Essential oils (EOs) are a concentrated, hydrophobic fraction derived from aromatic plants that contain multiple chemical constituents that may have biologic activity.1 EOs are used in perfumery, as flavoring agents, and in aromatherapy for their therapeutic or relaxing properties. The chemical composition for an individual EO varies based on growing conditions of the plant and from which part of the plant the fraction was derived.

Numerous in vitro studies and some animal studies suggest that many different chemical constituents of EOs have anticancer properties. In-human studies have evaluated the use of EOs in a supportive role, and though EOs appear to have some efficacy in this setting, larger studies are needed to confirm their effects.

In-Human Studies

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Several small in-human studies have evaluated the effect of inhaled or topically applied EO preparations to prevent radiation-induced toxicities. A study of 24 women undergoing radiotherapy for breast cancer demonstrated that an EO preparation that contained helichrysum (Helichrysum augustifolium), frankincense (Boswellia cateri), lavender (Lavandula angustifolia), and geranium (Pelargonium graveolens) EOs dissolved in jojoba, aloe vera, tamanu, and primrose oils was equivalent to the standard of care ointment (RadiaPlexRx) for skin assessments, quality of life, and patient satisfaction.2

Another small study found that gargling with an EO preparation that contained manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides) dissolved in water prolonged the onset of radiation-induced mucositis, reduced pain, decreased oral symptoms, and decreased weight loss among patients with head and neck cancers compared with gargling with water alone or usual care.3 Patients undergoing radioactive iodine treatment for differentiated thyroid cancer who inhaled lemon and ginger EOs demonstrated significantly better accumulation rates of the parotid and submandibular glands (P < .05), and a significant increase in secretion by bilateral parotid glands compared with the control group (P < .05).4

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Inhaled aromatherapy with ginger EO present in a necklace significantly decreased chemotherapy-induced acute nausea (P = .04), but not delayed nausea or vomiting compared with a fragrance-matched artificial placebo.5 Patients who inhaled the EO also experienced a significant improvement in global health status (P < .001), role functioning (P = .002), and appetite (P < .001) compared with placebo.

Animal Studies

Several animal studies using primarily orthotopic mouse models suggested that EOs have anticancer properties.1 EOs from pimientillo (Xylopia frutescens), thyme (Thymus broussonetii), Verbenaceae (Lippia gracilis), Guatteria pogonopus, neem, and Lamiaceae (Mesosphaerum sidifolium) inhibited tumor growth, and EOs from Cuban oregano (Plectranthus amboinicus) and Brazilian pepper tree (Schinus terebinthifolius Raddi) prevented metastasis.1,6 Cancer prevention was noted with EOs derived from pomegranate and sage (Salvia libanotica).