Don't sweat it!

No antiperspirant could mask a hippopotamus's sweat. Turns out, that's a good thing: Japanese scientists discovered that the hippo's stinky, sticky, blood-red sweat contains red and orange pigments (colored chemicals) that kill deadly germs and block harmful sunrays.

Like people, hippos sweat to cool off. A clear mixture of salt, water, and other chemicals oozes from hundreds of glands (organs that produce and secrete chemicals) under a hippo's skin. As the fluid evaporates (changes from a liquid to a gas) off the skin, it whisks away heat.

But before the sweat vanishes into thin air, pigments turn the clear liquid a bright red. "The little droplets of liquid look like pink polka dots all over their skin," says Tony Barthel, assistant curator at the National Zoo in Washington, D.C. This rosy glow helps the hairless hippos avoid a sunburn. That's because the sweat's pigments absorb the sun's damaging ultraviolet rays (invisible energy waves).

The pigments also act as antibiotics (substances that kill microorganisius). That's a lifesaving feature for male hippos, which often get injured when sparring with their sharp teeth over territory. "The antibiotics protect the wounds from infection [by disease-causing microorganisms]," says Kimiko Hashimoto, one of the researchers at Kyoto Pharmaceutical University in Japan. Who knew sweat could be so sweet?