Heat right way to ease ray's sting

Our family is spending the school holidays at Matapouri Bay, where we've seen a lot of stingrays. No one has been stung yet, but if it does happen what is the best way to treat a sting? - GH
Stingray envenomations can be excruciatingly painful. You step on a ray in the shallows, and its tail flicks up and pokes you in the foot or ankle.
Within minutes come waves of intense pain that peak within the first two hours, but can keep coming in waves for a day or more.
The stingray's spine is a modified cartilage scale, with razor-sharp serrated barbs and poison-filled grooves, sheathed in a fleshy coating full of toxins. These toxins cause pain, promote bleeding, and kill cells. Only rarely do the toxins cause vomiting, cramps, palpitations or seizures.
If you get stung you need hot water, and plenty of it. Fill a sink with the hottest water you can tolerate without scalding, and soak the injured extremity for half an hour.
The heat is thought to deactivate the liquid toxins, which are very heat-sensitive, cooking them into a gel. In one study, half an hour of hot water immersion at 45C was 90 per cent effective in stopping pain. That's remarkably effective for any treatment in medicine.
Even if you are pain-free you should probably be seen in the emergency department or by your GP. They will look for broken-off spines embedded under your skin, sometimes using x-ray or ultrasound if they think one is in there.
The wound will be irrigated to flush out the fleshy toxic bits, and local anesthetic used if the pain isn't relieved by heat or if barbs need to be removed.
In some cases, antibiotics will be prescribed in the hope of preventing infection, which is fairly common with stingray injuries.
Most cases will heal nicely on their own, but in the past year I've seen a couple of unlucky individuals end up with festering wounds for months after the injury, in part because the circulation to the legs is poor to begin with.
Prevention is more effective than cure. Watch where you're stepping, and try to walk with a shuffling gait so the rays can move away. And if you do get poked, fire up the kettle or run a hot bath because, with stingray injuries, the right first-aid can make a big difference.
Gary Payinda MD is an emergency medicine consultant in Whangarei.
Have a science, health topic or question you'd like addressed? Email: drpayinda@gmail.com
(This column provides general information and is not a substitute for the medical advice of your personal doctor.)