Wikipedia:Reference desk/Archives/Science/2019 August 9

= August 9 =

Pain from disinfectant caused by iodine or isopropanol or both?
In a solution of 3% iodine in 70% isopropanol, would you expect the iodine or the isopropanol to be mostly responsible for the pain/stinging when used to disinfect damaged skin? — Preceding unsigned comment added by 79.70.240.20 (talk • contribs)
 * It's primarily the alcohol. This thread isn't the best source, but it does explain it well.  The isopropanol causes cellular damage by dehydrating your cells; when pain receptors in the skin are damaged in this way, they send a pain signal to the brain.  Your unbroken skin is protected by a layer of hardened cells (the Stratum corneum, lit. "horny layer") that protects the cells underneath from this effect, but when your skin is broken, the isopropanol is able to get at your less protected cells.  Iodine also causes cell damage, but through a different mechanism; it acts as an oxidizing agent akin to chlorine bleach or hydrogen peroxide.  Tincture of iodine, as this preparation is known, is used because there are two different mechanisms (dehydration and oxidation) that can be used to kill pathogens; however whatever kills a pathogenic cell can also kill your cells, and the pain you feel is a physiological response to this cell damage.  -- Jayron 32 15:56, 9 August 2019 (UTC)
 * I'm wondering which alcohol(s) beat isopropanol for cell dehydration power and what disqualified them for most common first aid. If methanol is one obviously the 1 sip kill or blind thing. I've seen ethanol OTC but denatured to avoid having to be sold in a liquor store. Sagittarian Milky Way (talk) 18:11, 9 August 2019 (UTC)


 * I'm no sure that you need anything stronger. If it kills 100% of the cells it touches, that's good enough. And you do want to limit collateral damage to the skin. Bleach, for example, will kill microbes, but is also nasty on the skin. When I got some on my skin, I had to apply moisturizer for days, before it stopped feeling dry and itchy. SinisterLefty (talk) 18:17, 9 August 2019 (UTC)
 * And because damaging your tissues is actually a bad thing, the standard advice for care of typical wounds (example) is to simply wash with soap and water, and cover with a dressing. Application of plain petroleum jelly to the wound before dressing is also recommended by some sources; the jelly serves as a physical barrier against infection and traps moisture, which improves wound healing. Disinfectants are unnecessary and can damage your own tissue, which impedes healing. Applying antibiotics (as in antibiotic ointments, with Neosporin being one popular brand) is even worse because that promotes antibiotic resistance. (Again, this is for typical wounds. If a wound is severe enough to require medical attention, seek it and follow the directions of medical professionals.) --47.146.63.87 (talk) 22:33, 9 August 2019 (UTC)


 * I use different methods for treating wounds, depending on the case. If I stepped on a filthy, rusty nail, you better believe I am pouring antiseptic all over the wound (I use hydrogen peroxide, 3%). But if I cut myself on a knife after I washed it, then no disinfectant is required. SinisterLefty (talk) 22:55, 9 August 2019 (UTC)
 * A better idea is to ensure your tetanus immunization is kept up-to-date. A deep puncture wound should probably be looked at by a medical professional in any case. Tetanus prophylaxis may be indicated. Deep tissue or organ (such as nerve or bone) injury is possible and may require treatment. --47.146.63.87 (talk) 23:54, 9 August 2019 (UTC)
 * @SinisterLefty H2O2 is no longer recommended for disinfecting wounds. See Hydrogen_peroxide. Matt Deres (talk) 19:43, 11 August 2019 (UTC)


 * Pedantry: although the alcohol probably has an antiseptic effect, its primary purpose in tincture of iodine is to solubilize the iodine, as iodine is poorly soluble in water. Also, tincture of iodine sensu stricto is rarely used today; the most widely used iodine antiseptic is povidone-iodine solution. This is generally superior because it is less irritating and the antiseptic effect persists longer. I note that even the photo in tincture of iodine actually depicts povidone-iodine solution, as stated in the caption. Maybe this is misleading in the article? --47.146.63.87 (talk) 23:54, 9 August 2019 (UTC)