How Do Essential Oils Work and What Are the Health Benefits?

Aromatherapy, the use of essential oils to improve health, is a popular and natural form of alternative medicine. In 2023, the global market of essential oils was valued at 23.7 billion U.S. dollars. But what evidence supports the use of essential oils, and are they safe?

What are essential oils?

Essential oils are natural oils derived from plants that capture their core aroma or ‘essence.’ Their use dates as far back as ancient India, Persia, and Egypt. Throughout history, essential oils have served various functions ranging from medicinal to cultural and spiritual.

Since they come from nature, essential oils differ from synthetic fragrances, which contain aromatic compounds manufactured by humans in the laboratory. Some synthetic fragrances contain a mix of human-made and natural compounds.

Essential oils have a variety of uses today. They are found in many cosmetics, household products, and even food. This article explores the popular use of essential oils as an alternative form of medicine, a practice called aromatherapy.

How do essential oils work?

Aromatherapy is the use of essential oils — typically through inhalation or direct application to the body — for their healing properties. In very select cases, essential oils are found in ingestible dietary supplements.

When you inhale essential oils, specialized cells in your nose called olfactory receptors detect the presence of molecules present in the oils. The olfactory receptors relay this message through the olfactory nerve to a collection of brain structures called the limbic system.

The limbic system is involved in many functions, including regulating emotions, influencing behaviors, forming memories, and controlling unconscious bodily processes through hormones and the autonomic nervous system. Therefore, by stimulating the limbic system, essential oils can have many psychological and physiological impacts.

Essential oils can also travel either through the skin, respiratory system, or gastrointestinal system into the bloodstream, where they can affect cells and tissues throughout the body. Laboratory experiments have shown that essential oils have antimicrobial (including antibacterial and antifungal), antioxidant, and anti-inflammatory properties, which may lead to positive health outcomes in the body’s circulation.

Types of essential oils

Over a hundred different types of essential oils exist. Here, we include five popular essential oils and their most notable health benefits.

Lavender

Lavender, known for its calming effects, is commonly used to improve mental and emotional health. Research shows that lavender essential oil can improve anxiety symptoms, reduce stress, and alleviate symptoms of depression. It is also frequently used as a sleep aid as it has been shown to improve sleep quality. Therefore, one of the optimal times to use lavender may be at night before bed.

Peppermint

Peppermint’s claim to fame is in its use for digestive problems. It has been shown to relieve symptoms of irritable bowel syndrome and functional dyspepsia, a condition marked by bloating, indigestion, and abdominal pain. Importantly, peppermint should not be used for acid reflux, as it worsens heartburn symptoms.

Peppermint essential oil has also been shown to provide relief for tension headaches and migraine headaches.

Tea tree oil

Tea tree oil is most famous for its antimicrobial properties. It is most commonly applied to the skin to treat common wounds or bacterial and fungal infections. Another common use is as a mouthwash to help with oral health. Importantly, tea tree oil should not replace the use of antibiotics for serious infections. When in doubt, speak with your doctor.

Eucalyptus

Due to its soothing properties, eucalyptus is best known for its effects on the respiratory tract. Eucalyptus essential oil helps to relieve cold symptoms such as cough and stuffy nose, which explains why it is a common ingredient in cold and cough products. Eucalyptus can also improve breathing and relieve asthma symptoms in some people.

Lemongrass

Like many essential oils, lemongrass may have a variety of health effects, and no one stands out in particular. Lemongrass has been shown to fight bacteria and fungi and alleviate anxiety. Studies in animals show that lemongrass may have the potential to treat stomach ulcers and lower cholesterol, although these findings need to be confirmed in human studies.

What are the health benefits of essential oils?

Most essential oils have multiple uses when it comes to modifying health. The following are four health-related benefits seen with essential oils.

Boosts mental health

Essential oils have been shown to improve mood and relieve symptoms of stress and anxiety.

For instance, lemon oil has been shown in animal studies to affect the levels of feel-good chemicals in the brain, including norepinephrine, dopamine, and serotonin.

A 2023 systematic review concluded that essential oils are effective in reducing anxiety, with the most recommended being citrus oil. Another 2017 systematic review demonstrated that essential oils, particularly when used in massage therapy, may reduce symptoms of depression.

Improves sleep

A 2021 systematic review showed that inhalation of essential oils may lead to improvements in sleep among people with mild sleep disturbances, including insomnia. The best-studied essential oil for its sleep-promoting properties is lavender.

There are many different ways to use essential oils to help with sleep, including spraying essential oils onto your pillow or mattress, diluting and rubbing small amounts onto your neck and forehead, mixing them into a bedtime lotion, or taking an aromatic bath before bed.

Relieves pain

A 2016 systematic review of evidence from animal models concluded that aromatherapy may be effective in reducing pain. This was attributed to essential oils' ability to affect brain pathways involved in the detection and perception of pain. However, studies on humans were outside of the scope of this review.

Pain relief may also be due to the anti-inflammatory properties of essential oils. Some popular essential oils used for pain relief include rosemary, chamomile, eucalyptus, and lavender. Blends of multiple essential oil types are also commercially available.

