Bleach as a Steriliser

I needed to sterilise some swimming equipment and it got me investigating Bleach.
For a number of years we have been encouraged not to use bleach. But I discovered that products like Milton baby bottle steriliser, toilet cleaners and the like are all based on the same product, ie, Bleach!
So, I then searched the Web for sterilising products and the result was unanimously use bleach. But how much to use?
This is where it got interesting, as the amount seems very, very small!
So for sterilising type needs, eg, toilet cleaning, sterilising baby bottle and other food or personal products, 1/4 to 1/2 of a teaspoon in 1Lt of water is sufficient, and even then it only takes 10 minutes, eg, used an empty washing up liquid bottle and squirted where need. In Woolies all the Bleaches are the same concentration, both branded and home brands.
I trialed it in my kitchen sink and toilet, and indeed that appears to be all that is needed, both concentration and duration.
At that level of use, I imagine it’s impact on the environment is small.
Hoping the Choice scientists can confirm this level of use, its safety and impact?


@longinthetooth, you can get the MSDS from here. Type in bleach in the search window on the top left and the homebrand bleach will be in the drop down list as you type ‘bleach’. Click on it then click on it again in the main window on the right.

The MSDS provides base information on safety and environment.

Other brands with the same active ingredients will have similiar information.

Acronyms!! What is the MSDS? The link opens to a login only page? Maybe I’ll be able to understand the significance of your comment then.

The point I am making relates to the advisory aspect of using simple cheap bleach rather than other supposedly purpose made products at a premium, while also taking into account the general advice about not using Bleach, driven I think by environmental grounds. I’m a supporter of precautionary approach to the environment, but recognise the safety need to steralise.

Sorry about the acronym, Material Safety Data Sheet.

If you can’t access the ones in the link above, you can google ‘MSDS bleach’ to find others.

Wikipedia also has some useful information as well.

When we purchase some things, we look at active ingredients and their concentrations, then calculate which brand is cheapest based in the unit of active ingredient.

You may be surprised what other common cleaning products have the same active ingredients under different brands, with different concentrations and prices. Maybe there is opportunity for someone to produce a app that does the calculation more easily to work out cheapest per unit of chemical/active ingredient.


Remember that bleach is also a way to sterilise drinking water. Check the EPA’s advice here.

If you are thinking of using it for baby bottles or teats, be aware that it converts to salt (sodium chloride) which is not nice for little kidneys, so be sure the bottle and teat are drip dry, and understand the solution only works for a very limited period…

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To sterilise you need to subject your object to 132degrees centigrade for 7 minutes in a pressure chamber. Chemicals do not sterilise.
I think that bleach just does that, bleach. It only changes the colour of the critters from black.

Much as I like the idea of “natural” agents for jobs like this, I have found that bleach is both effective and of long history as a disinfecting agent. I tried so called natural alternatives to get rid of mould in the bathroom - and all they seemed to do was get rid of my money (they were expensive). Bleach does get rid of mould, and mould is very unhealthy for you.
Providing you drain the bottles etc after using the bleach solution, there will be little toxicity, because bleach breaks down fairly quickly into less harmful agaents.

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I raised this here with Choice, as this needs more than just opinion. It requires science. If it was only about it whitening effect, IMO it wouldn’t be the health additive to swimming pools? Clearly no one is going to use a high temperature pressure container, but some things do require more than a quick flick with a damp cloth!
But, the main aspects of me raising this is, bleach is often an ingredient in cleaning products, eg, toilet cleaners and baby product cleaners like Milton. Secondly, from my reading about its use in sterilising, the amount required and the exposure time is very small. So, unlike a full squirt of toilet cleaner, it seems one needs just 1/2 teaspoon diluted in 1lt water. So, one gets the safety benefit, but also minimises the impact on the environment by reducing the amount going into the sewers and then into water sources., etc.
But, it needs Choice scientists to comment, rather than mere lay people like me!

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Bleach does sterilise. Sterlise/sterlisation is ‘the procedure of making some object free of live bacteria or other microorganisms (usually by heat or chemical means’.

Bleach kills micro-organisms or making something, if the concentration is high enough, something free of living microbes. ‘The broad-spectrum effectiveness of bleach, particularly sodium hypochlorite, is owed to the nature of its chemical reactivity with microbes. Rather than acting in an inhibitory or toxic fashion in the manner of antibiotics, bleach quickly reacts with microbial cells to irreversibly denature and destroy many pathogens’.

Sodium Hypochlorite is also used as a food sterilising agent. For example, processed lettuce for fast food outlets or prepackaged salad greens is treated generally with Sodium Hypochlorite or Calcium Hypochlorite to kill any pathogens which may affect human health. It is not possible to use heat treatments as the lettuce/salad greens would be unsalable.

Bleaches is also a strong oxidising agent which denatures organic dyes and bleaches, causing them to become colourless through the chemical reaction with the chloride ions.

Heat and pressure can also have the same sterilising effect as bleach. Heat and pressure however doesn’t have the same colour bleaching effect.

Weak solutions of bleach on mould impregnated materials may only kill and bleach the surface mould and not the mould hyphae which will be growing within the underlying material. If the bleach does not have direct contact with the living organism, it won’t die. This is why mould in gyprock or in mortor between bathroom tiles will reappear after a bleach treatment, if the mould has grown into the underlying strata.


Thanks for the info.

Hi @longinthetooth,
Thanks for starting this interesting topic and to everyone who has left a reply. You might find @JemmaCastle’s story on chemicals in cleaners of interest. We also review a variety of different cleaning products (about a third of which contain bleach).

