Victoria Malloy is a Toronto-based freelance writer covering a range of topics with a focus on sustainability. Her work has appeared on Coveteur, The Zoe Report, Well + Good, Apartment Therapy, Natural Habitat and more.
October 17, 2022
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While we may not be considering it in our day-to-day lives, mold is everywhere. Researchers have identified over 100,000 species of mold so far, and we’re routinely exposed to hundreds of them as we go about our daily lives. Mold is ever-present in nature and in the air we breathe, so it inevitably finds its way into our homes. Luckily, the best natural mold killers can help remove existing mold and prevent more from growing.
Many people believe that, unless they have a water intrusion in the home, they won’t have to worry about mold—when, in fact, it requires very little water for mold to grow. Studies estimate that 30 to 50% of all structures have damp conditions optimal for the growth and buildup of biological pollutants, such as mold. In warm, moist climates, this percentage is likely to be higher. In other words, there are a few unsuspecting places mold could be hiding in your home.
According to certified mold mitigation expert and host of The Toxic Mold Podcast Steve Worsley, there’s no such thing as a “mold-proof” home. Mold and mildew sightings are common between shower tiles, on the caulking around the bathtub, and under the kitchen sink. We’ve all tried to tackle these stains with bleach, but just how effective is that? And surely there are less toxic ways to spot-treat mold.
Read on to explore how to best control mold growth and to find our picks for the best natural mold killers.
First things first.
When it comes to a small, one-off case of mold on a nonporous surface (porcelain, glass, etc.), you can pretty easily treat the mold without much cause for concern. But for more extensive contamination (including mold growth on porous surfaces such as drywall and grout, you will need to seek help from a professional to ensure a safe and thorough removal. The Environmental Protection Agency1 recommends that you hire an expert for any mold growth that covers an area larger than 10 square feet.
According to Lauren Tessier, a naturopathic physician specializing in mold-related illnesses, there’s a distinction to be made between ‘killing’ mold and ‘removing’ it. “When people think of remediation, or cleaning of moldy spaces, they often think of simply killing the mold or fungus,” explains Tessier. “When remediating, it is more important to focus on the concept of physically removing the mold, and the moldy contents from the space, rather than just simply killing it.”
If you’re using a fungicide, there may be instances in which the mold (and spores) survive the fungicide. “Stressing a mold by applying a fungicide can cause it to initiate its natural defenses,” says Tessier. These defenses, depending on the species, could be poisonous mycotoxins released as spores into the air.
And when you do successfully kill mold, it’s crucial to remove all traces of the mold thereafter. “Dead mold is dangerous mold,” says Tessier. “Any mold fragments that are left behind after fungicide use can harbor mycotoxins, which can result in local irritation and even severe allergies,” she adds.
How to prevent mold from growing in the first place.
The most ideal solution to mold is not having any, right? On his podcast, Worsley is quick to highlight moisture as the most destructive home offender and says that the key to controlling mold is controlling moisture. If the humidity level is above 50% and you have organic debris as a food source (dust, dirt, etc.), mold is likely to grow. So, a good place to start is by monitoring humidity levels in your home.
Because we know mold can release spores into the air, an air purifier can be a wise investment to help enhance air quality by destroying pollutants such as bacteria, mold spores, and volatile organic compounds through a process of oxidation.
Always use the exhaust fan in the bathroom when showering to eliminate moisture from the room.
Can bleach actually kill mold?
While bleach does a great job of killing live molds, according to Tessier, it leaves behind two things that can serve as a wonderful growth medium for future molds: dead mold fragments and water. “Many people don’t realize that once the active chemical in bleach (chlorine) evaporates, you are left with water, which is integral to mold’s growth and survival,” she explains.
So, while bleach can be a great fungicide for nonporous surfaces, it is not a good fungicide for porous surfaces because they can’t be rinsed, scrubbed, and thoroughly dried. Instead, these surfaces can trap the mold fragments and water, possibly harboring ideal growing conditions for the next round of mold. Tessier stresses that if someone uses bleach to clean mold, that person could be on the receiving end of a double dose of toxicity, through exposure to mycotoxins and toxic chlorine.
How to find the best natural mold solutions.
When seeking a more natural solution for ridding your home of mold, many people favor a thyme-based fungicide, with studies demonstrating its effectiveness in suppressing mold growth in damp dwellings. However, Tessier cautions that these can be irritating to mucous membranes and can pose a risk to people who are chemically sensitive. It’s important to remember that, while better for the environment, natural products do not always ensure safety.
Other antifungal agents, including vinegar and tea tree oil, have shown promise in combating mold.
Studies2 have indicated that vinegar (4.0% to 4.2% acetic acid) inhibited the growth and sporulation of one species but not the other, while tea tree oil was shown to inhibit the growth of both species. This raises the question: Could a 10% acetic acid be that much more effective? While it seems logical, there is insufficient evidence to prove it.
Tessier prefers the use of hydrogen peroxide (3% acetic acid) for its ability to kill mold without the toxic risk imposed by chlorine exposure. Hydrogen peroxide also bubbles when it is put into contact with living substances, which helps let you know it’s doing its job. The downfall, according to Tessier, is that spores can still survive peroxide application, and it does leave behind water and mold fragments (similar to bleach).
