Essential oils are concentrated plant extracts that keep the natural smell and flavor of the plant they come from. This guide covers what they are, how they are made, what they are used for and what the National Institutes of Health sources say about risks.
We sell an assorted essential oil collection, so read this with that in mind. Where our own listing says more than the sources do, this page says so. For how-to detail, see our guides to using essential oils, using a diffuser and carrier oils.
The National Institute of Environmental Health Sciences defines essential oils as concentrated plant extracts, obtained by mechanical pressing or distillation, that retain the natural smell and flavor of their source.
Every essential oil has its own mix of chemicals, and that mix can vary even within one plant species, so two bottles with the same name may not be identical.
The NIH says essential oils are most often inhaled or applied diluted to the skin. Evidence for benefits is mixed, and swallowing large amounts is not recommended by the National Cancer Institute.
NIEHS notes that synthetic oils are not considered true essential oils, which is the main difference between an essential oil and a fragrance oil.
What Are Essential Oils?
Essential oils are concentrated plant extracts that retain the natural smell and flavor of their source. That is the definition from the National Institute of Environmental Health Sciences (NIEHS), part of the NIH.
- Plant-derived: They come from plants, so the scent of a lavender oil or an orange oil traces back to that plant.
- Concentrated: NIEHS describes them as concentrated, which is why they are used by the drop and not by the spoonful.
- Not synthetic: NIEHS says synthetic oils are not considered true essential oils.
How Are Essential Oils Made?
They are obtained through mechanical pressing or distillation, according to NIEHS. Pressing is how citrus peel oils are commonly made; distillation uses steam or heat to carry the scent compounds out of plant material.
- What NIEHS says: Essential oils are obtained through mechanical pressing or distillation. We found no figure on how much plant it takes per bottle in the sources we read, so we do not give one.
- Every oil is different: NIEHS says each essential oil has a unique composition of chemicals, and that this affects the smell, absorption and effects on the body.
- Batches vary: NIEHS adds that the chemical makeup can vary within the same plant species, or from plant to plant.
What Are Essential Oils Made Of?
Hundreds of chemical compounds, in a mix that is different for every plant. NIEHS says lavender oil and tea tree oil are each composed of hundreds of chemicals.
- Shared compounds: An analysis of 93 essential oils, cited by NIEHS, found limonene in 90 of them, alpha-terpineol in 87, linalool in 82 and eucalyptol in 79.
- Why NIEHS cites it: The eight compounds NIEHS tested in lavender and tea tree oil also turn up in most other oils, so the findings are not limited to those two.
What Are Essential Oils Used For?
Mostly for scent, through a diffuser or a few drops on a tissue, and sometimes diluted into a carrier oil for massage. The NIH says essential oils are most often used by inhaling them or by applying a diluted form to the skin.
- Inhaled: The National Cancer Institute lists room diffusers and drops on a tissue or cotton as indirect inhalation, and an inhaler made by floating drops on hot water as direct inhalation.
- On the skin: The NCI lists massage with oils diluted into a carrier oil, plus bath salts and lotions. Our carrier oil guide covers what to dilute with.
- How-to: Step-by-step methods are in our guide to using essential oils.
Do Essential Oils Actually Work?
The evidence is mixed. The National Cancer Institute says aromatherapy studies have shown mixed results, with some reports of better mood, anxiety, sleep, nausea and pain, and others showing no change.
- A large trial, no difference: In a 313-patient trial cited by the NCI, inhaled lavender, bergamot or cedarwood showed no difference in depression or anxiety between the groups.
- Sleep: The NIH says aromatherapy is sometimes used for insomnia but we do not know whether it helps, because little rigorous research has been done. Our sleep guide goes through the trials.
- What we do not claim: That any oil improves sleep, mood or stress. The sources above do not support that for a specific product.
Featured in this guide
Assorted Essential Oil Collection
10 ml single-botanical essential oils in 19 scents. Full details are on the product page.
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Skin irritation, allergic reaction and sun sensitivity are the ones named for skin use, and swallowing them is not recommended. The NCI says allergic reactions and irritation can occur with long skin contact, and that swallowing large amounts is not recommended.
- Sun sensitivity: The NCI says sun sensitivity may occur when citrus or other oils are applied to the skin before going out in the sun.
- Hormone-like activity: NIEHS says lavender and tea tree oil, and some of their components, showed hormonal activity in test-tube studies and could affect the endocrine system. As dilution increased, that activity decreased.
- Reports in boys: NIEHS cites clinical research on a possible link between topical use of essential oils and breast tissue growth in prepubescent boys. The cases described skin use, not aromatherapy, and NIEHS says further studies are needed on inhalation.
- Their conclusion: NIEHS says using essential oils is up to the individual, and wants people to know about the findings.
How Are Essential Oils Different From Fragrance Oils?
An essential oil comes from a plant; a fragrance oil is made to smell like something and can be synthetic. NIEHS says synthetic oils are not considered true essential oils.
- Read the label: A true essential oil is named for its plant. A bottle called a fragrance oil, or a scent such as Sweet Pea or Cotton Candy, is a different product.
- We sell both: Our fragrance oils are for scenting candles and soaps. Our essential oils are single-botanical oils, which is what the collection below holds.
- Do not swap them: A fragrance oil is not an essential oil, so claims made about essential oils in the sources above do not carry over to it.
What Is in Our Assorted Essential Oil Collection?
The Assorted Essential Oil Collection is a set of 10 ml single-botanical oils, with 19 scents listed. The listing says each bottle holds one plant's oil with no carrier or fillers.
- What it is for: Diffusing, and skin use only after dilution, according to the product page. The listing says the oils are not to be ingested.
- Storage: The listing says to keep bottles sealed in a cool, dark place away from heat. We found no source for the storage times it gives.
When Should You Talk to a Health Care Provider First?
Before use if you take medicines, are pregnant or breastfeeding, have a medical condition, or plan to use oils around a baby. The NIH says to discuss decisions about treatment or care with your provider.
Essential oils are not a substitute for medical care. This guide is information, not medical advice.
Frequently Asked Questions
What are essential oils?
Concentrated plant extracts that retain the natural smell and flavor of their source, obtained by mechanical pressing or distillation, according to NIEHS.
Are essential oils the same as fragrance oils?
No. NIEHS says synthetic oils are not considered true essential oils. A true essential oil is named for its plant.
How do you use essential oils?
The NIH says they are most often inhaled or applied diluted to the skin. The NCI says swallowing large amounts is not recommended.
Do essential oils work?
The evidence is mixed. The NCI says studies have shown mixed results, and the NIH says it is not known whether aromatherapy helps with sleep.
Do essential oils have side effects?
They can. The NCI names allergic reactions, skin irritation and sun sensitivity with some oils, and NIEHS reports hormone-like activity for lavender and tea tree oil in lab studies.
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