One of the most frequently asked questions I get regarding essential oils is how hot and cold temperatures affect their usefulness and integrity. Does exposure to temperature extremes make them lose their potency? Does it change the chemical makeup of the oils? Should you throw away your oils if they have been exposed to high temperatures?
Today I want to answer these questions and a few more!
How Hot and Cold Temperatures Affect Essential Oils
It goes without saying that essential oils do best when stored tightly sealed in a cool dark place in order to preserve their therapeutic properties. Stored in this way, pure essential oils can last for years and retain practically all of their original chemical components and potency.
But what happens if these precious oils are exposed to heat or cold?
It’s a common misconception that if an essential oil is exposed to heat, it will automatically lose its medicinal qualities.
This isn’t necessarily true.
How Hot and Cold Temperatures Affect Essential Oils
If a pure essential oil is temporarily exposed to heat like if you forgot it in a hot car that reached upwards of 140 degrees, the oil would still be good as new as long as it stayed sealed until cool.
I think it’s easy to forget that these amazing oils come from extraction processes (aka distillation) that use temperatures between 240 and 260 degrees (115-125C), WELL over the boiling point of water.
So, by nature, essential oils are born from high temperatures and will remain stable (as long as they are capped tightly closed) even if left in a hot car.
Having said this, you still need to be aware that there are three main groups of essential oils – distilled, expressed, and chemically extracted.
The ones that are not affected by heat when capped tightly closed are distilled essential oils. I’ll briefly go over the other two types later.
Another thing to note is carrier oils. These are often used as the base for roll-on recipes, lotions, balms, salves, etc.
These types of oils are typically cold-pressed from the nuts or seeds of a plant to produce the oil. Oils made in this way include sweet almond oil, grape seed oil, coconut oil, etc.
It is important to note that carrier oils are susceptible to the ill effects of heat exposure no matter how much distilled essential oils are added to them. A rancid carrier oil will still turn rancid!
The Flash Points of Essential Oils
A flash point is a point at which an essential oil is heated one degree at a time until a temperature is reached where there is a flash of fire when a tiny wand of flame hovers over the surface. This is what determines the vaporization of the most volatile compounds found in that particular oil.
Many essential oils have pretty high flash points, however, there are, of course, essential oils that have lower flash points, some even as low as 100 degrees.
When essential oils have low enough flash points that even the temperature inside a hot car can cause them to vaporize, that’s when keeping your essential oils tightly sealed really comes in handy.
Even though the components within the essential oil may temporarily separate within the bottle, once the essential oil cools down again, these components re-condense and become “whole” again, leaving their chemical makeup intact.
So, the rule of thumb here is to refrain from opening your oils until they have cooled.
Below is a list of essential oils (distilled, expressed, and chemically extracted) and their flash points. Just keep in mind that citrus essential oils and absolutes are more likely to break down when exposed to their flash point or higher no matter how tightly closed their caps may be.
