Hydrogen Peroxide Experiments




Does 3% hydrogen peroxide kill germs?


Answer: My experiments show that hydrogen peroxide either kills germs outright or somehow prevents them from growing on an agar plate. It probably doesn't kill all types of bacteria, and I can't test for viruses. 






Experiment Details


In this experiment, I compared the bacteria killing power of regular 3% hydrogen peroxide (in the brown bottle from the pharmacy section at Walmart), Essential Oxygen Food Grade 3% hydrogen peroxide, and pure white vinegar. This is the basic procedure that I always use to test cleaning products on the countertop. First, I used masking tape to section off squares on my kitchen countertop and labeled them according to what I would be testing. I made sure that my countertop was very clean to start with, of course.






Next I made germy water. To do this I mixed a small scoop of mud from our back yard into purified water. Then I poured the muddy water through a paper towel to filter out the chunks. I was left with very dirty water which contains lots of bacteria. For some experiments, I also scraped bacteria off of an already grown agar plate from a previous experiment and mixed those germs in. This way my "germ water" had lots of bacteria in it.








I put 1mL of germ water onto each square with the exception of the "clean" control square using these 1mL syringes.







I rubbed the germ water around the square with my gloved finger. Then I let the squares dry completely which took 2-3 hours.





Once the squares were dry, I put .5mL of each cleaning product onto its respective square. For this experiment, I used 5 mL of 3% hydrogen peroxide, 5mL of Essential Oxygen 3% hydrogen peroxide, .5mL white vinegar, and .5mL water on the respective squares.





I rubbed the cleaning product around to completely cover the square using a clean gloved finger. I went over the square a few times to make sure that the cleaning product completely covered it. Then I set a timer and let the cleaning product sit on its square for 5 minutes.





After the allotted time, I used a sterile swab to swab the square. Most squares were still wet after 5 minutes. I rubbed all over the square but I did not touch the tape (just in case the tape held onto bacteria and interfered with the experiment).



Then I scribbled all over an agar plate with the swab.



If you want to do these experiments yourself, I used these agar plates available on amazon. They come with the sterile swabs.





The plates were incubated for 24-48 hours in my homemade incubator consisting of a plastic box and a heat lamp. The temperature was about 90 degrees F. Any bacteria present on the plate will grow and multiply. After about 24 hours you can see colonies (or piles) of bacteria on the plates. It is important to remember that viruses do not grow on these plates. Just bacteria and some fungus. Also not all types of bacteria grow on these plates. So, a clean looking plate does not necessarily mean that there were no microorganisms whatsoever were present. It just means that nothing that could grow on the agar plate was present. However, this is still a very valuable information for comparing different cleaning products.







Understanding Agar Plates

In case you are new at looking at agar plates, let me explain. Agar is a Jello-like substance that bacteria and fungus like to grow on. The whitish/yellowish dots you see are colonies (or piles) of millions of bacteria. Some types of bacteria are not able to grow on these agar plates. Viruses can not grow on these agar plates. So, just because a plate looks clean, doesn't mean that no microorganisms whatsoever were present. We assume that a clean plate means that most bacteria were killed. However, there is the tiny possibility that the cleaning product just stopped the bacteria from growing as opposed to actually killing it. Also, I can't make any determination as to the time it took the product to kill the bacteria since the product was still with the bacteria on the agar plate. (Both the bacteria and the cleaner would be picked up in the sterile swab.) So, I don't know if it took 1 minute to kill the bacteria or hours. These experiments are still very useful when used to compare cleaning products and cleaning methods. 

Results










As you can see, both the regular 3% hydrogen peroxide and the Essential Oxygen 3% hydrogen peroxide seem to do a fabulous job killing bacteria. Pure white vinegar was not as effective. I use 3% hydrogen peroxide as a control in most of my experiments. 

Disclaimer: I can't be 100% sure that the hydrogen peroxide or any product that I test is actually killing the bacteria as opposed to preventing it from growing on the agar plate by some other means. 

I cannot guarantee that 3% hydrogen peroxide will kill ALL bad bacteria and viruses. There are probably plenty of germs that the 3% hydrogen peroxide won't kill.  Here is a research paper stating that 3% hydrogen peroxide is good for killing salmonella and e.coli. However, other research shows that it is NOT good for killing norovirus. (That is why I recommend keeping chlorine bleach or the Clorox Hydrogen Peroxide products on hand for emergencies when someone is throwing up. Those products have been tested and proven to kill norovirus surrogates.) 



I also found these travel sized bottles of 3% hydrogen peroxide. I bought one, tested it, and it worked great. You can refill them. 

