Do Diffusers Cause Mold – And How To Prevent It

With aromatherapy gradually becoming mainstream, diffusers are now a common sight in American homes. Since diffusers are generally used for long hours, it is essential to know if they can cause the growth of microbes, like molds.  

Diffusers that use water (primarily ultrasonic and warm mist) can cause mold growths within the reservoir and outlet, and disperse the mold spores around the home. Mineral deposits from using tap (or hard water) can provide nutrition for mold. Some diffusers can also cause mold growths by affecting the relative humidity of the immediate space.

Moisture is a significant growth-promoting factor for mold. This article discusses various types of diffusers and whether or not they cause mold by increasing the humidity in the environment or by providing the ideal habitat inside the diffuser itself. We also dig into different essential oils and their impact on mold growth.  

What Is Mold?

Molds are moisture-loving, microscopic, multicellular organisms found across all ecosystems. In the air, they occur as mold spores, measuring as high as 50,000 counts per cubic meter.

In contrast, on surfaces like wood, wall, furniture, etc., spores usually sprout and form colonies that appear as black, gray, green, fuzzy, or powdery patches.  

Molds and Moisture

Mold spores can even exist in dry areas. However, adequate humidity, i.e., relative humidity greater than 55%, is required for the spores to sprout and form colonies.  

Therefore, maintaining indoor relative humidity at the EPA recommended ideal level, between 30 to 50%, is crucial to keep germs away. 

Types of Diffusers and how they work

There are four main types of diffusers, which is based on how they disperse essential oils. How they disperse oils influences whether they are prone to mold growths (or not).

Nebulizing Diffuser

Nebulizing diffusers pressurize the incoming air stream to break up essential oils. The oil is then distributed in the form of a fine mist. 

Ultrasonic Diffuser

These diffusers have a water tank to which you add a few drops of essential oils. A metallic disc vibrates at an ultrasonic frequency, propelling a water mist containing aromatic oil molecules into the room. 

Heat Essential Oil Diffuser

In heat diffusers, a heating element vaporizes oil molecules. Some models use a water-oil mixture instead of pure oil. 

Evaporative Oil Diffuser

These diffusers use scent pads fused with essential oils. Air circulating in the room evaporates the oil from the pad, spreading it through the surrounding area.  

Note that ultrasonic units and some models of heat essential oil systems also increase moisture levels in the immediate area.  

Can Diffusers Grow Mold?

When not cleaned regularly, all water-containing diffusers can become a favorable breeding ground for mold – here’s how: 

  • If diffusers that use water are not cleaned well, or the reservoir water is not changed frequently (at least every two days), they can grow mold, especially in the tank and outlet.
  • If hard water or unfiltered tap water is used, the minerals and impurities form clogs and scales, which provide nutrition for mold, facilitating their growth.  
  • If the diffuser is not allowed to dry after cleaning, it can contribute to mold growth. 

note: some nebulizing and evaporative diffusers are waterless and are less prone to mold.

This mold can then be dispersed into the air, making it unsafe to breathe. 

While some cleaning instructions can vary depending on the construction of the model, here is a general maintenance guide for diffusers to prevent mold growth: 

  1. Turn the diffuser off, and disconnect its power supply. 
  2. Use a clean cloth to remove the dust from the external part of the diffuser. 
  3. Drain the water tank, and then rinse it thoroughly. 
  4. Disinfect the tank by filling the diffuser halfway with a vinegar solution (1:1 white vinegar and water). Let it sit for 10 minutes.  
  5. Vinegar has acidic properties and can kill mold buildup. It can also remove clogs and scales.  
  6. Empty the tank again, and keep rinsing it till the vinegar smell is gone.  
  7. Finally, clean the mist vent with water and dish soap.  
  8. For evaporative diffusers, replace the scent pads frequently. 

Some oils can contain chemicals that may damage a diffuser’s material. Check your manual for the oil (or mixture of oils) suitable for the unit.  

Does Moisture From Ultrasonic Diffusers Cause Mold?

Ultrasonic diffusers humidify the air. While this can make the environment comfortable in dry areas, it can also be a serious problem in humid climates.  

Running an ultrasonic diffuser for 30 minutes can increase relative humidity levels by up to 24%. We know that moisture exceeding 55% relative humidity facilitates mold growth. Therefore, ultrasonic (or other moisture-increasing) diffusers are not a great choice for humid areas.  