A 2016 systematic review of human studies demonstrated that both acute pain types (e.g., menstrual pain, pain related to childbirth, postoperative pain), as well as chronic pain types (e.g., back, neck, or knee pain), appear to respond to aromatherapy. However, the evidence favors the treatment of acute over chronic pain. Additionally, essential oils do not appear to be effective for pain due to neuropathy.

For their use in pain relief, essential oils can be diluted and either inhaled or applied to painful areas such as joints and muscles (such as during massage therapy). They can also be a nice addition to a warm bath or added to a warm or cool compress.

Destroys germs

While essential oils should never replace medical evaluation and adherence to medical therapy, several essential oils may be useful for treating mild infections and sanitizing objects. Essential oils contain compounds called aldehydes and phenols, which possess antimicrobial properties.

Tea tree oil, in particular, has shown effectiveness in treating acne, dandruff, and athlete’s foot. It is also a good alternative to chlorhexidine-based mouthwashes for improving gingivitis. Tea tree oil can be diluted with a carrier oil and applied to problem areas such as the face, scalp, or feet. You can also find commercial products such as shampoos, lotions, and creams with tea tree oil included in the appropriate amounts.

Laboratory studies show that other essential oils with lemongrass, eucalyptus, peppermint, and orange possess antibacterial activity against common viruses, bacteria, and fungi. This makes them potentially useful as home disinfectants.

Note that essential oils should never replace medications in treating more serious infections.

Safe usage of essential oils

Since essential oils are highly concentrated, diluting them in a carrier oil is crucial for preventing skin irritation and other side effects. There are many different carrier oil options; some examples include jojoba, coconut, almond, and olive oil. Since oil and water do not mix, you should not dilute essential oils using water.

Guidelines vary, but the following rules of thumb are generally safe for adults:

• Application to the face: 6 drops of essential oil per 1 ounce of carrier oil.
• Application to the hair or body: 12 drops per 1 ounce of carrier oil.
• For baths: 10–20 drops per 1 ounce of carrier oil.
• Usage in a diffuser: no dilution is necessary. Simply add a few drops of essential oil to water inside the diffuser according to the manufacturer’s instructions.

For pregnant women or those with sensitive skin, use a lower dilution ratio when applying to any part of the skin: 3–6 drops of essential oil per 1 ounce of carrier oil.

The available research shows that aromatherapy is generally safe to use in pregnancy, although pregnant women should not ingest essential oils due to their unknown risks in this population. Pregnant women should also avoid certain essential oils that carry a high risk for toxicity or that may affect the pregnancy. This includes sweet birch, wintergreen, cinnamon, clove, rose, and clary sage.

Importantly, many essential oils are not recommended for young children due to the risk of allergic reactions and toxicity. There is also limited research on the safety and benefits of essential oils in children. Always consult with a pediatrician before allowing your child to use essential oils.

Do essential oils expire?

Essential oils do not ‘expire’ in the same way that food spoils. However, they do change and lose their effectiveness over time. When exposed to heat, light, and oxygen, essential oils undergo a process called oxidation that changes the structure of the molecules found in the oils. It is unclear whether essential oils are safe to use once they have undergone extensive oxidation.

To be on the safe side, only use essential oils that have not passed their shelf life, which ranges anywhere from 1–5 years, depending on the essential oil.

Risks and side effects of essential oils

The most common side effect of essential oils is skin irritation due to improper dilution. After an essential oil has been diluted properly, it is important to first test only a small amount on the skin. Citrus oils — including lemon, orange, and bergamot — can potentially cause the skin to burn and blister in direct sunlight.

The strong scents of essential oils can trigger difficulty breathing in some people, particularly those with an underlying lung condition such as asthma or chronic obstructive pulmonary disease.

Those who are sensitive to smell can also experience nausea or headaches when inhaling essential oils.

Some essential oils, particularly lavender and peppermint, can be found in dietary supplements. While these are generally safe to take as directed, you should discontinue them and seek medical care if you experience any side effects. You should never attempt to ingest essential oils directly due to the risk of toxicity.

As a word of caution, the safety of essential oils is not entirely understood because they are not regulated by the Food and Drug Administration in the same ways that medicines are. Some research suggests that essential oils can be harmful to health. In a small study, long-term use of essential oils impaired heart and lung function.

Essential oils have also been shown to disrupt hormone pathways in the body. While the consequences are unclear, there is some connection between essential oils and the development of abnormal breast growth in adolescents.

How to choose the right essential oils?

It is important to use only high-quality essential oils as low-quality products are not only ineffective but also potentially more unsafe due to the presence of synthetic compounds.

You can be more confident that you are using a pure, high-quality essential oil if the following are true:

• The label contains the Latin name of the plant used to make the oil, as well as the parts of the plant that were used, how it was extracted, and how it was grown
• The label lists only one ingredient, signifying its simplicity
• The label does not contain the word ‘fragrance,’ as this indicates the presence of synthetic compounds
• The essential oils have undergone third-party testing (look for ‘gas chromatography and mass spectrometry’ or ‘GC/MS’), and the company provides these details

When used safely, essential oils can potentially improve multiple aspects of health and well-being. However, it is important to recognize that some research findings are mixed, and not everyone will benefit from essential oils. If you decide to try essential oils for yourself, use only pure, high-quality products and follow all proper application instructions.