton.

The purpose of this process, scientists think, is to allow us to pick up on new smells as soon as they emerge. "Whatever is new in your environment, that huge signal rises above the rest,” Dalton notes. Want to find out what your home smells like to others? More blood flow may help; try some exercise. It also might help to take a break; after vacations, Dalton points out, we often recognize our houses' smells, thinking it seems a little musty inside. So if you're looking for a fresh take on your favorite perfume, maybe don't use it for a while, Yahoo suggests. (As for your own scent, it can attract or repel mosquitoes.)

More From Newser