Here are some of the most common essential oils and their flash points:
• Allspice – 199F / 93C
• Amyris – 287F / 142C
• Aniseed - 194F / 90C
• Basil - 176F / 80C
• Bay Leaf - 140F / 60C
• Benzoin – 338F / 170C
• Bergamot - 136F / 58C
• Black Pepper - 129 F / 54 C
• Cajeput - 126F / 52C
• Camphor – 113F / 45C
• Caraway – 133F / 56C
• Cardamom – 134F / 56C
• Carrot Seed – 120F / 49C
• Cassia – 188F / 87C
• Cedarwood (atlas) - >212F / >100C
• Chamomile (German) - 140 F / 60 C
• Chamomile (Roman) - 135F / 57C
• Cinnamon Leaf - 194F / 90 C
• Citronella - 135F / 57C
• Clary Sage - 174F / 79 C
• Clove Bud - >212 / >100C
• Clove Leaf – 200F / 95C
• Coriander Seed – 145F / 63C
• Cypress – 108F / 42C
• Dill – 118F / 48C
• Elemi – 129F / 54C
• Eucalyptus citriodora – 125F / 52C
• Eucalyptus globulus – 130F / 54C
• Eucalyptus radiata - 117F / 47C
• Fennel (sweet) – 144F / 62C
• Frankincense – 124F / 51C
• Galbanum – 140F / 60C
• Geranium - 176F / 80 C
• Ginger - 135F / 57C
• Grapefruit (pink) – 113F / 45C
• Grapefruit (white) - 109F / 43C
• Helichrysum – 124F / 51C
• Ho Wood – 168F / 76C
• Hyssop – 125F / 52C
• Labdanum (aka cistus)– 188F / 87C
• Lavender - 162F / 72C
• Lavender (40/42) - 160F / 71C
• Lavender (spike) – 128F / 53C
• Lemon – 118F / 48C
• Lemongrass - 169F / 76C
• Lime – 114F / 46C
• Jasmine (absolute) – 200F / 93C
• Juniper berry – 106F / 41C
• Mandarin – 107F / 42C
• Marjoram – 125F / 52C
• Manuka – 138F / 59C
• May Chang – 136F / 58C
• Melissa – 167F / 75C
• Myrrh – 199F / 93C
• Myrtle – 113F / 45C
• Neroli – 153F / 67C
• Niaouli – 127F / 53
• Nutmeg – 100F / 38C
• Orange (blood) – 116F / 47C
• Orange (sweet) – 109F / 43C
• Oregano – 131F / 55F
• Palmorosa - 199F / 93C
• Patchoul - >212F / >100C
• Peppermint - 151F / 51C
• Petitgrain - 151F / 66C
• Pine – 149F / 65C
• Ravensara – 134F / 57C
• Rose (absolute) – 150F / 65C
• Rosemary - 105F / 40C
• Rosewood – 183F / 84C
• Sage – 129F / 54C
• Sandalwood – 199F / 93C
• Spearmint - 151F / 66C
• Spikenard – 160F / 71C
• Tagetes – 77F / 25C
• Tangerine - 124F / 51C
• Tea Tree - 135-142F/ 57-61C
• Thyme – 129F / 54C
• Vetiver - >212F / >100
• Wintergreen – 200F / 93C
• Yarrow – 121F / 50C
• Ylang Ylang - 189F / 88C
Why bother knowing the flash points of essential oils?
Because it’s handy to know when adding essential oils to hot liquids like wax, carrier oil, and other bases when making lotions, salves, candles, etc.
So, while a true essential oil will be fine if exposed to heat while tightly sealed, if you add the essential oils too soon to a recipe while the base ingredients are too hot, the essential oils will evaporate and you risk losing its therapeutic benefits.
Expressed Essential Oils
Expressed essential oils, like all cold-pressed citrus essential oils, are incredibly delicate even at temperatures as low as 100 degrees (38C) which is why they do best stored in the fridge.
This is the only time cold storage makes an impact on the integrity of an essential oil since storing distilled or chemically extracted essential oils in the fridge doesn’t negatively or positively influence the oil.
Expressed essential oils include bergamot, lemon, lime, grapefruit, orange, mandarin, tangerine, etc.
Absolutes
Absolutes are chemically extracted because their therapeutic benefits are destroyed by heat. These oils include jasmine, neroli, rose, and onycha to name a few.
These oils can be damaged in temperatures in excess of 90 degrees (32C) and need to be stored in a cool dark place lest their delicate aromas are unfavorably altered.
This is because absolutes (just like expressed essential oils) contain large molecules that cannot make it through distillation so other methods must be used to extract the essential oil.
These larger molecules are more likely to break down into smaller, unpleasant smelling molecules when exposed to heat.
It is best to keep these precious and often expensive essential oils in the fridge.
What About Cold Temperatures?
If tightly sealed, cold temperatures will not harm or affect the potency of essential oils, even if they freeze solid.
Allow the essential oil to thaw completely before use.
In Conclusion
In essence, pure distilled essential oils are fine when exposed to heat and cold if tightly sealed or when below their flash point when used in recipes.
Absolutes and expressed essential oils need to be more carefully cared for and do well when kept in cold dark places, even in the fridge! This includes any essential oils blends that are in a base of carrier oil to help protect the therapeutic qualities of the essential oils.
