As a child, did you ever skin your knee and fear telling your parents, afraid of your
mom breaking out the brown bottle of pain containing hydrogen peroxide to “help heal”
your wound?
Given the agony it caused, you might have wondered whether the fizzing liquid was actually
helping, and why hydrogen peroxide bubbles when it comes in contact with your skin.
If you’re still wondering today, well, wonder no more.
To begin with, hydrogen peroxide does indeed kill bacteria, viruses, fungi and a whole
host of pathogens thanks to the fact that it is a powerful oxidizing agent.
So in theory it seems like a great idea to pour it on a fresh cut to help prevent infection.
It turns out, however, that while this has been a staple home treatment for cleaning
various cuts and abrasions for nearly a century, you probably shouldn’t use hydrogen peroxide
to disinfect your wounds.
To better understand why not, we’ll need to look at what hydrogen peroxide is and how
it manages to kill microorganisms.
hydrogen-peroxideChemically speaking, hydrogen peroxide, which is a naturally occurring molecule
within the human body, is two parts hydrogen and two parts oxygen (H2O2), with the molecule
held together by the two oxygen atoms.
As a result of these oxygen atoms having a very weak bond, the molecule breaks down rather
easily, potentially introducing free radicals into your system.
Left unchecked, this would all result in a host of problems within the human body.
In fact, because hydrogen peroxide’s claim to fame is primarily its great oxidizing effect,
up until relatively recently it was thought that its presence in the body had only damaging
effects.
However, recent research, such as that performed by the German Cancer Research Center (Deutsches
Krebsforschungszentrum) in 2014 was able to show that hydrogen peroxide is an essential
chemical messenger helping the body’s cells respond to outside hormones and growth factors.
As Dr. Tobias Dick sums up, “We know today that the body’s own H2O2 is vital for signal
processing in a healthy organism.”
That said, the level of H2O2 must be maintained in a specific range (between 0.05 micromol/l
and 117 micromol/l in exhaled breath, and in human fluid).
Too much and the damaging effects of oxidation will cause countless problems that can result
in cell death, among other issues.
Enter the enzyme catalase, which is found in almost all living things.
Catalase circulates throughout the cell, waiting to come into contact with the H2O2 being produced
by cellular respiration.
Once in contact, it rapidly converts it into water and oxygen (via two H2O2 molecules becoming
two H2O (water) molecules and one O2 (dioxygen) molecule).
In fact, the catalase is so good at its job, that it has one of the highest chemical conversion
rates of any enzyme.
A single catalase molecule can convert millions of hydrogen peroxide molecules every second.
(It is this water and oxygen being rapidly produced that results in the fizzing/bubbling
effect you see when the hydrogen peroxide comes in contact with the catalase.)
However, even with this efficiency, residual hydrogen peroxide will remain, allowing your
body to maintain the low concentration of hydrogen peroxide required for normal protein
signaling, while keeping it from reaching toxic levels that can destroy a cell.
Like all living things, bacteria, viruses, and many other pathogens have a myriad of
chemical reactions taking place within their cells.
Just as the oxidizing effects of hydrogen peroxide can ultimately potentially interrupt
these processes, it can also do the same to bacterial cells.
Thus, if this oxidizing agent is in high enough concentration, the result is a halt to normal
cellular processes resulting in the death of the pathogen.
So why the controversy today on whether you should use hydrogen peroxide on wounds?
As just mentioned, this oxidizing agent will also kill healthy human cells in sufficient
concentration.
Beyond this, it’s also thought that it may slow down the mechanisms of healing because
it interferes with the normal scaffolding processes involved with repairing skin damage.
(This interruption can also potentially lead to increased scarring, see: How Scars Form.)
This is all not to mention that if the oxygen gas produced by the large amount of hydrogen
peroxide coming in contact with the catalase enters your blood stream, it can circulate
throughout your body leading to countless medical problems like heart attack, stroke,
or pulmonary embolus.
While you might think this couldn’t possibly happen, hydrogen peroxide used as a topical
disinfectant has been implicated in several fatal and near fatal incidents due to this
oxygen gas being introduced into the bloodstream.
However, as yet it’s not entirely clear how the oxygen is getting there.
It may be that excess oxygen enters the capillary beds themselves, or that H2O2 (hydrogen peroxide)
molecules get absorbed into the bloodstream and then, in such relatively high concentration,
create the oxygen embolus.
Whatever the mechanism, the potentially life threatening complication remains.
So in the end, thanks to the propensity of hydrogen peroxide to cause damage to healthy
tissue, combined with the very slight risk of oxygen emboli after pouring it on a cut,
the use of hydrogen peroxide to clean wounds is usually not recommended anymore, presumably
much to the relief of six year olds the world over.
As for what you should do when cleaning wounds, most doctors will point out simply using normal
saline, a little elbow grease, and some over the counter topical antibacterial products
will have a much greater chance of preventing infection then the hydrogen peroxide would
anyway.