Across the world, the essential oils industry was worth more than $7 billion as of 2017 and is expected to grow to the same amount in the U.S. alone by 2024. But what are essential oils? These highly potent substances are extracted from plants through a physical process, usually distillation or mechanical pressing. They’re often used for their aromatherapy benefits, but also can be used topically (on the skin) for various purposes. While the popularity of essential oils may just seem trendy, there is science-backed evidence of their health benefits. And scientists continue to recommend more research into essential oils benefits and risks. In the meantime, talk to your doctor about whether these complementary therapies might be right for you.
As with many essential oils, there are several types of lavender essential oil. Lavandula angustifolia is the most commonly used. Research has shown lavender essential oil to have bactericidal effects. In one study, lavender oil killed an abundant bacterium on human skin within 5 minutes. Lavender essential oil also was shown to be effective against yeast and viral pathogens associated with skin infections. Lavender aromatherapy has been shown to reduce insomnia, and research has supported its antioxidant and anti-inflammatory properties.
Studies have found lemon essential oil has numerous biological benefits, including as an antioxidant, analgesic (pain reducer), and insect repellent. In a study that compared lemon essential oil with DEET, a synthetic insect repellent, lemon oil was found to be an effective alternative to repel mosquitoes. It has also been shown to improve mood, concentration, memory and cognitive performance. Depending on the way it is extracted, lemon and other citrus essential oils can pose some risk of phototoxicity, a skin irritation that occurs when the oil is used topically and then exposed to sunlight. Expressed lemon oil is phototoxic, while distilled lemon oil is not.
Peppermint oil has been shown to increase alertness and to combat mental exhaustion and memory loss. Many studies have shown topical treatment with peppermint oil is effective against different types of pain, including tension headaches, neck pain, and even residual (sometimes excruciating) pain after a bout of shingles. In at least one study, topical application of diluted peppermint essential oil showed hair growth effects, including the number of hair follicles and the depth of the roots. This same study showed peppermint oil can be even more effective at promoting hair growth than minoxidil, a drug found in many brands of hair regrowth treatment for human baldness.
Like other citrus essential oils, the scent of bergamot oil has been shown to calm and improve mood. Studies have also found bergamot can offer pain relief and can help heal wounds. In at least one study, cold-pressed bergamot oil was tested for its effect on nine different bacteria. The study showed bergamot has strong antimicrobial activity. Other research has concluded that bergamot possesses antioxidant and antifungal properties. Pressed bergamot can be phototoxic, so if you use this one topically, stay out of the sun.
Also known as melaleuca essential oil, tea tree oil has been found to have insecticidal uses. It has long been used to kill head lice, and there is scientific evidence that backs its efficacy, which sometimes was even higher than that of the conventional permethrin treatment for lice. However, the American Academy of Pediatrics cautions against the use of tea tree oil on children because natural products, such as essential oils, are not regulated by the FDA. Tea tree oil has also shown antibacterial and anti-inflammatory properties, and it has been effective at fighting acne with fewer side effects than some over-the-counter acne medications.
There are various types of orange essential oil, including sweet orange and bitter orange, and many of the benefits overlap. Both types of orange oil have antioxidant, antifungal and antibacterial properties. Both have also been shown to reduce anxiety and calm the nerves. Aromatherapy using bitter orange oil was found in one study to reduce the severity of labor pain compared with a control group. Another study showed sweet orange oil (along with grapefruit and lemon essential oils) had anti-carcinogenic effects against leukemia cells. Orange essential oil carries a low risk of phototoxicity.
Frankincense oil has been used in aromatherapy for thousands of years. Religious worship services use it as incense, and research has confirmed the oil has natural antimicrobial properties and is useful as an air purifier. Studies have found boswellic acid, one of the main components of frankincense essential oil, has anti-tumor properties. In one study, researchers found frankincense oil suppressed bladder cancer cell growth, but did not harm normal bladder cells. These scientists suggested frankincense essential oil might be useful as an alternative treatment, but that more research is needed. There are several different types of frankincense essential oil, each having some distinct benefits.
While they are natural products, essential oils come with risks if used improperly. Essential oils are highly concentrated, so even those as mild as lavender oil come with potential adverse effects, including skin sensitivity or allergic reactions. Diluting essential oils in another oil, such as olive oil, is one way to help minimize the potential for adverse effects. Also, be aware of potentially dangerous reactions in children, especially toddlers, even when the oils are diluted. Peppermint oil, for example, can cause serious side effects when inhaled, even for older children. Scientists have noted that essential oils can have negative interactions with other medications or medical conditions. These researchers emphasize that people use the same precautions with essential oils as they would with pharmaceutical drugs. Always talk to your doctor before using essential oils or any other alternative therapy.
The short answer: not always. Animals have different ways of metabolizing substances that they inhale or absorb through their skin than humans do. Essential oils can be dangerous for some animals, depending on their respiratory and metabolic systems. Never use essential oils on or around cats, birds or reptiles. These pets do not have the enzymes needed to safely metabolize essential oils. Dogs and horses may be able to tolerate essential oils in some cases, but be sure to use them under the care of a veterinarian trained in aromatherapy.