Scratch 'n' sniff technology combined with fabric means mere movement triggers a burst of scented freshness.

A sweaty gym sock you can use as a room freshener?

This is Sandra Tsing Loh with the Loh Down on Science

and with happy news from chemist Alirio Rodrigues of Portugal's University of Porto. He's taken the fragrance-filled microcapsules found in scratch-and-sniff stickers, and embedded them in fabric.

When people wearing the fabric MOVE--say, sprint a hundred-meter dash, or do anything that raises their body temperature--the capsules burst open, and release their fragrant contents.

Folks wearing the socks suddenly smell like they're walking through a field of flowers! Or, more likely lemons, since that's the smell Rodrigues chose.

Why hasn't someone done this before?

It's because most scratch-n-sniff items use capsules made from formaldehyde. That's the stinky preservative you may remember from high school biology. Unfortunately, formaldehyde can potentially cause cancer. Not a good fashion choice for humans.

But Rodrigues discovered that an environmentally friendly plastic called polyurethane-urea works just as well. Posing no health hazards, it even holds up after repeated dry-cleaning.

Now if they could just freshen up my kids' underpants. They can? Fantastic! I choose kiwi! With a strong piney underscent. Thanks!