Have you ever had your essential oils exposed to hot or cold temperatures? How did they fare?
You may also enjoy reading:
Citrus Essential Oils – Essential Oils 101
What You Need to Know About Phototoxic Essential Oils
Beginners Guide to Essential Oils- Part 1
The Best Essential Oils for Your Skin Type
Shannon says
Hello, Tash,
Thank you for your informative article. I learned about how heat can affect EOs, but did not see mention of cold.
I discovered a pouch of my EOs that had fallen down by the spare tire in my car. It’s been there for three years, in sub-freezing winters and hot summers. They are doTERRA Lavender, Serenity, Peppermint Touch, Peace Touch, Thinker Roll-on, and Adaptiv Roll-on.
Have the roll-ons probably lost their healing properties because of the carrier oils?
And how about the below-freezing temperatures? (I live in Tennessee.)
Thanks for your help!
Shannon
Tash says
Hi there! If the bottles have been sealed really well, they might be okay! However, if they contain carrier oils, those oils might have gone rancid. You would have to give them a smell to see if you detect any "crayon" odor.
Isabel says
Can it still be used on skin?
thomas Sheridan says
I would like to know if it is okay to still use essential oils that have been exposed to hot weather? I know the potency will be reduced , 2 drops instead of 1 drop, for example
Leandra says
Hi Tash. Have really enjoyed reading your questions/answers. I am also very interested in using Essential Oils in my candles instead of synthetic fragrance. I'm happy to do lots of testing but what sort of wax to EO ratio do you recommend? eg. If I had 600 grams of wax melted, how many drops of oil would you recommend? (I'm sure this would change according to the fragrance but a rough idea would help me get started on my testing process). Thanks so much.
Josh says
When you talk about flash points are talking about the tempurature at which the oil ignites and catches fire? Whenever I've heard the term flash point referred to oil it is the ignition point. Can you better define what you mean by "flash point" in this article?
Katelyn Roy says
Hi, I'm a junior in High School and I'm conducted my own experiment of which solvent works better for oil paint, Gamsol (Gamblin product) or Rosemary Essential Oil. I thought I'd share my write up when it's complete because I'm using your expertise on Essential Oils to support my hypothesis and conclusion. Also, Rosemary Essential Oil was better.
Ewa says
Dear Tash, I've come across your awesome blog while searching the info about how to deal with Athleete's Foot (AF). Maybe you know the answer to some of these questions:
1) We used home ways to fight AF, they didn't help. Clotrimazolum helped (me and my kids, 4 and 6 years old). Now, I I'm trying to find info how to prevent recurrence, so how to effectively desinfect socks, shoes, furniture, floors, etc. from fungi SPORES, because I understand that even if we managed to get rid of the symptoms, there are SPORES that are very resistant to many factors (heat, chemicals, etc.) thanks to which AF can to recur. Do you know if any essential oil helps to fight the SPORES? For example tea tree oil?
2) What essential oil can we use preventively on our feet and how (what proportion with carrier oil, how often to apply, etc?). My kids are almost 4 and 6 years old.
2) How can I effectively desinfect shoes and socks from fungi AND SPORES?
3) Do you know if washing socks and clothes in the washing machine in 95° Celcius (I'm from Poland) kills fungi AND SPORES? I use home made washing powder and wanted to add tea tree oil to the washing but from your blog I just learned that the flash point of tea tree is 135-142F/ 57-61C, so for washing in 95C it's useless. Maybe it's more effective to wash in 40C but with addition of tea tree oil (how many drops per washing?)
Greetings,
Ewa
Tash says
Hi, Ewa!
So, for the washing, you will actually want to use bleach to launder the socks if possible. It will definitely kill the spores associated with athlete's foot and is not affected by heat like essential oils.
For topical treatment on the feet, you can mix 6 drops of tea tree essential oil per 1 oz (30ml) of carrier oil (coconut oil is good as it is already anti-fungal) for the children and 12 drops per 1 oz for yourself. Apply daily 1-2 months AFTER symptoms disappear.
Using essential oils in the washing machine won't do much since they won't mix with water. You will have much better luck using bleach. I normally don't like using bleach, but for something like this, it really is one of the best ways to get rid of the spores.
