When you have a large stockpile of essential oils, sometimes you don’t use them as fast as you expected. This inevitably leads to finding a dusty lavender, peppermint, or frankincense and the question of whether the oils can still be used. The answer to this question seems obvious—essential oils are not immune to the laws of nature so they must “expire.” However, the true answer to this question is a bit more complex.
When we say shelf life and expiration, we are referring to whether an essential oil maintains its efficacy and safety over the course of time. Due to the unique nature of essential oils, they can retain their benefits and preferred composition for long periods, but it depends on the oil and the way that it is stored.
We know that oxygen, heat, and light (UV rays) can degrade the therapeutic value and composition of essential oils. When it comes to heat, chemical reactions accelerate with increasing temperature, doubling after 10 degrees C (50 degrees F). This means that essential oils can undergo chemical reactions if they are exposed to high temperatures.
Similarly, ultraviolet (UV) light influences chemical reactions. UV light splits molecules apart by breaking bonds between atoms. This creates a highly reactive atom that collides with another oxygen molecule to create ozone. Ozone is very unstable and so the UV light is able to quickly repeat this process. Italian researchers reported that exposing lavender essential oil to UV light significantly deteriorated its composition and biochemical profile. The bottom line: UV light can damage essential oils.
When a bottle is opened and drops of essential oil dispensed, oxygen enters the bottle and fills the new empty space (headspace). The more oxygen that enters the bottle the greater the potential for oxidation to occur. Oxidation is a chemical reaction that alters the chemical components of an oil, breaking them down into new constituents.
Published literature shows that essential oils like lavender, rosemary, pine, and cumin change when exposed to light or heat. They increase peroxide levels and their chemical composition was altered even at 100 degrees F. Some oils like pine may even change at room temperature. How much they change depends on the headspace in the bottle, actual ambient temperature, and exposure to direct sunlight.
There really is no blanket guideline when it comes to the stability of essential oils, nor a consensus about the exact conditions that may cause degradation because it will vary depending on the oil. For example, phenol-rich oils like thyme and oregano resist degradation because phenols are good antioxidants. Heavier weight sesquiterpene molecules are also more stable and resist chemical alterations better than lighter weight monoterpenes. Citrus oils that are predominantly the monoterpene limonene tend to easily change their composition during storage, especially if they have been opened.
In general, these storage guidelines should be followed:
- Store essential oils in dark glass
- Keep essential oils in a cool, dark place
- Store them away from heat sources and direct sunlight exposure
- Transfer opened essential oils into smaller bottles when you have used near 50% of the bottle
- If essential oils become heated (e.g. a hot car), allow them to return to room temperature before opening
- Consider storing citrus essential oils in a refrigerator—bring them to room temperature before use
The chemistry of an essential oil plays a significant role in how prone it will be to changing composition over time. Certain essential oil constituents are more prone to alteration than others.
Understanding that many variables contribute to the shelf life of an essential oil, and assuming proper storage has been maintained, the following can be used as a guide for essential oil shelf life:
| Constituent Family | Shelf Life Unopened | Shelf Life Opened | Essential Oil Examples |
| Monoterpene | 1–3 years | 1–2 years | Grapefruit, Lemon, Lime, Mandarin, Orange, Tangerine, Yuzu |
| Monoterpene + Monoterpenol | 1–3 years | 1–2 years | Palo Santo |
| Aldehyde + Ester | 4–7 years | 2–3 years | Cassia, Cinnamon Bark |
| Aldehyde + Monoterpene/Alkene | 4–7 years | 2–3 years | Lemon Verbena |
| Aldehyde + Monoterpenol/Sesquiterpenol | 4–7 years | 2–3 years | Lemon Eucalyptus, Lemon Myrtle, Lemongrass, May Chang (Litsea), Melissa |
| Monoterpene + Ester | 4–7 years | 2–3 years | Balsam Fir, Blue Spruce, Douglas Fir, Siberian Fir, Silver Fir, Spruce (Black) |
