What do you think about bleach and molds? Are you also wondering about how bleach kills molds? Well, it’s actually a great concern as the internet contains a lot of misinformation about bleach and mold. A Google search on the relationship between bleach and mold gives conflicting information leaving you without a clear choice.

Some blogs also do the same with others saying that bleach eliminates moulds and others warn against bleach use. Will all the confusing reports, where will you land? That’s why this article is here to answer the question, does bleach kill mold? Please continue reading to understand better.

Does Bleach Kill Mold

Understanding bleach

What’s bleach? It can be termed as a generic term describing numerous chemicals used for various purposes. For instance, lightening hair colours, removing stains, and whitening clothes, among others. It can also sterilize and disinfect bacteria and germs. There are various bleach types, with chlorine as the most common for household use.

Does bleach kill mold?

Every indoor mould growing on surfaces can potentially be killed by bleach. It can get rid of every mould species plus spores, making a surface clean and resistant to other future moulds. It’s mainly effective on non-porous materials- bathtubs, tiles, countertops, and glass. However, it can’t penetrate porous materials such as wood and drywall. That means it’s not effective as it can’t come into contact with the moulds growing on such surfaces. It’ll only get rid of the moulds on top and leave the roots, which will grow back.

Killing mould with bleach

The harsh flames produced by bleach need proper ventilation to keep the environment safer. Putting on gloves to cover the hands is very essential to avoid possible corrosion. Follow the following steps;

Begin by mixing the bleach with water such that one bleach cup for a water gallon.

  • Stir the solution until it’s evenly mixed.
  • Apply the mixture on non-porous surfaces with molds by using either a bucket or spray bottle.
  • You may choose to leave the surface undried for the sake of killing future moulds. If you’ve got children around, it’s crucial that you clean up the solution to avoid any untold dangers.

Now, let’s go back to the question, does bleach really kill mould?  Alright, many mould removal products use sodium hypochlorite as the main ingredient in bleach. But, we’ve got several reasons why we can prefer chlorine bleach alternatives. For instance, we mentioned earlier that bleach can’t penetrate porous materials. For this reason, chlorine can’t penetrate the drywall and wood, however, water would. Unfortunately, the water will be absorbed and provide moisture for the mould to grow even better. Chlorine also becomes ineffective after some time, especially when exposed due to evaporation. It’s the same thing that happens following application on porous surfaces. The water left behind works effectively in providing a cool environment for the growth of more molds. It actually perfectly serves the internal mould spores.

What do you think happens if the moulds are killed, but the roots remain? They’ll obviously sprout again, right? This will only leave you with continuous cycles of bleaching in the name of eliminating moulds. Bleach will possibly multiply mould growth. It happens mainly when mold colonies sense a bleach presence, they picture it as a threat and respond by reproducing at a rapid rate, taking the roots deeper, and increasing the growth rate.  It may be the reason some people believe that spraying bleach on wood will mainly change their color, making it invisible as you think you killed it. You’re likely to be storing a useless bottle thinking it’s still fresh with chlorine bleach.

You should also not forget that bleach is corrosive and harsh. Therefore, it can it can seriously destroy the materials it comes into contact with. When mixed with ammonia, chlorines releases fumes and even produces toxic gasses that can be harmful to the surrounding. We’ve other safer methods that can be used as substitutes. They include borax, vinegar, among others, which aren’t toxic, thus safer for use. It’s, therefore, advisable to use non-bleach products. If situations force you to, then please consider applying it on non-porous surfaces.

Extra alternatives to mold removal

Borax- Using borax for mold killing has various advantages over other products. It may be toxic to your body if swallowed, but it doesn’t release harmful fumes. It’s powdery having a PH of around 9 with lower toxicity. Mainly, it’s used for cleaning toilets and drainages. Other times, it’s utilized as a fungicide, pesticide, or insecticide. Therefore, mixing it with water, the solution formed can kill mold as it naturally inhibits them.

Vinegar– Get white distilled vinegar and fill it in a spray bottle without diluting. Spray on the affected surface before wiping it clean or leaving. Not wiping may be more effective as it clears any possibility of future growth.


Ammonia- It operates almost exactly as bleach by majorly killing molds on non-porous materials. It’s however ineffective in countering those on porous surfaces. It’s also harmful and toxic when used. Learn not to mix ammonia and any bleach as they can be dangerous. The combination results in the production of toxic fumes that are harmful to your health and the environment. Do you know that chlorine mixed with ammonia was used as a weapon during WWII?

Hydrogen peroxide– It plays three roles, including being antibacterial, ant-fungal, and antiviral. It’s among the best chlorine bleach substitutes as it doesn’t danger the environment. It perfectly removes molds on clothes, walls, bathroom fixtures, and floors. Hydrogen peroxide is a clothes bleaching agent, it may as well help remove the stain left by molds. Moe other products acting similarly to hydrogen peroxide are baking soda, laundry detergent and water, tea tree oil, and grapefruit seed extract.

The Bottom Line

Bleach kills any mold types it comes into contact with. It’s very effective, especially on non-porous surfaces, which don’t allow penetration and lack mold growing underneath. However, it doesn’t succeed fully in clearing molds on porous materials like drywall and wood. Another thing is that bleach may be harmful as it produces toxic gasses and dangerous fumes.

It’s essential to consider following the precautions given to avoid corroding your skin and hands when using bleach products. There are other substitutes for use in clearing molds that are natural and effective. Please refer to the article to learn about them.

Also Read: 5 Reasons Why Your Garbage Disposal Is Leaking