Per Tessier, a growing body of research suggests that a higher concentration of hydrogen peroxide, applied over a longer period of time, can potentially induce more fungicidal activity. However, there are some molds/fungi that are more susceptible to this (and other) fungicidal interventions.
How we picked:
As always, we prioritized the most environmentally friendly products when selecting the best natural mold killers. Natural mold killers should not have any chemical ingredients. Each of our picks is nontoxic.
We interviewed several experts on the topic of mold to learn more about what to look for in a natural mold killer and took their input into account when selecting these products.
Mold killers should not only kill mold but also help prevent the regrowth of mold in the future. We looked for products that will be preventive, too.
We chose products that have scientific studies and laboratory tests to back their efficacy.
Our picks for the best natural mold killers:
- Made with tea tree, lemon, and thyme essential oils
- Environmentally friendly
- Just add water
- Can pose a risk to people who are chemically sensitive
- Not proven effective on all types of fungi
- Essential oils may be less effective diluted in water
Primary active ingredient: 10% acetic acid
Product type: Concentrate
When applied directly in concentrated form, tea tree and thyme essential oils have been shown to inhibit the growth of certain types of fungi. This solution is meant to be diluted in water so may not be quite as effective, but it is still a great product to have on hand. To use, you’ll just need to fill the supplied bottle with water and oil drops, as directed in the instructions included. Then, simply spray it on your shower curtain or other surfaces to keep mold at bay.
- Double the strength of regular vinegar
- Comes in a spray bottle format
- Not proven effective on all species of fungi
- Strong vinegar smell
Primary active ingredient: 10% acetic acid
Product type: Concentrate
For a greener, more natural alternative, this cleaning vinegar is a surprisingly powerful formula. It uses 10% acetic acid, which is double the amount of white vinegar. It’s actually safe to consume, too, so you don’t have to worry about using it on kitchen surfaces and can even use it to remove stains from items like coffee pots and tea kettles.
That said, while this is an impactful, healthier solution, it won’t be effective against all mold strains, so if you are dealing with a larger issue, it is still best to consult a professional. Because this is a vinegar solution, you’ll also want to spot-test it before applying it to large surfaces.
- Made from botanical essential oils
- Environmentally certified
- No rinsing or wiping required
- Can be irritating to mucous membranes
- Can pose a risk to people who are chemically sensitive
Primary active ingredient: Thymol
Product type: Spray
Widely used by mold remediation experts and restoration technicians, this fungicide is best used as a wipe application to remove surface mold and as a spray after remediation is complete to control any remaining mold. While most other disinfectants require at least 10 minutes to be effective, this formula takes only 30 seconds to get the job done. The key ingredient here is Thymol, which is a component of thyme oil. The brand prides itself on authenticity and formulates its climate-friendly products with whole essential plant oils rather than synthesized copies.
There are no synthetic fragrances, dyes, or bleach, but it does have a light scent that some Amazon reviewers describe as “musty.” That said, the feedback is overwhelmingly positive, and the product has a 4.7 out of five-star rating overall, with nearly 2,000 perfect ratings.
- Bubbles when in contact with living microbes
- Higher concentrations may offer even more fungicidal activity
- Gray water safe
- May damage certain surfaces
Primary active ingredient: 3% hydrogen peroxide
Product type: Solution
A natural alternative to bleach, hydrogen peroxide is just water with an extra oxygen molecule—but that extra molecule is incredibly powerful. It oxidizes the solution, giving it an antimicrobial and fungicidal power. On the downside, you need to be careful when using this on certain surfaces, as it could damage some materials. Make sure to do a spot test first!
This natural mold killer is completely free of toxic stabilizers and leaves no residue behind. The formula is biodegradable and is actually beneficial to the environment due to its oxygen-enhancing capabilities. In addition to relying on this for its mold-fighting benefits, you can also use it to remove stains on laundry, wash your foods (fruit, veggies, nuts, seeds, and grains), and even for first aid purposes on your throat, mouth, and ears—that’s how safe the ingredients are.
- Tracks indoor air quality and detects pollutants
- Destroys mold spores
- Monitors relative humidity
- Filters need to be replaced every 3 to 6 months
Primary active ingredient: N/A
Product type: N/A
Want to help prevent mold before it forms and kill existing mold? This air purifier destroys mold spores that come into contact with its built-in PECO-Filter. In independent laboratory tests, the filter was found to effectively remove 99.9% of airborne mold spores within two hours of operation. The brand offers a 30-day trial, so if you’re not happy with your purchase, you have the option to return it.
We love how compact this air purifier is and the fact that it’s actually aesthetically pleasing (way more so than most others on the market). The brand has a corresponding app, which you can use on your iPhone or iPad to control the purifier’s features. An energy-efficient choice, it’s incredibly quiet, too, at just 39 decibels on low speed.
While it can be tempting to reach for extra-strength mold killers or a bottle of bleach, these best natural mold killers are a much safer and healthier choice. The take-home, according to Tessier, is doing the best you can with the tools you have to help keep your home safe from mold. To help prevent the mold from growing in the first place, monitor your home environment and consider investing in a better air purifier.