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Is urine really sterile? Can you use it to disinfect things? – SF, The Woodlands, TX

Thanks, SF! Let’s talk about pee!

The answer to your first question is a very clear “no.” Urine is not sterile. Sure, it’s sterile as when it’s first made in your kidneys, but then it passes through your urethra, and like pretty much every part of you that comes in contact with the outside world, your urethra contains bacteria, and some of them end up in your urine. In some cases (like urinary tract or bladder infections) the bacterial levels can be quite high, but in general they are low – not sterile, but probably safe enough to drink, at least from a bacterial contamination standpoint. However…

It’s never a good idea to drink your own urine. Some survivalists say they have done it, including that guy who had to cut off his own arm in Utah after getting pinned under a boulder, but it’s probably not something he made a habit of – and for good reason. While urine is 95% water, the other 5% is stuff that is not good for you. This 5% contains urea, excess electrolytes and other stuff your body is trying to get rid of. To put this in context, salt water from the ocean contains about 96.5% water with 3.5% salt. If you drink salt water, the salt just dehydrates you, defeating the purpose of drinking water in the first place. Over time, if you drink enough of it, seawater can kill you. Urine will do the same thing, only it is also full of urea and other body waste products and is totally gross. Don’t drink urine, ever.

As to the second part of your question, even if it were sterile, urine would not sterilize things you poured it on. Pouring sterile things on other things does not sterilize them. Think of it this way – if you had pure sterile water and poured it on your skin (which is loaded with bacteria), your skin would not be sterile – it would just be wet. In order to sterilize something, you need a disinfectant – something that will actively kill the bacteria or viruses on the skin surface. Anti-bacterial soap might work, but if you really want it sterile, you would need to use something more powerful, like rubbing alcohol, bleach, or an iodine-based disinfectant (betadine). Madonna once claimed that she cured her athlete’s foot with urine. This will absolutely not work and (say it with me!) you should never take health advice from celebrities.

Also, urine does not effectively treat jellyfish stings. We assume that this myth was born when a couple of devious kids convinced a friend who had recently been stung to let them pee on him just to see if he would let them do it. They probably never thought it would work, but their foolish friend was in so much pain that he called their bluff. In order to cover their tracks after what was probably an uncomfortable couple of minutes for all involved (and not get in trouble with their parents?), they made up the silly urine/jellyfish myth, and it spread like wildfire because it’s kinda funny. In reality, urine will make most stings worse. Try vinegar instead.