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Why I Don’t Recommend Diffusing Oils

By Jodi Cohen

A tranquil setting with an essential oil diffuser releasing a delicate stream of vapor next to a blooming orchid and bottled essences, creating a serene and aromatic atmosphere.

I do not recommend diffusing essential oils.

By diffusing, I mean using a device to break essential oils down into smaller molecules, and disperse the essential oil particles into the air.

At best, I find diffusing to be wasteful and inefficient.  Direct Inhalation (holding a bottle of essential oil directly under your nose) is the most effective method of consuming essential oils followed by topical application.  At worst, it could be harmful.


7 Reasons Why I Don’t Recommend Diffusing Essential Oils

My biggest concerns about diffusing essential oils are:

1. It’s Less Efficient

Inhalation is the most efficient and effective method of consuming essential oils.  This means, you can inhale directly from the bottle – just hold the bottle directly under your nose and inhale 3 – 5 times.

Your sense of smell, which is part of your olfactory system, is one of the most powerful channels into the body.   In fact, research shows that inhalation can be the most direct and effective method for using essential oils. The entire process from the initial inhalation of an essential oil to a corresponding response in the body can happen in a matter of seconds.

This is one reason that anesthesia is delivered via inhalation and cocaine is most commonly snorted through the nose. The popularity of way drugs are used often depends on how quickly the administration channel allows the drug to reach the brain and how long it takes for effects to kick in. It is interesting to note that inhaling a substance is one of the more rapid ingestion routes since the drug bypasses the digestive tract and, later, the liver, where the drug would be subjected to digestive processing.

When drugs are inhaled, they go straight into the bloodstream via blood vessels in the nasal cavity.  Upon entering the bloodstream, the drugs travel quickly to the brain, thus eliciting a host of intense effects shortly after snorting.

Similarly, when inhaled through the nose, essential oils efficiently pass through the blood brain barrier in the area surrounding the olfactory nerve. A true blood-brain barrier is 8 cells in thickness. The number of cells which constitute the layer around the olfactory nerve is only 4 to 5 cells thick. Hence, it is very easy for the oils to pass straight through to the brain when breathed in through the nose.  Breathing in through the lungs, while also effective, is less efficient.

2. It’s Wasteful

Diffusion uses more oil more quickly.  Inhalation barely uses any oil and it goes directly and efficiently into the olfactory channel.  Topical application requires only a drop or two and it goes directly into the bloodstream.

Diffusion, on the other hand, usually requires 5 or more drops of oil which circulates in the air where it may or may not be absorbed into your body.

According to an article titled “Are you diffusing essential oils safely”, when you diffuse an essential oil, it’s estimated that only 50% of the oil molecules you’re diffusing actually make it into the body to be used in the following two ways. First, around 95% of essential oil molecules you breathe in are passed into the lungs where they cross over into the circulatory system and are metabolized into molecules the body can use via the liver.” Out of all the air in the room, you are only breathing in a small fraction. This means most of the oil you drop into your diffuser is probably going to waste.

Oils can be expensive and it feels wasteful to burn through them, quite literally. I have also noticed most people over-diffuse – running a diffuser all day long, which would be like popping an Advil every 5 minutes.  If you love diffusing oils, try to limit it to 20 minutes twice a day, not round the clock.

Essential oil safety expert Robert Tisserand advises that “Intermittent diffusion is much more effective, as well as being safer, than continuous diffusion.” Intermittent means take a break of at least an hour between diffusing.  He explains, “This is because our body, especially our nervous system, habituates after this length of time. With continuous diffusion, while benefits do not increase, there is evidence that the body becomes stressed in various ways.”

Tisserand also advises “very low levels of diffusion – so the essential oil is barely noticeable”.  Over diffusion, or blasting your diffuser all day, is akin to over-medicating.  It is not only wasteful, but it can be harmful, especially for your pets.

3. It Can Be Harmful for Pets (especially cats)

A toxin can be defined anything that we cannot easily neutralize and eliminate.  Different animals are more sensitive to different toxins.  For example, rat poison (cholecalciferol) is actually Vitamin D, which is “considered a safe dietary supplement for humans”, but not for rats.

Cats cannot detoxify essential oils.  The oils are rapidly absorbed both orally and across the skin, and are then metabolized in the liver. Cats lack essential enzymes in their liver (like glucuronyl transferase) which make it difficult to metabolize and eliminate essential oils. Cats are also very sensitive to phenols and phenolic compounds, which can be found in some essential oils like Oregano, Clove and Thyme which contain the phenol constituent’s carvacrol, eugenol and thymol.

Diffusing spreads oil through the house and potentially on surfaces where cats may spend time.  Topical inhalation or inhalation directly from the bottle significantly reduces the risk of harm to your cat.  Care should also be taken to avoid diffusing essential oils around fish, reptiles and birds.

4. It Can Be a Breeding Ground for Mold

I know that diffusing essential oils is often touted as the best natural solution for mold, but I do not believe they are a universal magic bullet.  In other words, while essential oils can be beneficial in treating minimal levels of mold on easy to clean surfaces, like countertops, glass or tile, they cannot be used to eliminate toxic mold on porous material, such as drywall, as they cannot permeate drywall.