Does 3% hydrogen peroxide kill germs in the kitchen sink?

Answer: It either kills them or just stops them from growing.  



Experiment Details

I tested pure white vinegar and hydrogen peroxide on my kitchen sink and my neighbor's sinks. We have a 2 sided stainless steel sink. First, I rinse the sink really well to make sure it looks clean. Then I swabbed the sink and rubbed the swab on an agar plate to see how much bacteria was in the sink. Then I sprayed 30 sprays of 3% hydrogen peroxide all over one side and let it sit for 5 minutes. I did not wipe at all. Then I swabbed that side. Then I sprayed 30 sprays of pure white vinegar all around on the other side and let that sit for 5 minutes. I swabbed that side and the plates were incubated for 48 hours in my warm incubator. 
 




As you can see, the 3% hydrogen peroxide did a great job killing germs in the sinks. The pure white vinegar killed some germs but not as many as 3% hydrogen peroxide. However, when I swab the sink, the hydrogen peroxide is still on the swab. (So, is the vinegar). This is because I did not rinse the sink before swabbing. So, I don't know WHEN exactly the hydrogen peroxide is killing the germs because it sits on the agar plate with the germs. Keep reading and I repeat this experiment with rinsing. 

Disclaimer: I can't be 100% sure that they hydrogen peroxide or any product is actually KILLING the germs in these experiments as opposed to somehow preventing them from growing on the agar plate by some other means. 


How fast does hydrogen peroxide kill germs?

Answer: It is not as fast as I hoped.  

In most of my countertop and sink experiments, I test cleaning products for 5 minutes and then swab the surface. However, usually the cleaning product is still on the surface and gets picked up with the bacteria on the swab. The product is incubating on the agar plate with the bacteria. So, I don't know if the product killed the germs in 1 minute or 24 hours. (Of course, the products that don't appear to kill germs, don't kill them even in 24 hours.)  Here is a research paper showing that 3% hydrogen peroxide killed salmonella and e.coli in 1 minute. So, I decided to do some tests with my 3% hydrogen peroxide to see how long it takes. 


Experiment Details

I decided to test how long it takes for 3% hydrogen peroxide to kill germs in the sink. First, I swabbed both sides of a dirty sink and rubbed the swabs onto agar plates. Then I sprayed both sides with a ton of 3% hydrogen peroxide (about 40 sprays per side to completely cover the sink). After 5 minutes, I swabbed the right side of the sink and rubbed the swab onto an agar plate. This plate would have 3% hydrogen peroxide on it. Then I used the kitchen sink tap water/hose to thoroughly rinse off the left side of the sink. This would rinse the hydrogen peroxide off. Then I swabbed the left side and rubbed that swab onto an agar plate. The plates were incubated for 48 hours. 

Results


As you can see, the 5-minute swab from the side of the sink that still had hydrogen peroxide on it was all clean as usual. The side of the sink that was rinsed to remove the hydrogen peroxide, still had a lot of bacteria. From this we can conclude that 5 minutes is NOT long enough for the hydrogen peroxide to kill all the germs in the sink. I also took a swab of that neighbor's tap water and rubbed it onto an agar plate to make sure the water didn't contain bacteria. It did not. 

I repeated the experiment in another sink and left the hydrogen peroxide for 10 minutes. I swabbed the right side of the sink with the hydrogen peroxide still on it. I rinsed the hydrogen peroxide off the left side and then swabbed it. 



As you can see, there was still bacteria left in the sink after 10 minutes. However, it certainly seems like the 3% hydrogen peroxide is killing a lot of it in 10 minutes. I repeated the experiment again. This time I used 10% chlorine bleach on one side of the sink and 3% hydrogen peroxide on the other side of the sink. I used about 40 sprays on each side of the sink to fully cover it. They both sat for 10 minutes. Then I swabbed them both with the cleaner still on. Then I thoroughly rinsed them both and swabbed again. 




As you can see, the swabs where the cleaner was still on the sink were very clean as usual. The swabs from the sink that was rinsed after 10 minutes still had some germs. The 10% chlorine bleach did better than the 3% hydrogen peroxide. One reason that they both might not have done a perfect job is because the cleaner didn't really STAY on the sides of the sink. It dripped off right away. It does seem like 3% hydrogen peroxide does a whole lot of germ-killing in that first 10 minutes. 

I repeated the experiment on my sink. First I rinsed all the debris out of the sink and rubbed off any food particles that was stuck on. I swabbed my dirty sink and rubbed that swab onto an agar plate. Then I thoroughly sprayed the sink with 3% hydrogen peroxide. I used at least 40 sprays on each side and tried to cover everything. Then I let it sit all night for 9 hours. The sink was perfectly dry in the morning. In the morning, I thoroughly rinsed the sink and swabbed it again. 


