And how does it clean open wounds? Hope effective is it compared to rubbing alcohol and why would I use one over the other?
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Hydrogen peroxide bubbles because it’s mostly water with a very reactive chemical inside (the H202)
When H2O2 encounters most things it’s happy to lose that ‘extra’ oxygen, creating compounds that are often gasses (making those bubbles) and water in the process.
It kills bacteria and can destroy viruses by breaking the chemicals that make them up, as the oxygen bonds with them to make new compounds. Oxidation/bleaching like this is bad for living things (you are protected by being covered by layers of un-alive skin).
Hydrogen peroxide solution is about as effective a topical antiseptic as alcohol solutions, and used much the same way. Hydrogen peroxide can be better for some sensitive tissues.
Hydrogen peroxide works via a chemical process called a redox reaction. Essentially the peroxide is bonding with the cell walls it comes in contact with. This strips Oxygen atoms from the cells and turns into water and O2. That O2 is the gas you see bubbling from a wound treated with peroxide. Unfortunately peroxide is indiscriminate. It is killing the bacteria yes but it is also killing the exposed tissue cells and immune cells of your body. While not the same reaction, rubbing alcohol can have much the same effect; killing immune cells and healthy cells. Either way both will lead to longer healing times for the wounds, and the longer a would stays open, the more likely it is to get infected.
It is always best to use antibiotic ointment over either peroxide or rubbing alcohol, but if you don’t have that on hand…still don’t do that. Warm water and hand soap should be all you need. If even that isn’t available then fine use them, but neither peroxide or rubbing alcohol should be your first choice. Nor should it be your second choice.
Hydrogen peroxide is not a very stable molecule. It consists of two hydrogen atoms and two oxygen atoms – very close to water, H2O, but with an extra oxygen. The structure is H-O-O-H, with the two oxygen atoms bound together and the hydrogen atoms at the end.
Oxygen atoms are very “clingy” when it comes to electrons. They really want more electrons and they are willing to share, but only with other atoms that aren’t as grabby. Oxygens really don’t like to share with each other, because they’re both trying to be super grabby. So, any time you have an O-O bond, it’s not going to be a very stable molecule. However, oxygen atoms **really** do not want to be alone with only their own electrons and will grab onto almost literally any other atom in order to get their electrons.
When hydrogen peroxide is mixed with clean water, there’s nothing else for the oxygen atoms to grab onto, so they just stay grabbed onto each other. If you give them something else to grab onto – say, the proteins on the outside of bacteria cell walls – the O-O bonds quickly fall apart and the hydrogen peroxide *decomposes*. One of the oxygen atoms will grab onto the other hydrogen atom and create a nice, stable molecule of H2O.
The other oxygen atom is now completely alone and that is *super* unstable, so that oxygen atom is going to grab onto whatever is nearby that isn’t H2O – like that bacteria protein. Alternatively, both oxygen atoms will grab *hard* onto proteins and whatnot, leaving the hydrogen atoms to stick to each other, creating H2 gas molecules. That’s what creates the bubbles – it’s hydrogen gas being liberated from the H2O2 as the oxygen grabs onto everything else.
Oxygen grabbing onto things is generally bad for those things. That’s what rusting is – oxygen grabbing onto iron atoms. If the oxygen atom is grabbing the electrons from the other atom, then those electrons are no longer available to be shared with whatever molecule that atom was in, usually causing that other molecule to fall apart. So the oxygen literally rips other molecules apart. That’s how hydrogen peroxide cleans your wounds – it destroys the pathogens. It’s also destroying your own, healthy cells, but you have a lot of those, while the pathogens have only themselves.
You may wonder why the O2 molecules in the air don’t do this. Well, they *do*. Oxygen is really bad for you, except that it’s so good at grabbing electrons that we can use it to liberate a lot of energy. Our bodies have a lot of tools to control oxygen so that it doesn’t break things that it shouldn’t, and we have other tools to fix the things that inevitably break anyway. Hydrogen peroxide is just way more aggressive, because the hydrogen atoms make it less stable. Hydrogen is also pretty aggressive, so although most of it will end up as H2, some of it will attack whatever else is nearby, too.
Studies have shown that hydrogen peroxide is generally not great for disinfecting if you already have access to clean water and soap. The damage to your own cells slows down healing and recovery, so you’re better off cleaning the wound with warm, soapy water, and then applying an antibiotic ointment, covering the wound with a clean bandage, and keeping it clean.
To add to my edge case, I scuba dive often. In high school, I was a competitive swimmer and often suffered ear infections. As a 40+year old adult and diver, literally after every dive, if I don’t treat my ears with either rubbing alcohol or hydrogen peroxide, I get ear aches. If I forget and start to feel the onset of an ear infection, using either quickly resolves the issue, why?
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