A hippo's 'blood sweat' is actually a built-in sunscreen and antibiotic
Hippos secrete a thick, reddish fluid from special glands that long ago earned the nickname 'blood sweat,' even though it's neither blood nor ordinary sweat. Chemists isolated two pigments in it — one red, one orange — that absorb ultraviolet light and inhibit bacterial growth, protecting the hippo's skin as it basks in equatorial sun for hours. It's a rare documented case of an animal producing its own topical sunscreen.