Skip to main content

How Bleach Works: Disinfection, Stain Removal, and Dangers

Linda Crampton has an honors degree in biology. She has taught high school biology, chemistry, and physics as well as middle school science.

The fading colour of a flower is a symbolic representation of bleach in action.

The fading colour of a flower is a symbolic representation of bleach in action.

A Versatile Household Product

Bleach is a multipurpose product that is very useful in homes, hospitals, science laboratories, and industry. At the correct concentration, it's a potent germ killer. It can also whiten and brighten fabrics and remove stains. Some people even use it to create special effects in their art projects.

Several chemicals can act as bleaches. The most commonly used one is sodium hypochlorite, or NaOCl. (The formula is also written as NaClO.) Sodium hypochlorite dissolved in water is sometimes known as chlorine bleach. It destroys a wide range of bacteria, algae, fungi, and viruses.

Other hypochlorites can also act as bleaches, including calcium hypochlorite. This is sold as bleaching powder. Some chemicals that don't belong to the hypochlorite family are bleaches as well, including hydrogen peroxide and sodium perborate. This article focuses on sodium hypochlorite in water, which is easily obtainable and widely used. It's a very helpful product, but it must be used with caution since it's potentially dangerous. The concentration of a bleach product is an important factor to consider with respect to both effectiveness and safety.

The fact that sunlight can act as a bleach has been known for a long time.

The fact that sunlight can act as a bleach has been known for a long time.

The History of Bleaches

The discovery that sunlight can bleach fabrics is a very ancient one. The ultraviolet radiation in sunlight is responsible for the colour fading. Like chemical bleaches, UV light also kills germs if it's sufficiently intense.

The discovery of chemical bleaches was based on the work of three scientists in the eighteenth and nineteenth centuries.

  • A Swedish scientist named Carl Wilhelm Scheele discovered chlorine. (This is significant because sodium hypochlorite contains chlorine.)
  • A French scientist named Claude Berthollet discovered that chlorine could bleach fabrics. He was also the first person to make a solution of sodium hypochlorite, which he called "Eau de Javel" or Javel water. The name came from the part of Paris in which Berthollet worked.
  • Antoine Germain Labarraque, another French scientist, discovered that hypochlorites could act as disinfectants.
Laundry bleach brightens white fabrics.

Laundry bleach brightens white fabrics.

Sodium Hypochlorite

Sodium hypochlorite is a white powder in its pure form. The bleach that is bought in stores contains sodium hypochlorite dissolved in water. It's a clear solution with a slightly yellow colour. Household bleach that is intended to be used for disinfection generally contains about 5.25% sodium hypochlorite by weight, although one brand in my local supermarket contains 7.4%.

Sodium hypochlorite is a very unstable substance and reacts chemically with the water in the bleach container. A variety of reactions may occur, but the most common ones are described below.

Production of Hypochlorous Acid

The reaction between NaOCl and water produces produces HOCl, or hypochlorous acid, and sodium hydroxide, or caustic soda, as shown in the following chemical equation.

NaOCl + H2O → HOCl + NaOH

Hypochlorous acid is responsible for bleach's ability to remove colour from objects and for its ability to disinfect surfaces.

Production of the Hypochlorite Ion and Oxygen

The NaOCl also breaks down to produce the hypochlorite ion, or OCl-. This ion decomposes into a very reactive form of oxygen and a chloride ion. Like hypochlorous acid, the oxygen can remove colour from items, but to a lesser extent.

Removing Colour with Bleach in an Art Project


If you intend to use bleach for art projects, make sure that you use the safest concentration possible. The substance should be kept out of reach of children and pets, and the area should be well ventilated. It would be a good idea for the artist to wear gloves.

How Does Bleach Whiten Fabrics?

Sodium hypochlorite is classified as an oxidizing agent. An oxidizing agent takes electrons from other chemicals when it reacts with them. Using its oxidizing ability, NaOCl (or the HOCl that it produces) breaks chemical bonds inside chromophores, which are the parts of molecules that give them colour. This causes the chromophores to either change their bonding structure or to break up. The ability of the chromophores to absorb and reflect light is altered and they are unable to produce colour. In this way, the NaOCl removes stains from fabrics and also lightens their overall colour.