As you can see, spraying the sink with 3% hydrogen peroxide and leaving it all night did a great job. I repeated that experiment a week later without using hydrogen peroxide. As a control, I just rinsed the sink out and swabbed the sink at night. Then I let the sink dry all night. I rinsed it again in the morning and swabbed it.


As you can see, just letting the sink dry all night did NOT kill the germs. I have known this for a long time. I always test neighbors sinks and sometimes they have been out of town for a few days and their sinks are dry but they are still very germy. 

So, if you want to disinfect your kitchen sink with 3% hydrogen peroxide, this is what I would do. At night, wipe out the sink with a washcloth or scratch pad, and then retire that cloth to the laundry. Then rinse out the sink with water. Then thoroughly spray it with 3% hydrogen peroxide. It is important to wipe around the edge of the sink with a clean cloth or paper towel so the hydrogen peroxide doesn't bleach the countertop. Then leave the hydrogen peroxide sit on the sink all night. I wear gloves when I use 3% hydrogen peroxide because it is hard on my skin, and I can't guarantee it or anything else is perfectly safe for you. 

Disclaimer: I can't be 100% sure that they hydrogen peroxide or any product is actually KILLING the germs in these experiments as opposed to somehow preventing them from growing on the agar plate by some other means. However, in the sink experiment where I rinsed the hydrogen peroxide off, it is gone from the bacteria. So, it really seems like the hydrogen peroxide is killing the bacteria. 

Can I use 3% hydrogen peroxide to clean the toilet?

3% hydrogen peroxide is not sold to be a cleaning product. So, I can't say for sure that it is safe for you and for household surfaces. After I realized that 3% hydrogen peroxide took at least 10 minutes to kill the majority of the germs in the kitchen sink, I began to wonder about my toilet cleaning regiment. For years, I have sprayed off my toilets with 3% hydrogen peroxide, grabbed a handful of toilet paper, and wiped the toilet down. I did not wait 10 minutes. I usually didn't wait one minute. However, I've swabbed my toilets many times (hours after I cleaned them so there was no hydrogen peroxide remaining) and nothing ever grows. Here is a swab of my "dirty" toilet compared to a swab of my neighbor's dirty toilet.


So, my regiment of spraying off the toilet with hydrogen peroxide and quickly wiping it down seems to be doing a good job. I'm sure the wiping itself contributes to the effectiveness. However, I think the key here is that I spray off the toilets and wipe them down AT LEAST once a day. The downstairs guest toilet that gets used by lots of neighbor kids and little boys that can't aim is wiped down several times a day. Why do I want my toilets this clean? Well, nearly all contagious illnesses are spread through poop, including influenza and stomach bugs. We have a big dog and my floors are always filthy. But I want those potties clean. 

If you are cleaning a dirty toilet, or should I say a "normal person's toilet" with hydrogen peroxide, I would spray it until it is soaking and dripping with 3% hydrogen peroxide, let it sit for 10 minutes, then wipe it all down. Wipe down the floor around the toilet right away because 3% hydrogen peroxide can fade the floor. Then I'd repeat the spraying with 3% hydrogen peroxide, sitting for 10 minutes, and wiping down. After you get it to that clean point, you can move onto quick cleanings like I do every day. 

In this experiment, I swabbed a dirty toilet before and after wiping it with just paper towel and water. I used a ton of paper towel and made heroic efforts to get it clean with just paper towel and water.
 

As you can see, wiping with just paper towel and water removed a lot of the germs. 

Here is an experiment where I swabbed a dirty toilet before and after cleaning with 3% hydrogen peroxide. I only let the 3% hydrogen peroxide sit for 5 minutes, and then I wiped it all down the best I could. 


It did not get the toilet as clean as I wanted it. That is why I now recommend leaving the 3% hydrogen peroxide sit for 10 minutes. And if your toilet is filthy like this, repeat the whole process and clean it twice. I need to repeat this experiment for 10 minutes, but I'm waiting for a neighbor's toilet to get good and dirty again. I have done experiments showing that Lysol Disinfectant Spray also does a great job killing the germs on a filthy toilet if you spray it until it is soaked and dripping, leave it sit for 10 minutes, and wipe it down. You also have to where a ventilation helmet because the Lysol fumes are terrible. You can see those results on my Lysol page. 

Of course, if anyone in the house has any type of vomiting or diarrhea illness, you should spray down the toilet with a solution 10% chlorine bleach in water or the Clorox Hydrogen Peroxide Spraywhich has been tested and shown to kill stomach bugs. 3% hydrogen peroxide probably isn't strong enough to defeat norovirus. 

