# Why does tap water sting a wound? **URL:** \ **Category:** Factual Questions\ **Created:** [April 29, 2004, 12:37pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658 "2004-04-29T12:37:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [April 29, 2004, 12:37pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/1 "2004-04-29T12:37:57Z")
I haven`t tried distilled water. However, tap water when used to rinse a wound will burn or sting. Saliva doesn`t sting. What in the water causes the stinging? (I`m guessing it has something to do with the treatment process and pure water should not sting.) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 29, 2004, 12:52pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/2 "2004-04-29T12:52:20Z")
My guess would be that it is something to do with osmosis; your body fluids are concentrated solutions, tapwater is a very dilute solution; meaning that water is going to be taken up by your exposed tissues, possibly quite rapidly and this might cause stimulation of nerve ends. Come to think of it, the nervous system itself operates on a delicate balance of salts and ions; introducing weak solutions to it (or near to it) might directly stimulate nerves. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [April 29, 2004, 2:17pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/3 "2004-04-29T14:17:25Z")
Umm…because it _doesn’t_ ? I’ve never experienced this at all. :dubious: ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [April 29, 2004, 2:46pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/4 "2004-04-29T14:46:03Z")
> [@Bosda Di'Chi of Tricor](#): > > Umm…because it _doesn’t_ ? > > I’ve never experienced this at all. :dubious: Does too. Try it some time. I`ve got a cut on my finger and when I get my hands wet (before lathering up with soap) I get the burning sting. I had a head wound that I noticed this with too. When wetting my hair before using shampoo I`d get the sting. It`s only temporary, maybe 15 or 20 seconds. ---
**Author:** ![fortytwo](https://avatars.discourse-cdn.com/v4/letter/f/f9ae1b/32.png) [@fortytwo](https://boards.straightdope.com/u/fortytwo)\ **Post date:** [April 29, 2004, 2:53pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/5 "2004-04-29T14:53:15Z")
Could it be Chlorine? We’ve had to fit a filter in our shower-head because of skin irritation. It ruined my home beermaking activities as well. ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [April 29, 2004, 3:00pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/6 "2004-04-29T15:00:28Z")
Mangetout is correct. Your cells have a semipermeable membrane surrounding them. Inside cells, electrolytes are at a certain concentration. When exposed to fluid that is hypotonic (lower amounts of these electrolytes) there is movement of h2o across the membrane, and cells swell/burst. When they talk about “Normal Saline” it is a 0.9% solution of NaCl which is isotonic. Distilled water would be even more hypotonic than tap water. ---
**Author:** ![mmmiiikkkeee](https://avatars.discourse-cdn.com/v4/letter/m/edb3f5/32.png) [@mmmiiikkkeee](https://boards.straightdope.com/u/mmmiiikkkeee)\ **Post date:** [April 29, 2004, 3:53pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/7 "2004-04-29T15:53:57Z")
I’ve found that open cuts and so forth sting when you have a combination of: 1. cold water (colder than the skin temp anyways) 2. dirty salty sweat mixing in. The second one would describe both of your scenarios; wetting hands/hair before washing them (I’m guessing they were dirty right?) for a few seconds dissolves and spreads around whatever is on the skin around the cut into it. When you lick a cut your tongue is the same temp, doesn’t dribble all over the place and splash stuff around, plus you’ve got another sense (taste) to distract you and you might not notice the stinging as much. ---
**Author:** ![MaryEFoo](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MaryEFoo](https://boards.straightdope.com/u/MaryEFoo)\ **Post date:** [April 29, 2004, 4:46pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/8 "2004-04-29T16:46:50Z")
And following **vetbridge** and **mangetout** , your saliva has the same concentration as the fluids in your cells. IIR, Jacques Cousteau said that a cut in seawater did not have that sting. He attributed it to the saline concentration being the same. ---
**Author:** ![Velma](https://avatars.discourse-cdn.com/v4/letter/v/85e7bf/32.png) [@Velma](https://boards.straightdope.com/u/Velma)\ **Post date:** [April 29, 2004, 5:23pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/9 "2004-04-29T17:23:58Z")
Really? I’ve scraped myself in the ocean before and it hurt like heck. Going in with razor burn or cuts hurts too, more than tap water. Freshwater lakes don’t make my cuts sting. I’ve had cuts sting sonetimes in tap water and I always thought it was the chlorine, but now come to think of it it’s not any worse in a pool or hot tub, both of which have much more chlorine in them. ---
**Author:** ![Trigonal\_Planar](https://avatars.discourse-cdn.com/v4/letter/t/0ea827/32.png) [@Trigonal\_Planar](https://boards.straightdope.com/u/Trigonal_Planar)\ **Post date:** [April 29, 2004, 10:12pm UTC](https://boards.straightdope.com/t/why-does-tap-water-sting-a-wound/242658/10 "2004-04-29T22:12:54Z")
I once swam in a heated, salted pool. I could open my eyes underwater with no problem, unlike freshwater or chlorinated pools, which cause much stinging. Its a very weird senstation; such pools are very soothing.