Bleach can be very useful in the kitchen.

Bleach can be very useful in the kitchen.

How Does Bleach Kill Germs?

Sodium hypochlorite reacts with proteins in microbes, denaturing them, or changing their shape. A protein is made of one or more chains of amino acids. Each chain is twisted and folded into a specific shape. If the shape changes, the protein can no longer do its job.

The hypochlorous acid that forms when sodium hypochlorite reacts with water causes microbe proteins to denature and then clump together, forming a non-functional mass. This destroys the microbes and some visible life forms. The substance can be good for removing bacteria, viruses. mold, and algae when used externally. Bleach can also denature our proteins, however, which is why safety precautions are needed when we use the substance.

Antibacterial Action of Bleach

The Importance of Dilution

Bleach that is bought in stores for cleaning and disinfecting needs to be diluted with water before use. The dilution factor depends on the starting concentration of the product. It's important to look at the container to see the manufacturer's recommendations. The company's website should be a good resource for dilution recipes for different uses and for cleaning suggestions. The CDC and Michigan State University references below also contain dilution instructions. The idea is to weaken the bleach so that it's safe and economical to use but not to the extent that it's no longer effective for a particular purpose.

Diluted bleach will only be effective for about a day (twenty-four hours) or sometimes for an even shorter time. Even the undiluted product has a shelf life and will eventually become ineffective. Once the NaOCl has finished reacting, salt (NaCl) and water are left. The container's "use by" date should be noted. This date is not a guarantee of the bleach's safety, though. Since we can't see the chemicals in a container of bleach, we don't know when they've finished reacting.

Be Careful

When diluting bleach and using it for cleaning items, it's important to work in a well-ventilated area. The vapour may irritate the eyes and airways. Protective gloves should be worn. Diluted solutions may be mildly irritating. Concentrated solutions can burn. Bleach mustn't be ingested and can be very dangerous if it is.

There are lots of uses for bleach in a bathroom.

There are lots of uses for bleach in a bathroom.

A Disinfectant and a Cleanser

Bleach is an excellent germ killer and can be very helpful in a home. For example, bleach can:

  • remove mold and mildew from bathroom tiles and shower curtains
  • clean shower mats
  • clean porcelain toilets (but make sure that you read the "Potential Dangers" section below before you do this)
  • remove plants from cracks in a driveway or path
  • clean concrete
  • clean surfaces on which raw foods have been placed, such as cutting boards
  • clean kitchen counters, refrigerators, stoves, and floors
  • disinfect door handles, toilet flushers, faucets, sinks, garbage cans, and non-porous toys
  • disinfect pet areas, such as litter trays and bird cages
  • disinfect garden tools to prevent spreading an infection from one plant to another
  • act as a cut flower preservative

Different concentrations of bleach may be needed for different jobs. It’s important to do some research to find an appropriate and safe concentration for each of the tasks listed above.

Bleach is useful for cleaning bathroom tiles. The correct product concentration is important, however. Safety and effectiveness need to be combined.

Bleach is useful for cleaning bathroom tiles. The correct product concentration is important, however. Safety and effectiveness need to be combined.


If instructions say to dilute bleach to a 1:100 solution (for example), they generally mean that one part of bleach should be mixed with ninety-nine parts of water. Occasionally, the ratio is used in a different way. The situation should be investigated if confusion exists. Dilution recipes for specific purposes are available from a product’s manufacturer or from a health agency.

A Germ Killer on External Surfaces

If bleach is being bought specifically to kill germs, the bottle label should be read carefully. The more concentrated solutions should have a word like "disinfectant" on the label. The less concentrated solutions are used as laundry bleaches and may not be able to kill germs.

The term "germ" means microorganism or microbe. Unexpired bleach destroys some viruses (including coronaviruses) as well as bacteria when used properly on exterior surfaces. Viruses have some unusual features and aren't considered to be living entities by everyone. Regardless of how they are classified, they can have some major effects.