Can I disinfect the countertop with 3% hydrogen peroxide? 

As I have said before, 3% hydrogen peroxide is not sold to be a cleaning product. I just like to use it, anyway. I it can fade the countertop and wood floor if you leave it on too long.  I wear gloves when I use it. Here is a countertop that I sprayed with 3% hydrogen peroxide. I let it sit for only 2 minutes and wiped it down with paper towel. I swabbed the countertop before and after. It got every clean. 



I cleaned that same countertop a 9 days later with just paper towel and water. That got pretty clean, too. 




Do I have to use so much hydrogen peroxide?

Answer: The surface needs to be fully covered with any disinfectant to actually kill the germs. 




How long is a bottle of 3% hydrogen peroxide good?


Answer: At least a month if you keep the cap on tightly and keep it in its original brown bottle. 





Experiment Details

Hydrogen peroxide is relatively unstable. So, it is not a good idea to use really old bottles of hydrogen peroxide. However, the 3% hydrogen peroxide sold at the store (which I use) is STABILIZED. They have added something to it to make it more stable. I've ask the hydrogen peroxide companies what this "stabilizer" is but they won't give me any information. I hope and assume that the stabilizer isn't too bad since the product is approved for use directly on wounds and as a mouth rinse. 

I decided to test a bottle of hydrogen peroxide that was opened for a month. I had taken some out and used it a few times during the month, but I kept the lid on tightly the rest of the time. I did the same countertop experiment that I always do. I made germ water with dirt from the back yard and bacteria scraped from a previous days "dirty hands" plate. I put 1mL of germ water onto each square on my countertop. I rubbed the germ water all around the squares and let them dry. Then I added .5 mL of each product onto the appropriate square. I spread them around to completely cover the square and set a timer for 5 minutes. After 5 minutes, I swabbed each square and rubbed the swabs onto an agar plate. The plates were incubated for 24 hours in my warm incubator. 





As you can see, the 1 month old bottles of hydrogen peroxide all did great! In this experiment, I had added a few drops of Thieves and Lavender oils to bottles of hydrogen peroxide. The addition of the Thieves and Lavender did not appear to hurt the ability of the hydrogen peroxide to kill germs. 




I also tested a bottle of Essential Oxygen is a food grade 3% hydrogen peroxide that had been opened AT LEAST 6 months. I had kept the cap on tightly but I had used it a few times. I tested it in a countertop experiment.






It still did really well killing bacteria after 6 months.



Is 3% hydrogen peroxide dangerous to people?



 Hydrogen peroxide is not a foreign chemical to your body. Your body actually produces hydrogen peroxide to help kill germs. However, the hydrogen peroxide your body produces is stored securely in vesicles. It is not just floating around. So, will a little hydrogen peroxide penetrating your skin while you clean hurt you? I don't know for sure. The 3% hydrogen peroxide bottle says that it is for wound cleaning and mouthwash. I am hoping that since it is okay to put on wounds and in your mouth, that cleaning with it wouldn't harm you. 

3% hydrogen peroxide is not sold to be a cleaning product. I would not recommend assuming that it is harmless. Yes, hydrogen peroxide eventually turns to oxygen and water, but before that it produces the hydroxyl free radical which is what does the damage to the germs. The hydroxyl free radical can also damage you. I would not put it on cuts or in your mouth unless your doctor or dentist tells you to. Do not drink it. Do not spray it in your nose. Try not to breath the vapors. I wear gloves when I'm cleaning with it, because it is very drying to the skin. 

A website viewer wrote to me and is certain that at age 24, she completely and permanently lost her sense of smell after using hydrogen peroxide to clean for 1 month. However, she went overboard and coated all the surfaces in her house and furniture with it. I still have a good sense of smell, and I've been cleaning with 3% hydrogen peroxide for 3 years. I spray off my toilets every day with 3% hydrogen peroxide. I clean the bathroom countertops with hydrogen peroxide 2-3 times a week. I spray out the bathtub with hydrogen peroxide once a week. I spray out the kitchen sink with hydrogen peroxide 2-3 times a week. I am not a medical doctor, though. Feel free to ask your doctor if it is safe to clean with hydrogen peroxide. 

Hydrogen peroxide also has stabilizers that may or may not be harmful. Also, there is more expensive "food grade" hydrogen peroxide available. This hydrogen peroxide still has stabilizers but they are approved for use on food and food contact surfaces. So, this one would be a better choice to spray off a baby's high chair tray. The link I have here is for  Essential Oxygen 3% Hydrogen Peroxide. The stabilizer in it is sodium acid pyrophosphate which is low risk according to the Skin Deep Website. The food grade comes as high as 35%. Considering that the 3% burns if I get some on my fingers, I am afraid to have the 35% in my house. If a child accidentally took a sip of the 3% they would throw up. If someone accidentally took a sip of the 35%, they might die. 