I do not recommend using essential oils to eradicate large mold infested areas as mold spores can spread easily and there is too great a risk of spreading the very spores you are attempting to kill and making the problem worse.  This is one of the concerns over diffusing essential oils in mold infested environments, that you might actually be feeding the problem.

The other concern is that mold can grow in diffusers, especially plastic diffusers, and if you are not properly cleaning your device, the act of diffusing can spread toxic mold spores all over your home.

Some essential oil diffusers need to be filled with a mixture of water and essential oils – the very raw materials (moisture and food) that mold requires to flourish.

To avoid mold build-up, always clean your diffuser between uses.  Vinegar, citric acid, or rubbing alcohol can be used to clean the device and removing any oil residue.  For example, you can run the diffuser for 5 minutes with a mixture of clean water and 10 drops of vinegar, then rinse clean.

5. Heat and Plastic Don’t Mix

Many low cost diffusers are made of plastic and use heat to help diffuse the oil particles.

Just as you want to avoid storing hot food in plastic containers or heating food in plastic as the heat amplifies the leaching of toxic chemicals like BPA into food and liquid.

For example, plastic containers leach up to three times more bisphenol A (BPA), a chemical found in polycarbonate plastic containers; into foods and liquids when heated, according to a 2009 study published in the “Journal of Toxicology and Environmental Health.”  High-fat materials, like fat soluble essential oils absorb more BPA than other substances.

Research has demonstrated that BPA particles can be inhaled and accumulate over time.  “BPA is metabolized in the liver and is excreted with urine. Due to its phenolic structure BPA, has been shown to interact with estrogen receptors and to act as agonist or antagonist via estrogen receptor (ER) dependent signaling pathways. Therefore, BPA has been shown to play a role in the pathogenesis of several endocrine disorders including female and male infertility, precocious puberty, hormone dependent tumors such as breast and prostate cancer and several metabolic disorders including polycystic ovary syndrome (PCOS).”

Essential oils can also have a harmful effect on plastic, contributing to corrosion and deterioration of the plastic over time. If your plastic diffuser deteriorates, it can begin to emit harmful plastic particles into the air.  Heating essential oils also decreases their effectiveness. Essential oils are also flammable and heat could be an unnecessary danger.

6. Diffusion is Not Effective for All Ailments

Research indicates that the method of using essential oils should be adjusted depending on the chemical compounds that are expected to function.  For example, “lavender essential oil should be applied topically when the goal is to enhance wound healing. It is necessary to use the delivery method that is most effective to reach the clinical goals with the knowledge on how specific chemical compounds produce the effect.”

To this point, some essential oils can have harmful effects when diffused.  For example, the study notes that “when human subjects were exposed to lavender aroma through a diffuser, their working memory decreased and reaction time was slower in tasks that required memory and attention.”  In other words, diffusing lavender had a negative effect on cognition.

Other essential oils may be contra indicated for other conditions, like asthma, ADD or seizures.  For example,  essential oils containing constituents like aldehydes and phenols can irritate the mucous membranes, therefore, they should be not be diffused if asthma is an issue. Essential oils with high amounts of camphor, including sage, basil, rosemary and lavender can be dangerous to those with a propensity for seizures.  Finally, lavender can trigger a manic type reaction, instead of a sedative one, in those suffering from ADD/ADHD, according to an article in Atlantic Institute of Aromatherapy.

7. Sensory Tolerance

Just as you might develop a tolerance to a pain medication, requiring more of a drug over time to achieve the same level of relief, you can build up a tolerance to essential oils if you diffuse around the clock..

There is research that demonstrates that your senses are constantly adapting to new levels of stimulus and adjusting to that new baseline. You may even stop noticing the stimulus unless it changes again. This is what happens when you go “nose blind” to a smell. With a room diffuser, essential oil particles are released at a constant level for an extended period of time. Your body adjusts fairly quickly; your olfactory receptors essentially go “blind” to the essential oil molecules. This might diminish the benefit you receive from diffusing.


What Do I Recommend?

Direct Inhalation – Inhalation is the most efficient and effective method of consuming essential oils.  This means, you can inhale directly from the bottle – just hold the bottle directly under your nose and inhale 3 – 5 times.

Topical Application – Topical, or transdermal, application allows active ingredients of healing substances to be delivered across the skin. The combination of your skin’s permeability to fat-soluble substances and the small size of essential oil molecules make topical application ideal for balancing certain organ systems or stimulating various regions of the brain.  I detail how to apply to the body, the brain, for emotions, and to support symptoms in specific locations.  You can always apply on the bottom of the feet as well.

Dilution – If you do choose to diffuse essential oils, try to limit diffusion to 20 minutes no more than 2 times daily.  My favorite blend to diffuse that several practitioners use in their offices is Histamine Balance, which helps to clean the air and modulate the immune system.


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About The Author

Jodi Cohen

Jodi Sternoff Cohen is the founder of Vibrant Blue Oils. An author, speaker, nutritional therapist, and a leading international authority on essential oils, Jodi has helped over 50,000 individuals support their health with essential oils.