Bleach that is being used to disinfect a surface should be left in contact with the item for at least five minutes according to most recommendations (or ten minutes for some microbes) before being rinsed off. The surface should then be allowed to air dry whenever possible. It's important to think about the materials that are used to rinse or dry an item after it's been sanitized with bleach. If a contaminated cloth is used, it will re-introduce germs to the area.

Unexpired household bleach will be effective against coronaviruses when properly diluted. Follow manufacturer’s instructions for application and proper ventilation. Never mix household bleach with ammonia or any other cleanser.

— Centers for Disease Control and Prevention (CDC)

Sodium hypochlorite is used as a disinfectant in some swimming pools.

Sodium hypochlorite is used as a disinfectant in some swimming pools.

Sodium Hypochlorite in Water and Pools

The safety of bleach is related to its concentration. Sodium hypochlorite is often used to disinfect drinking water and swimming pool water. When some people hear this, they think that they drink or swim in bleach. In fact, they do, since bleach is simply sodium hypochlorite dissolved in water. The concentration of NaOCl is kept to a safe level in water that's designed for human use, however.

Investigate When Necessary

Online research or queries submitted to local authorities or personnel should tell you what disinfection process is used in your local tap and swimming pool water.

Laundry Bleach

Bleach can also be useful when doing the laundry. The product can be added to detergent to clean and brighten white fabrics or the fabrics can be soaked in bleach to remove a stain.

The washing instructions on a fabric and the instructions on the bottle of bleach should be followed carefully. The labels on some bleach containers say that the product is safe for certain types of colourfast fabrics, but it may be advisable to test the product on a small, hidden area of the fabric first.

Bleach may also weaken the material used to make an item of clothing if it's used over a long period of time. Some laundry bleaches contain an additive ("Fiber Guard" or an equivalent substance) to protect fabrics and keep them strong.

Hydrogen peroxide is usually a better bleach for coloured fabrics than sodium hypochlorite because it's less likely to remove the colour.

Hydrogen peroxide is usually a better bleach for coloured fabrics than sodium hypochlorite because it's less likely to remove the colour.

Potential Dangers of Bleach

Sodium hypochlorite is very reactive, so it's essential to take safety precautions, even with diluted bleach. The product must be kept in a firmly closed container which is labelled carefully and kept out of reach of children and pets.

Some of the potential dangers of NaOCl are listed below.

  • When NaOCl reacts with light it produces dangerous chlorine gas (Cl2). Chorine is also made when the solution is heated. Even at room temperature, some chlorine escapes from the solution.
  • The caustic soda (NaOH) in bleach can irritate or burn skin, depending on its concentration.
  • Bleach is corrosive, especially at higher concentrations.
  • Bleach and cleansers containing ammonia must never be mixed. They react to produce a dangerous gas that contains toxic chloramine. The bleach must also be kept away from acids (including vinegar), rust remover, and toilet bowl cleaner.

If safety precautions are followed, bleach is a great substance to have in a home. It improves the appearance of fabrics, cleans surfaces, and can be an excellent germ killer. Even hospitals use the product to kill dangerous microbes. It's an impressive liquid.


  • A chemistry professor at the University of Bristol describes sodium hypochlorite.
  • Cleaning and sanitizing your home with bleach from the CDC
  • Bleach product information and dilution recipes for different purposes from Michigan State University (This site also discusses bleach in reference to COVID-19.)
  • Chlorine bleach safety information is discussed by North Dakota State University

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Questions & Answers

Question: My front-loading washing machine has three compartments for detergent, bleach, and softener. Can I put sodium hypochlorite directly into a compartment without diluting it? If yes, how much can I put in for a 5kg white bed sheet? If no, what is the mixing ratio between water and sodium hypochlorite before putting the liquid in the bleach compartment?

Answer: You need to look at the instruction booklet for your washing machine and the label on your bottle of bleach to find the information that you seek. The booklet will probably give you information about putting bleach in your machine. The dilution factor required for your bleach–if it needs to be diluted—will probably be written on the bottle. The required dilution depends on the starting concentration of the product. Since I don’t know the starting concentration of your brand of bleach, I can’t tell you how much dilution is required. If the sodium hypochlorite bleach that you have is concentrated, please remember to be careful when using it!