Is 3% hydrogen peroxide harmful to household surfaces?

Answer: It can fade countertops and wood floor over time. I don't know about granite.


3% hydrogen peroxide can fade countertops and wood or dark floors over time so don't let it sit on those surfaces more than 10 minutes. The gray countertop that I have done a zillion experiments on where I let 3% hydrogen peroxide sit for 5 minutes is NOT faded at all. However, there is an area of the countertop next to the kitchen sink that is faded. It is faded because I spray out the kitchen sink with hydrogen peroxide and let it sit. Some of the mist got on the surrounding countertop, and I never wiped it up. After doing that for months, the countertop faded. So, it is okay to let the 3% hydrogen peroxide sit on the sink, bathtub, or shower until it is dry. But wipe it off of other surfaces after 10 minutes so it doesn't fade them. The wood floor around my toilet is also faded. I spray off the toilet every day and some mist falls on that wood floor. It took about a year before the floor started to fade. I've used hydrogen peroxide to clean up dog throw up off the same wood floor. I let it sit for just five minutes and wipe it off. That did not fade the floor at all. 

Does 3% Hydrogen Peroxide kill all types of germs?

Answer: No

I cannot guarantee that hydrogen peroxide will kill ALL bad bacteria and viruses. There are probably plenty of germs that the 3% hydrogen peroxide won't kill. Here is a research paper stating that 3% hydrogen peroxide is good for killing salmonella and e.coli. However, other research shows that it is NOT good for killing norovirus. (That is why I recommend keeping chlorine bleach or the Clorox Hydrogen Peroxide products on hand for emergencies when someone is throwing up. Those products have been tested and proven to kill norovirus surrogates.) 


Can essential oils be added to hydrogen peroxide for cleaning?

Answer: The hydrogen peroxide still kills germs well even with a few drops of oil added. The oils do not mix with hydrogen peroxide. They separate but still make it smell good. 

Many essential oil fans have asked me if a drop of essential oils can be added to the bottle of 3% hydrogen peroxide to make their cleaning smell better. I decided to test it along with the test of how long a bottle of 3% hydrogen peroxide is good. I put about 3 drops of Thieves oil into a new bottle of 3% hydrogen peroxide. I also put about 3 drops of lavender oil into another new bottle of 3% hydrogen peroxide. I also opened a new bottle of hydrogen peroxide, used a little, and put the lid back on. I let these bottles sit for about a month.

Then I did the same experiment that I always do. I made germ water with dirt from the back yard and bacteria scraped from a previous days "dirty hands" plate. I put 1mL of germ water onto each square on my countertop. I rubbed the germ water all around the squares and let them dry. Then I added .5 mL of each product onto the appropriate square. I spread them around to completely cover the square and set a timer for 5 minutes. After 5 minutes, I swabbed each square and rubbed the swabs onto an agar plate. The plates were incubated for 24 hours in my warm incubator.





As you can see, the 1 month old bottles of hydrogen peroxide all did great! The addition of the Thieves and Lavender did not appear to hurt the ability of the hydrogen peroxide to kill germs.




I had also done this experiment a month earlier comparing pure 3% hydrogen peroxide, 3% hydrogen peroxide with a few drops of Thieves oil, and pure Young Living Thieves oil (.5mL of each thing). In this case, the Thieves had only been in the hydrogen peroxide for 18 hours before the experiment. As you can see, the hydrogen peroxide still killed bacteria well even with the Thieves added.




It is important to remember that I kept the caps on tightly the entire time the hydrogen peroxide was stored. So, it might not be good if you leave the cap off all day. I make it a point not to tell people to "mix chemicals". I don't know for sure that no crazy or harmful reaction is taking place between some component of the essential oil and the hydrogen peroxide. However, I didn't die breathing them, and they all still smelled good after a month. So, you can make your own decision about that.


If you would like to suggest an experiment, please post on my facebook page. I also really need to earn money from this website in order to keep doing experiments (agar plates, essential oils, and cleaning products are expensive). If you want to contribute, please use my Amazon affiliate links. Just click on any of my links that go to amazon, and buy whatever you want. You don't have to buy what I recommend or even the product that the link goes to. Here is a link. I'll get a small percentage of the sale and use the money to buy experiment supplies. Thank you.

--Annie Pryor, Ph.D. 
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