However, using a dehumidifier to keep humidity levels in check can help resolve this issue. Alternatively, only using a diffuser for a few hours a day will prevent it from overly impacting on humidity levels.

How Do Essential Oils Impact Mold Growth?

Essential oils are known to relieve anxiety and stress and enhance mood. However, recent studies have shown that some oils actually have antimicrobial effects and can inhibit the growth of germs like mold, bacteria, and viruses.  

Essential oils are plant extracts and contain active chemicals like aldehydes, ketones, and phenols. These substances inhibit mold metabolism, denature their proteins, and disrupt cell membrane structure, thereby restricting mold growth

Clove oil is considered the most efficacious antifungal activity, whereas eucalyptus, lavender, tea tree, and citrus can also be used for mold control.

Plentiful Air has a complete guide to antibacterial and antifungal essential oils available here.

Best Essential Oil Diffusers

Here are some of the best essential oil diffusers you can consider investing to enjoy the aromas of your favorite oils: 

Homedics Aroma Diffuser

This Homedics Aroma Diffuser is an ultrasonic device. With a sleek shape and classic design, this unit can perfectly blend with all kinds of decor. 

It has a 130 ml reservoir that can run for 12 hours in a continuous mode. On the other hand, using this device intermittently can make it last for up to 12 hours. 

It has LED lights which can add to the aesthetic appeal of your room. An important upside of these lights is that they’re not very bright and can function as a night light. It can switch between various calming colors that promote relaxation. 

Pure Enrichment PureSpa Portable Car Diffuser

Pure Enrichment is a leading brand for domestic appliances. We recommend their PureSpa Portable Diffuser as a perfect fit for cars and small rooms. 

This is an ultrasonic diffuser that not only enhances the environment with fragrance but also humidifies and makes driving comfortable. It has a 50 ml water tank and can provide a fresh supply of essential oil mist for four hours.  

The device has a sleek design and easily fits into car cup holders. Being lightweight and portable, it can be carried around anywhere conveniently.  

The LED lights on this device illuminate in eight colors. Using the touch-controls, you can decide if you want to alternate between all the colors or would prefer having a solid light. 

The USB connectivity allows you to easily charge the device.  

All-in-all, PureSpa Portable Car Diffuser should be your go-to for small rooms.  

Pure Enrichment PureGlow Crystal 2-in-1 Salt Lamp And Diffuser

Next up, we have a combination device, PureGlow Crystal 2-in-1 Salt Lamp and Diffuser.  

A diffuser is an ultrasonic unit with a 160 ml tank that provides a long, 16-hour runtime. Other than the fragrance, you also get to benefit from the visual appeal and salt therapy of the original Himalayan salt lamp.  

The efficiency, natural ambiance, 5-year warranty, and excellent customer support have made this unit a popular customer choice.  

Frequently Asked Questions

What are the effects of mold?

Molds produce chemicals like mycotoxin that can lead to severe allergies, a weak immune system, DNA mutations, and even life-threatening malignancies.  

Here are some of the common airborne mold and their health implications: 

  • Aspergillus: allergic reactions in lungs and other vital organs 
  • Cladosporium: allergies, asthma, and eye infections 
  • Penicillium: DNA mutations and irreversible neurological and psychological damage 
  • Fusarium: impairs intestinal health and immune response 

Mold infections usually spread through inhalation of spores. They can trigger the respiratory system, resulting in shortness of breath and exacerbating asthma and emphysema.  

Eating contaminated food is another common way of acquiring infection or mucormycosis.  

Although the EPA has not given any healthy levels of mold spores, the Center for Disease Control and Prevention (CDC) says no amount of mold is safe in a residential area.   

Do Diffusers Cause Dampness?

Ultrasonic diffusers and some models of heat essential oil diffusers use water to work. These disperse water vapor into the room and can slightly increase the relative humidity of the immediate environment. 

Can Essential Oils Grow Mold?

Essential oils cannot grow mold. In fact, they have potent antifungal activity and can significantly reduce mold growth. However, old essential oil residue left in a diffuser can mix with dust and dirt to form a hardened deposit that provides nutrition for mold.

Theresa Orr

Theresa Orr holds a PhD in Earth Science and specializes in determining past climates from rocks using geochemistry. Her passion for clean water, soil and air drives her to provide easy to understand information for everyone to read.

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