In a recent op-ed feature in the Chicago Tribune by Mark Jacob and Stephan Benzkofer, entitled "10 Things You Might Not Know About Sweat," the authors note that hippopotamus sweat may be the next big thing in skin care. They further that it not only regulates heat, but also repells insects, protects the animal from UV radiation and keeps microbes away.
A further search on hippo sweat, led Cosmetics & Toiletries to an article in Nature authored by researchers at Keio University who found antibiotic and sunscreen activity in the red liquid.
A posting by Ask Nature, a project of the Biomimicry 3.8 Institute, explains that it is the pigments in this red sweat, namely red hipposudoric acid and orange norhipposudoric acid, that absorb light from 200-600 nm. The hipposudoric acid also inhibits the growth of bacteria at low levels.
If suppliers and manufacturers are not already working on synthesizing hipposudoric acid for skin and sun care, perhaps this "river horse" research could inspire future research.