For shoes, you can add 12 drops of tea tree essential oil per 1 oz of water and spray the shoes inside and out 1-2 times daily to help kill the spores. You can also use this spray on bedsheets and other surfaces.
Best of luck!
lrng4life says
My husband have struggled with Athlete's Foot (also known as a yeast infection) for years. . . We have discovered that vinegar baths works well. When an infection is active we do 2 vinegar baths a day with about 1.5 - 2 cups of of vinegar added to a luke warm tub of water. We also take a probiotic and eat a low sugar yogurt (as sugar feeds the yeast infection). Our most current discovery includes using coconut butter on the infected skin. This fights the yeast and stops the itching. We also use vinegar as a fabric softener in our laundry as this kills any spores living in our clothes.
Xin says
Hi Tash,
I am interested to make my own candles with essential oils but I am concerned that the qualities of the essential oils might be compromised in the process of adding them into the wax as well as during candle burning. What are your thoughts on this? Thanks so much!
Tash says
yeah, I actually use essential oils I'm not tooooo worried about. I still use high quality, but not my fanciest or most expensive oils. The oils I use most often for candle making are from Whole Foods (their 365 brand) and it works out well. Burning essential oils in a candle is definitely not the best way to get their therapeutic benefits, only the smell. If you want the healing benefits from candles, I recommend diffusing them or using them topically. 🙂
Mona says
Hello! I too would like to try making soy candles with EO mainly to avoid the chemicals of synthetic fragrances and not specifically for the aromatherapy. I have read some EO actually become dangerous when burned and inhaled, as well as having less scent and costing more. Which EO's do you feel are safe when creating a scented candle, for both humans and pets in the house. Thanks!
Cubo says
Thank you for this post. It kind of answered a question that I have been searching for but I sure would like a clear answer --> Do the LED lights found in some nebulizers really damage the properties of EOs when the lights are turned on?
One company that makes nebulizers say they don't put lights in their nebulizers because of this fact as well as the chance that people will accidentally drip EOs into the air channel that leads to the electronics (in the base) that run the lights and thereby causing it to break.
I cannot imagine that a little LED could cause so much heat but I know very little about EOs.
Thanks for responding. Feel free to reply in this post or to my email address.
Miatta Karneh says
Hi Tash
Thanks for this blog page, it's great.
A quick question. I'm making some hair oil spray with a touch of essential oils. Is this safe on the scalp and hair and do I need to get it approved before selling??
sandeep says
Just a note on temperature, I left my diffuser in the car all day after buying it. I live in Alberta and it was about -10 here today. It took about an hour of warming up in the house before any fog came out. I was ready to send it back. My husband convinced me to let it warm up and I am glad he did.
Louise says
Hi Tash! Absolutely love your blog and come here often to read up on EO's. Have a quick question I can't seem to find an answer for. I've been making my own face creams and lotions etc using essential oils and after reading this blog on the flash points of essential oils have been extra careful to reduce the temperature of the carrier oil mixture before adding my EO's - generally at least a degree or so lower than the flash point of the EO I'm using. However, I'm just wondering if adding the EO's into a hot oil mixture is actually destroying their therapeutic properties and if I should be concerned? I read elsewhere someone said to get the temp down to 23C (73F) however a lot of my creams already start to set at that temp. (Sorry for long post!) Any ideas on where I could get some good info on this? Many thanks! :Louise
Tash says
Hi Louise!
I have grappled with this issue myself and have sort of given in on the projects that start to solidify beyond the point where you're able to mix in the oils. So, for the recipes I make that create more solid end products like lip balms, salves, soap, etc., I just try to wait as long as I can before adding them. For softer end products that are close to a petroleum, cream, or lotion consistency, I will add the essential oils after the product has cooled because it's still really easy to mix them in. I think you still get some of the benefits of the oils, but you're right, some of the therapeutic qualities will evaporate no matter what you do when adding them to recipes that harden up. I haven't found anything on how to avoid that, unfortunately 🙁
Louise says
Thanks Tash, really appreciate your reply. Glad I'm not the only one scratching my head over this one!