Question: Is it safe to use bleach to clean cookware?

Answer: In general, no. The bleach can damage the surface of some pots and pans and may cause the production of dangerous gas. You should read the manufacturer’s instructions for your pot or pan, however. They may state that bleach is safe for the material and/or coating that they used to make the cookware and give dilution instructions for the bleach. If this information isn’t provided, don’t use bleach to clean the cookware.

You could email the manufacturer to ask them if it's safe to use bleach if you can't find the leaflet that came with your cookware or if the manufacturer doesn't provide the information in the leaflet or on their website. If you discover that it is safe to use bleach on your brand and model of cookware, follow the dilution and safety instructions carefully and rinse the container thoroughly after using the bleach.

© 2013 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on March 22, 2019:

Thanks for the comment, Rishi. I'm glad the article helped you.

Rishi on March 21, 2019:

Hi, I'm doing a chem project and this was very helpful

Linda Crampton (author) from British Columbia, Canada on March 12, 2019:

Dilution factor and dilution ratio are not the same thing, which is how the confusion arises.

The dilution factor is the final volume divided by the initial volume. If we placed 1 ml of solute (the initial volume) in 9 ml of diluent, the finale volume would be 10 ml and the dilution factor would be 10. Unfortunately, this is sometimes described as a 1:10 solution. This is confusing because most people assume that the : is a ratio sign. In this case, however, it means one out of ten parts is the solute and the other nine parts are the diluent.

If we state that the dilution ratio is 1:10 instead of the dilution factor, then we mean that 1 part of solute is mixed with 10 parts of diluent.

The most important thing is to follow the dilution instructions for a particular product given by the product’s manufacturer or a health agency. If this is done, we don’t we don’t have to worry about whether the recipe they’ve given is determined by a dilution factor or a dilution ratio.

HypochlorousMan on March 12, 2019:

I thought a 1:10 bleach mixing ratio means 1 part 'bleach' to 10 parts 'water'; like a 1:1 ratio is 1 part 'bleach' to 1 part 'water'.

Linda Crampton (author) from British Columbia, Canada on December 09, 2014:

Hi, Alun. I agree. Learning about the chemistry of substances and materials that we encounter every day could bring science to life! Thank you very much for the comment.

Greensleeves Hubs from Essex, UK on December 09, 2014:

Comprehensive article on all things connected with bleach, including of course the science, Linda. It occurs to me that the application of science to such seemingly mundane household products as bleach is a great way of teaching how science - in this case molecules and chemical reactions - has practical applications for us all.

And for some who have never had an interest in chemistry because they don't see how it directly affects them, it may bring the subject to life.

Linda Crampton (author) from British Columbia, Canada on October 17, 2013:

Thank you very much, Crafty! I appreciate your comment.

CraftytotheCore on October 17, 2013:

Such interesting facts about bleach! I had no idea it can act as a cut flower preservative or be used in art. Amazing!

Linda Crampton (author) from British Columbia, Canada on September 19, 2013:

Thanks for the visit and the comment, DDE.

Devika Primić from Dubrovnik, Croatia on September 19, 2013:

How Bleach Works - Disinfection and Stain Removal a well advised article on this topic and you have informed us to the point and shared the simple ways of how bleach works and what it is used for in other circumstances .

Linda Crampton (author) from British Columbia, Canada on August 26, 2013:

Thank you very much for the comment, Pamela.

Pamela Oglesby from Sunny Florida on August 26, 2013:

I have always used bleach to do a lot of cleaning and with laundry. You still listed several facts that I didn't know. Very useful hub.

Linda Crampton (author) from British Columbia, Canada on August 23, 2013:

Your housekeeper sounds like a wise person, drbj! Thanks for the visit and the comment.