| Ester | 4–7 years | 2–3 years | Arborvitae (Western Red Cedar), Roman Chamomile, Wintergreen |
| Ester + Alkene/Ketone/Monoterpene | 4–7 years | 2–3 years | Helichrysum |
| Ester + Monoterpenol | 4–7 years | 2–3 years | Clary Sage, Jasmine Absolute |
| Ester + Oxide | 4–7 years | 2–3 years | Cardamom |
| Ether + Monoterpene/Ketone | 4–7 years | 2–3 years | Fennel, Star Anise |
| Ketone + Monoterpenes | 4–7 years | 2–3 years | Camphor, Dill, Sage CT alpha-thujone, Spanish Sage, Spearmint |
| Ketone + Sesquiterpene/Ether/Alkene | 4–7 years | 2–3 years | Davana, Manuka, Turmeric |
| Monoterpene + Alkene/Sesquiterpene | 4–7 years | 2–3 years | Celery Seed, Cypress, Frankincense, Juniper Berry, Pine (Scotch/ Scots), Pink Pepper |
| Monoterpene + Alkene/Phenylpropanoid | 4–7 years | 2–3 years | Ravensara |
| Monoterpene + Ether | 4–7 years | 2–3 years | Nutmeg |
| Monoterpene + Sesquiterpene/ Sesquiterpenol | 4–7 years | 2–3 years | Elemi, Kunzea, Yarrow |
| Monoterpenol | 4–7 years | 2–3 years | Ho Wood, Rosewood |
| Monoterpenol + Aldehyde/Monoterpene | 4–7 years | 2–3 years | Cilantro, Citronella, Magnolia, Marjoram |
| Monoterpenol + Ester/Monoterpene | 4–7 years | 2–3 years | Bergamot, Coriander Seed, Geranium, Lavandin, Lavender, Neroli, Palmarosa, Petitgrain, Rose, Spike Lavender, Tea Tree (Melaleuca) |
| Monoterpenol + Ketone | 4–7 years | 2–3 years | Cornmint, Peppermint |
| Monoterpenol + Phenylpropanoid/Oxide | 4–7 years | 2–3 years | Basil (Sweet) |
| Monoterpenol + Oxide | 4–7 years | 2–3 years | Rosalina |
| Oxide + Monoterpene/Monoterpenol/ Alkene | 4–7 years | 2–3 years | Bay Laurel (Laurel Leaf), Eucalyptus, Cajeput, Fragonia, Myrtle, Niaouli |
| Oxide + Ketone/Monoterpene/Alkene | 4–7 years | 2–3 years | Rosemary, Sage CT 1,8-cineole |
| Phenol + Monoterpene/Sesquiterpene | 4–7 years | 2–3 years | Ajowan, Oregano, Thyme |
| Phenylpropanoid + Monoterpenol | 4–7 years | 2–3 years | Basil (Tropical) |
| Phenylpropanoid + Sesquiterpene/ Monoterpene | 4–7 years | 2–3 years | Allspice, Cinnamon Leaf, Clove Bud |
| Sesquiterpene + Alkene/Ester/Monoterpene | 4–7 years | 2–3 years | Black Pepper, Ylang Ylang |
| Sesquiterpene + Oxide | 4–7 years | 2–3 years | German Chamomile |
| Sesquiterpene/Sesquiterpenol | 7–12 years | 5–10 years | Atlas Cedarwood, Blue Tansy, Copaiba, Ginger, Himalayan Cedarwood, Patchouli, Sandalwood (Australian, Hawaiian, Indian, New Caledonian), Spikenard, Texas Cedarwood, Virginia Cedarwood, Vetiver |
| Sesquiterpene Ether + Sesquiterpene | 7–12 years | 5–10 years | Myrrh |
| Sesquiterpene Ketone | 7–12 years | 5–10 years | Buddha Wood |
| Sesquiterpenol + Alkene/Sesquiterpene | 7–12 years | 5–10 years | Amyris, Carrot Seed, Blue Cypress |
With proper storage (cool, dark place away from heat sources), essential oils have a long shelf-life. Indeed, researchers found that peppermint oil properly stored for about 50 years—stored in a cool dark place in dark glass and sealed with wax—met or exceeded the quality and antimicrobial activity of a fresh sample. This demonstrates that oils can maintain their quality and safety for years.
Unfortunately, most consumers will not be able to perform a chemical analysis of the essential oil to determine if the composition of a stored oil has changed. Instead, consumers must rely on their senses. A good indication of an altered essential oil is its aroma. If the oil smells differently, this is an indication that the chemical composition has changed. Citrus oils may have white chunks floating in them as they go bad. Those essential oils that are labeled for consumption may have an altered taste. Lastly, altered essential oils may cause greater skin irritation.
So, the answer to the question from the beginning is—it depends? It depends on the oil and its composition as well as storage conditions.
REFERENCES:
Gismondi A, Canuti L, Grispo M, et al. Biochemical composition and antioxidant properties of Lavandula angustifolia Miller essential oil are shielded by propolis against UV radiations. Photochem Photobiol. May-Jun 2014;90(3):702-8.
Turek C, Stintzing FC. Impact of different storage conditions on the quality of selected essential oils. Food Res Int. 2012 Apr;46(1):341-53.
Mehdizadeh L, Pirbalouti AG, Maghaddam M. Storage stability of essential oil of cumin (Cuminum Cyminum L.) as a function of temperature. Int J Food Prop. 2017; 20(Sup2):1742-50.
Gochev V, Stoyanova A, Girova T, et al. Chemical composition and antimicrobial activity of Bulgarian peppermint oils. Sci Papers. 2008;36(5):83-89.
