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.
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 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.
In essence, pure distilled essential oils are fine when exposed to heat 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?
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