Dr. Christie Wilcox for Quartz:
I’ve watched tentacles from box jellies and Portuguese man o’ war react to urine. And more often than not, the solution causes their venomous stinging cells to fire. Though the intensity of the reaction varies along with the urine itself, at best, urine is inert, at which point you might as well use seawater instead. And at worst, pee causes so much stinging that the jelly would almost certainly inject more venom into you.
Douse the sting with vinegar!
So here’s what you should do: keep your pants zipped and stash a bottle of vinegar in the car instead. Treating the wound with vinegar causes the jellyfish’s stinging cells to become fixed and unable to fire.
Venomous snakes are some of the most dangerous venomous animals, capable of delivering large amounts of potentially lethal toxins with a single bite. Because snake venom can be so dangerous, I can see why people began to think that removing the venom before it spread through the body could save victims’ lives. But why we then settled on the idea that the best way to solve the problem is to suck on the wound to draw the venom into our own mouth is beyond me.
Unfortunately, a lot of proposed ways of removing venom, from suction devices to cutting around a bite (“lancing”), don’t work. Once snake venom is injected in the body, it immediately goes to work, hitchhiking in the blood to get around. It only takes 60 seconds for your blood to travel all the way around your body—so you’re never going to get to all of the venom before it’s spread.
i.e just go get help!