Matt: Maybe you can help me regain my $5. Say you’re on the coast of Baja, there’s no fresh water or medical services around, and you’re stung by a stingray. I’ve been told the best thing to do in this situation is to urinate on the wound, although the Poison Control Center strongly disagrees. This information came from a college professor of biology. — Mike English, San Marcos

It’s a well-known folk remedy, though I couldn’t find any folk who’d actually tried it or even knew anyone who had. Believers state that stingray venom is acid, urine is alkaline, so peeing into the wound neutralizes the poison. In fact the venom is only mildly acidic (pH 6.6; 7 is neutral). Some say you’re safer from infection if you flush the wound with your own urine than with potentially contaminated seawater. Most physicians would still recommend the seawater. I hope that fiver wasn’t on the professor.

The tail barb on a ray is viciously serrated and covered with a fleshy sheath. When an unalert beachgoer steps on a dozing ray, it whips its tail up and jams the barb into the bather’s foot or ankle or gashes his flesh. The sheath tears off the barb, and the venom is released. For the next 30 to 90 minutes, our hapless surf bunny writhes in excruciating pain. Assuming the victim will let anyone near his swollen, throbbing leg, the recommended first aid is to flush the area (yes, even with seawater) to remove as much venom as possible, then remove as much of the fleshy sheath as can be seen in the wound. (The biggest danger from stingray stings is infection, usually a result of bits of the sheath remaining in the wound.) Then stick the wound in water as hot as the victim can tolerate or apply hot compresses. That eases some of the pain and may help neutralize the venom, which is chemically unstable and loses its toxicity when heated. Stingrays use their barbs defensively against fish, so there’s not enough venom delivered in each sting to seriously affect the average healthy adult human (though beware of an allergic reaction to the venom’s protein and of stings to the upper body, near the heart, which are more dangerous than wounds to extremities). Most people stung by rays ride out the pain without consulting a physician and without lasting injury. But a quick check by a doctor is the safest course, especially if you haven’t had a tetanus shot in more than ten years. And increase your chances of avoiding the whole painful thing during San Diego’s ray days (July and August) by scuffing your feet through the sand when walking in shallow water. Then you’ll only have to worry about the broken glass and medical waste.