Uses, Types, and Side Effects of Essential Oils

Essential oils are highly concentrated plant extracts distilled into oil. A popular trend in complementary and alternative medicine, many people are drawn to the healing properties of these oils extracted from flowers, leaves, roots, and other parts of plants.

The use of essential oils for medicinal purposes dates back to ancient cultures. In fact, many modern medications have been derived from these oils. Continuing scientific research confirms a variety of health benefits for specific essential oils. However, while some oils are beneficial when used in small doses, other oils can be dangerous. 

Essential oils are not regulated by the U.S. Food and Drug Administration (FDA). If you choose to use essential oils for medicinal purposes, use with caution and consult a certified holistic healthcare professional. 


Essential oils are often used to ease stress, boost mood, relieve pain from headaches and migraines, get a better night's sleep, quell nausea, and even repel insects. The beneficial compounds in the oils are often delivered through three main pathways: inhalation, topical application to the skin, and oral ingestion.


Essential oils are typically extracted using steam distillation, a process that involves applying steam until only oil remains. Essential oils contain volatile compounds, which make up the strong, characteristic scent of the plant.

In aromatherapy, these volatile compounds are inhaled using either a drop of oil on a piece of cloth or jewelry or diffused into the air using an aromatherapy diffuser. Inhalation is the safest method for using essential oils

When the oils' molecules are inhaled, they are said to influence the nervous system and brain areas (such as the limbic system) and affect hormones, brain chemicals, metabolism, and other body functions.


Essential oils are sometimes applied to the skin directly. This can be useful for delivering oils to a specific problem area, such as a backache, wrist pain, or sinus troubles. However, the topical use of essential oils should be done with caution.

Essential oils can be irritating to the skin and should not be applied full-strength on the skin. They should be diluted in a carrier oil (such as almond, apricot kernel, or avocado oil) before being applied to the skin. 

Essential Oils That Irritate Skin

The following oils should never be applied directly to the skin, unless properly diluted.

  • Bay
  • Cinnamon
  • Clove
  • Citronella
  • Lemongrass
  • Oregano
  • Thyme

Always test essential oils on a small patch of skin before applying to a larger area.

Essential oils can also be found in soap, lotion, shampoo, and bath salts and may be used during massage, spa treatments, compress, or spot treatment.


Essential oils are sometimes ingested and can be used in cooking as flavorings or taken internally as medication. However, this should be done with caution. While many essential oils are safe in small doses, others can be poisonous if ingested. 

One problem with using essential oils internally is that the product is not regulated by the FDA and there are no universal standards for ensuring the quality of the oil. The National Association of Holistic Aromatherapy (NAHA) recommends purchasing oils from a reputable supplier who analyzes its products using gas chromatography-mass spectrometry (GC-MS), which tests for purity.

Essential oils should only be ingested under the care of a qualified essential oil therapist and safety guidelines for dilution must be followed. Essential oils are fat-soluble and should be ingested along with dietary fat.

Health Benefits

Essential oils can be used to treat many physical and emotional health issues. At the molecular level, these oils contain beneficial compounds like antioxidants, terpenes, and esters that may help to boost wellness.

The body of research on the health benefits of essential oils is growing, with several studies showing promise for the use of individual oils in the prevention and treatment of disease. However, many of these studies are limited to testing on animals and cell cultures. Large-scale clinical trials determining the effect of individual oils on specific health conditions is lacking and there is limited information available on effective dosages.

A 2018 study published in the Journal of Dietary Supplements evaluated the general health effects of supplements, herbs, and essential oils and found oils are as effective as other supplements in improving health. In particular, study participants reported improved immunity, reduced pain and anxiety, and more energy and mental clarity. Laboratory tests also found improved blood markers associated with cholesterol, diabetes, and heart disease.

Common Oils

There are dozens of different essential oils, each with its own unique smell and potential healing properties. Here is a closer look at some of the more common essential oils and their purported health benefits.

