Hippo sweat is natural sunscreen

Hippo "sweat" contains substances that fight microbes and screen out ultraviolet light.



Sweat can stain your shirt and leave a lingering odor. If you were a hippo, things could be even worse: Your sweat would have a red-orange color.

Now, say scientists from Japan, hippo sweat has a good side, too. It blocks the sun’s harmful rays and fights disease-causing microbes.


When a hippo sweats, its skin releases colored substances that may prevent infection and sunburn.



Hippo sweat isn’t really sweat because the glands that produce it are bigger and deeper than those that produce sweat in people and other animals. The liquid comes out of skin holes that are easy to see. This liquid may help a hot hippo cool down, but it’s just as easy for a hippo to lumber into water to cool off.

For the new study, keepers at the Ueno Zoo in Tokyo used gauze pads to collect secretions from hippos. Scientists then analyzed the liquid and identified two chemicals that color a hippo’s sweat. Both are highly acidic compounds.

In the lab, the researchers found that the sweat’s red pigment keeps two types of disease-causing bacteria from growing. This may help explain why hippo gashes and wounds rarely seem to get infected, even though male hippos have frequent, fierce fights.

Tests also showed that both pigments absorb ultraviolet light. The sun’s ultraviolet rays can cause sunburn and even skin cancer. The hippo’s sweat acts like a sunscreen, protecting the animal’s skin from damage.

Chemists may someday use their new knowledge to make medicines or sunscreens. You won’t be seeing bottles of hippo sweat at the cosmetics counter anytime soon, though. A sunscreen that turns you red-orange and doesn’t last very long probably wouldn’t be a best-seller.

More Stories from Science News Explores on Animals