pink sweat

I found out recently that hippopotamuses (or hippopotami, as those who took middle school Latin like to kick it) have pink sweat. An excerpt from ScientificAmerican.com explains:

Q: Do hippopotamuses actually have pink sweat?

A: Hippos secrete a reddish oily fluid sometimes called "blood sweat" from special glands in their skin. But the fluid is not sweat. Unlike sweat, which some mammals (including humans) secrete onto their skin, where it evaporates and therefore cools the body, this fluid functions as a skin moisturizer, water repellent and antibiotic. It appears red when exposed to full sunlight, which led the first European discoverers in Africa to call it "blood sweat."

Hippos mostly try to avoid direct sunlight by lying in water during the day and feeding at night. Their skin is very sensitive to both drying and sunburn, so the secretion acts like an automatic skin ointment. It also protects the skin from becoming waterlogged when a hippo is in the water. The detailed chemical composition of this secretion, which is unique to hippos, remains something of a mystery.

How, you might ask, did I come by this information? Not from reading an educational article in National Geographic, I assure you. No, not flipping through Discovery Channel or Animal Planet either. As it so happens, I woke up the other morning, having been plagued by nightmares the night before, drenched in sweat, and when I took my shirt off to hop into the shower, I noticed the armpits of my sleep shirt looked obscenely pink. Hence, a quick search on "pink sweat" turned up interesting hippo trivia.

No need to worry - I'm ok, but thank you for your concern. It seems to have been a unique chemical reaction between my t-shirt, then-sweat and my latest laundry detergent.