When used correctly, household bleach is safe and breaks down quickly keeping the environment safe. However, make a mistake and it can be dangerous. Personally, when it comes to sterilisation, I opt for boiling water or steam cleaning equipment as it’s easier and a bit more pleasant on the nose.


@phb @trevor3
Trevor is technically correct. Bleach is not considered as being able to sterilise a product, it is only a disinfectant. There is a subtle difference here but it is important. To sterilise something you need to kill all organisms present (this includes viruses, bacteria, bacterial spores and fungi) but to disinfect you only have to remove most harmful organisms. (See table at (and the majority of chemicals) are only disinfectants as they are unable to kill all types of organism effectively. For example bacterial spores are often not killed by chemicals except at extreme concentrations. Most people use the terms sterilise and disinfect interchangeably but they do mean different things.
While bleach is effective, the overall effectiveness is affected by a number of factors including;

  • Acidity of the solution (not generally a consideration in household use)
  • The amount of organic material present (particularly proteins like blood) as bleach reacts with this material in doing its job and is quickly consumed from the cleaning solution and thus the solution loses effectiveness.
  • It evaporates from the solution and therefore needs to be replaced daily.
    A good discussion of this is available at

Based on the information in the Oregon University fact sheet you would need about 100ml bleach in 1 litre to create a generally effective disinfecting solution for surface disinfection use. This is based on buying a 5% solution of bleach. It is important to be aware that the % bleach in a bottle you purchase is probably greater than the stated % when you buy it in the sealed bottle but the % will drop over time while stored in your cupboard. This is generally why bleach has a ‘use by’ date on it. The manufacturer has calculated that the % bleach will be at least the stated level up until this date.


The other major factor that affects the potency of bleach as a disinfectant, mould remover, etc., is that in most commercial bleach solutions they contain a surface active agent (watch them froth when agitated in water) that helps penetrate the bacterial or fungal cell wall, where a plain solution of Sodium Hypochlorite (bleach) [Milton has no surface active agent], might be ineffective. The surface active agent is usually what is called a non-ionic surface active agent that does not inhibit the actions of the main ingredient Sodium hypochlorite. Commercial bleaches may also contain stabiliser agents to prevent excessive loss of potency during storage. Not all bleaches are created equally.

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This highly technical blurb about Sterilisation vs disinfectant isn’t really the topic I raised.
In layman’s terms I have referred to the type of applications, eg, making swimming gear, toilets and baby bottles safer to use.
That although many products give the allusion that they are something special, in fact most are merely bleach!
Additionally we are told to avoid bleach for such purposes as it is harmful to the environment.
Further that that there is virtually no way a layman would know they are probably using a lot more than needed to do the job, and in doing so are inadvertently harming our sewers and hence environment.
That probably it would be better to merely use cheap bleach in the appropriate dilution, if only Choice would help or guide us us with some science based info!

As I said in my original post an effective surface disinfection solution is about 100ml in 1 litre. The 1/4 to 1/2 teaspoon in 1 litre you outline would be of next to no effect. There is just not enough hypochlorite (active ingredient of bleach) to have any meaningful level of interaction with potentially harmful organisms.
But I do agree with you that there is absolutely no need to pick a brand name bleach to achieve a good outcome. @tmar5954 is right though that some products do contain extra additives (e.g detergents) that improve the effectiveness of the product under specific circumstances. But as far as ‘killing’ power goes the only consideration is the concentration of bleach in the product. Same concentration = same effectiveness.

From what the cleaner at the office tells me is that the only difference between brands of chlorine is the smell.
The cheap brands are unpleasant to work with because of this. Other than that bleach is bleach.

However you just need to be aware that bleach removes the colour of mould, so the black is gone and you get a warm fuzzy feeling that you have done a good job. but the mould is still there, you just cannot see it.

If you want to do a good job use your grandma’s old pressure cooker and boil what ever you want cleaned. No need to place the weight valve in place, just boil hard. (The higher the pressure in a vessel the higher the temperature of the boiling water) No nasty chemicals.

Hi @jyrn.

Sorry to be picky, but bleach is a sterilising agent. Even the links that you have provided indicate and report such, namely…

'Chemical sterilization – Chemicals like Ethylene oxide, Ozone, Bleach, Glutaraldehyde and Formaldehyde, Phthalaldehyde, Hydrogen Peroxide, Dry…"

Sodium hypochlorites (the active ingredient of bleach) is also an approved for the food industry to sterilise high risk foods such as fresh salad greens. Such high risk foods have potential to contain pathogens or their propagules which may impact on human health…these include bugs which cause gastro type infections/disease.

I find this topic interesting in that 40 or more years ago, every housewife would have known the answer to the original question. So much that was once common knowledge has been lost. People throw out milk and other food as soon as the Used By Date arrives, in the belief that it will be bad for you, regardless of its condition. TV ads encourage us to buy products that kill “99.9% of germs”, and spray half the house with them in case the baby gets a germ while sitting on the floor.
A few years ago the Austin Hospital in Melbourne found that bugs were becoming resistant to the special cleaning products that they used throughout the buildings. So they conducted a trial using the old method of bleach and water, and it worked well - and was much cheaper. Surprise, surprise.

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Lots of good, accurate info here. The only thing not mentioned was when I looked at my liquid bleaches the other active ingredient was sodium hydroxide a.k.a. Caustic soda. So be wary about how you use it. Sodium hydroxide, apart from being very corrosive to skin and other tissue, can react quite violently with acids. I use bleach for cleaning the shower base & toilet ect. But would never consider it for anything I might come into contact with my body. Cheers.