Linda Crampton (author) from British Columbia, Canada on August 23, 2013:

Hi, Dianna. Bleach can be amazingly useful! People often think of it as a simple substance, but it's really very helpful. Thanks for the comment and for sharing the information.

drbj and sherry from south Florida on August 23, 2013:

Alicia - My housekeeper once told me, "... if you ain't cleanin' with bleach, you ain't cleanin'." She must have read your hub. :)

Dianna Mendez on August 23, 2013:

As a former child care director, we used bleach regularly to disinfect just about every inch of the place. It is especially useful during cold season. Great post, as always!

Linda Crampton (author) from British Columbia, Canada on August 23, 2013:

Thanks for the comment and for emphasizing the potential dangers of bleach, Laura!

Laura Deibel from Aurora, CO on August 23, 2013:

Interesting hub and appropriate videos. I have tended to avoid bleach because to me it stinks, but I also, I had a mishap with bleach cleaner plus ammonia cleaner reacting! For this reason, it is wise to CAREFULLY read all the ingredients in your cleaners. Thanks!

Linda Crampton (author) from British Columbia, Canada on August 20, 2013:

Thank you, Deb. I appreciate your comment.

Deb Hirt from Stillwater, OK on August 20, 2013:

Bleach is one of the best things made available to us, but like you say, it must be used properly. A great article for such a simple cleaner/disinfectant.

Linda Crampton (author) from British Columbia, Canada on August 20, 2013:

Thanks for the visit and the comment, Eddy.

Eiddwen from Wales on August 20, 2013:

Interesting and useful Alicia; thanks for sharing.


Linda Crampton (author) from British Columbia, Canada on August 18, 2013:

Thank you for sharing your experience - which a great warning for us all - and thanks for the vote, too, moonlake!

moonlake from America on August 18, 2013:

I use bleach and cleaned my bathroom with it yesterday. Later when I took my sweat pants off I found a big white print on the back of my sweats. I must have wiped my hand on my pants. I just have to learn not to wear good clothes while handling bleach. Voted up on your hub.

Linda Crampton (author) from British Columbia, Canada on August 18, 2013:

Thank you very much for commenting and for the vote and the share, Bill. I hope you have a great week, too!

Bill De Giulio from Massachusetts on August 18, 2013:

Hi Linda. What a fascinating read on something that we use day in and day out. I never stopped to think exactly how does bleach work. Thank you for the great explanation that even I can understand. Great job. Voted up, shared, etc... Have a great week.

Linda Crampton (author) from British Columbia, Canada on August 18, 2013:

Thank you very much, havingmysay.

havingmysay from USA on August 18, 2013:

Thanks for responding AliciaC! Yes, it is quite scary after reading all about such a powerful solution and then considering that people actually let it seep into their skin...on purpose! Thanks again for your research!

Linda Crampton (author) from British Columbia, Canada on August 18, 2013:

Thanks for the visit and the comment, havingmysay. I've read claims that bleach has helped some people's ringworm, but I've never seen any scientific research about this idea. The thought of deliberately putting bleach on the skin is scary! The effects can range from an irritation to a serious burn.

Linda Crampton (author) from British Columbia, Canada on August 18, 2013:

Thank you very much for the comment, the vote and the shares, Sue! I appreciate them all.

havingmysay from USA on August 18, 2013:

That was a very informative hub on bleach. I know there were many times when I was younger when I ruined clothes of mine with its splatter or had to run out the room because I used too much when cleaning. One question, I once heard (or read-I can't remember) that you can kill ringworm by taking a bleach-filled swab and placing it on the area of your skin. While this was not recommended, in your research is that possible?

Susan Bailey from South Yorkshire, UK on August 18, 2013:

I love bleach; I use it all the time Alicia. I never even thought about the 'mechanics' of it so this was very interesting to me. Voted up and interesting and shared and pinned. Thank you

Linda Crampton (author) from British Columbia, Canada on August 17, 2013:

Thank you very much for the A+, Bill. I appreciate it!! Yes, I'm enjoying the summer very much. There's been so much good weather this year. I hope you enjoy the rest of the weekend.

Bill Holland from Olympia, WA on August 17, 2013:

Having taught science for a number of years, I give you an A+ for your report. :) Good job Alicia. I hope you are enjoying this beautiful summer we are having.