  • Basil: Distilled from the popular cooking herb, basil oil is believed to ease coughs and congestion, enhance mood, improve digestion, increase alertness, and soothe muscle aches.
  • Bergamot: The distinctive scent that gives Earl Grey tea its flavor, this citrus oil is used to relieve anxiety and is being studied for potential cholesterol-lowering properties.
  • Calendula: A relative of the marigold, calendula may ease skin ailments including rashes, wounds, yeast infections, and other skin irritations.
  • Carrot Seed: Used in cosmetics, this oil has antibacterial and anti-inflammatory properties.
  • Cedarwood: Used to treat hair loss, cedar or cedarwood oil may also ease stress and improve sleep.
  • Cinnamon: Research suggests the oil of this popular spice may improve circulation, ease stress, relieve pain, fight off infections, and improve digestion.
  • Citronella: A natural insect repellant, it may also aid in stress management and fatigue.
  • Clove: A hot and spicy oil, clove is used to treat toothaches and relieve pain.
  • Eucalyptus: The active ingredient in VapoRub, eucalyptus is commonly used to treat colds, congestion, and coughs, and is being studied for antibacterial benefits.
  • Frankincense: This Biblical oil is used in skincare products to treat dry skin and reduce the appearance of wrinkles, age spots, scars, and stretch marks.It is also being investigated as anti-cancer agent.
  • Geranium: Commonly used in skincare, research shows this floral oil has antimicrobial properties.
  • Grapefruit: This citrus oil is said to relieve hangovers and jet lag and is used to reduce stress, stimulate circulation, increase energy, enhance mood, and improve digestion.
  • Helichrysum: This oil has a medicinal scent and is said to reduce inflammation, promote the healing of wounds and burns, stimulate digestion, boost the immune system, and soothe body and mind.
  • Jasmine: A sweet-smelling floral oil, it is touted as a stress-reliever with potential to help treat skin conditions including aged and dry complexions, inflammation, oily conditions, and psoriasis.
  • Lavender: One of the most widely used essential oils, lavender is used for relaxation and to relieve insomnia.
  • Lemon: Said to boost mood and energy, this citrus oil relieves anxiety and may help promote weight loss.
  • Lemongrass: Used for stress-relief and boosting immunity, studies suggest this oil can treat dandruff and fungal infections, and ease anxiety, headaches, and upset stomach. 
  • Myrrh: A Biblical oil, Myrrh is believed to ease coughs and colds, soothe digestive discomfort, and boost immunity.
  • Neem: A natural insect repellant, neem is also used to treat nail fungus and acne.
  • Neroli: This sweet oil is used to relieve anxiety and may reduce blood pressure.
  • Orange: The bright citrus scent is used to boost energy and improve mood, and research suggests it can ease anxiety.
  • Patchouli: A musky scented oil popular in incense, research shows patchouli oil may improve sleep.
  • Peppermint: This popular oil is used for headaches, pain, and stomach issues like irritable bowel syndrome.
  • Rose: One of the more expensive essential oils, this highly prized soothing floral scent is said to ease stress and menstrual cramps.
  • Rosemary: Distilled from the cooking herb, the scent of rosemary essential oil is said to boost attention and focus and is being studies in the prevention of dementia.
  • Sandalwood: This fragrant earthy scent is popular in meditation centers and is believed to relieve anxiety and improve sleep.
  • Tea Tree: Used as for fungal skin infections and as a spot treatment for acne
  • Ylang Ylang: Used to relieve pain, reduce inflammation, improve mood, and enhance libido, research shows this oil may reduce blood pressure.

Possible Side Effects

When used as directed, essential oils have very few side effects or risks based on the delivery method. 

Inhaling the scent of essential oils is the safest way to use them and has a very small risk of side effects, which typically resolve when you leave the area. You can diffuse the scent into the air with a steam diffuser or placing a drop on a cloth or piece of jewelry designed to absorb essential oils.

The topical application of essential oils is generally safe, however, certain oils can cause a reaction that may include contact dermatitis, burns, and skin irritation. A patch test should always be done when using a new essential oil to see if you are sensitive to the oil. Certain oils—citrus in particular—increase photosensitivity and lead to skin burns if exposed to the sun. These include citrus oils, such as lemon, lime, grapefruit, bergamot, and tangerine. If using photosensitizing oil, such as lemon, lime, grapefruit, bergamot, and tangerine, stay out of the sun for 24 hours after application.

Ingesting essential oils is not always safe and depends on the oil. Many essential oils are FDA-approved as ingredients in food and fragrances and are labeled generally regarded as safe (GRAS). However, some oils can be toxic and only ingested under medical supervision. Use caution when ingesting essential oils and do not swallow large amounts.

Avoid using essential oils close to your eyes, genitals, or mucous membranes. Essential oils are fat-soluble. If you get an oil in your eyes or mucous membrane, you can dilute its strength using a carrier oil.

Like any health supplements, essential oils may interact with prescription medications when taken internally. Check with your doctor or pharmacist before combining any essential oil with medications.

Oils to Avoid in Pregnancy

Women who are pregnant should use essential oils with caution. The following oils are not safe for use during pregnancy, according to the International Federation of Professional Aromatherapists: 

  • Oregano 
  • Thyme 
  • Clove 
  • Cinnamon 
  • Cumin 
  • Aniseed 
  • Fennel 
  • Anise 
  • Sweet Birch
  • Wintergreen 
  • Sage 
  • Hyssop

Essential oils can degrade plastic and should only be used in devices designed for use with essential oils. Do not use essential oils in a humidifier, CPAP machine, or any other breathing device.

What to Look For

Essential oils are not regulated by the FDA and their quality varies widely from brand to brand. The most reputable suppliers analyze their products using gas chromatography-mass spectrometry (GC-MS).

Look for oils sold in dark amber or cobalt blue glass bottles with the plant’s Latin name on the label. Never buy essential oil products that are stored in plastic, as the oils can dissolve plastic and contaminate the oil. 

When purchasing oil for use in an essential oil diffuser, opt for undiluted oils. These are typically sold in bottles that are 15ml (0.5 fl oz) or smaller. For topical application over large areas of skin, such as massages, diluted oils are a better choice.

Essential oils should be stored in a cool, dark place to prevent spoiling or degrading. With proper storage and handling, essential oils have a shelf life of about a year.

Sold in natural health stores, pharmacies, online, and through multi-level marketing companies, essential oils are not FDA-approved to treat any medical condition.

Do not make healthcare decisions regarding the use of essential oils without consulting a certified aromatherapist. You can find a practitioner in your area on the National Association of Holistic Aromatherapist website.

There is no official standard, certification, or designation that is universally recognized. Terms like 100% pure or therapeutic grade are marketing terms.

The price of an individual essential oil depends on the plant's availability, the amount of plant material required, and the growing, harvesting, and manufacturing conditions needed to produce the oil.

Jasmine oil, for instance, costs more than many other oils due to the millions of blossoms needed to produce one kilogram of jasmine absolute oil.

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