Essential oil ingestion, D-limonene

Dr. James Geiger, MD


My initial clinical aromatherapy training and certification, which was based on U.K. teaching advised that ingestion of essential oils (EO) was not an appropriate methodology. I considered this recommendation reasonable at the time because in my profession, anesthetic medications can also be described to have potential risk of toxic reactions, having defined toxic therapeutic ratios (LD50).

Current awareness of positive testimonies from people using protocols for ingesting EO lead me to search for and consider several new aromatic science references demonstrating proof of principle to document the safe and effective use of ingesting EO in humans in placebo controlled, randomized, double blind clinical trials. There are currently three different studies for diseases in which ingested EO have been proven to be safe and have positive benefits when taken internally; d-limonene from citrus for breast cancer, cineole from eucalyptus for asthma and lavender for anxiety.

Plants are teleologically designed medicinal foods and are artistically qualified by their signature shapes to show us how they can attend to specific organs of the human body. Walnuts look like the brain and when shelled intact even have a bridge between the two “cerebral” hemispheres. Walnuts contains oil of omega-3 fatty acids to augment brain function. The root of ginger looks like the intestines and works well  on  disorders  causing  gastrointestinal  issues.  The  citrus  family,  e.g.  oranges,  and grapefruit are likened to breasts and contribute to the metabolic health of adipose, lymphatic, cellular and humoral immune systems.

Wellness practitioners of the art and aromatic science of medical aromatherapy in the 21st Century are gaining informative molecular biology studies and human clinical trials for EO on which to base clinical decisions. There are challenging co-existing medical conditions, like cancer, that convey significant implications, risks and benefits, when considering the use of complementary wellness methodologies, like aromatherapy.

Generally  regarded  as  safe  EOs  are classified  as food  supplements,  according  to  the  FDA. Approximate possible percentages of D-limonene in distilled essential oils citrus peel.

95% grapefruit 90% orange 70% lemon 45% lime 40% bergamot.

Human studies showing the impact of dietary supplements on chemotherapy effectiveness are not required  for  products  marketed  as  supplements.   The  chemotherapy  effects  of  free  radicals and antioxidants effects of EO have clinical components. Studies have shown that patients receive benefits when treated with certain antioxidants with or without chemotherapy and radiation. These three specific antioxidants interfere with three specific conventional cancer therapeutics in vivo: flavonoids with tamoxifen, N-acetyl-cysteine with doxorubicin, and beta-carotene with 5-fluorouracil.

Certain antioxidants are prescribed for some patients during cancer treatment to  reduce the side effects of chemotherapy. The use of these antioxidants does not  reduce the effectiveness of cisplatin, cyclophosphamide,  or  ifosfamide  in  the  treatment  of  cancer.  Two  prescription antioxidants, mesna (Mesnex) and amifostine (Ethyol), can be prescribed to specifically prevent the side effects of the cancer chemo drugs ifosfamide, cyclophosphamide, and cisplatin. These two antioxidants are for prescription use only; they have been evaluated in human studies by the Food and Drug Administration (FDA) and are approved for use in this cancer chemotherapy setting.

Citrus peel contains the chemical constituents of essential oils that reduced the risk of squamous cell carcinoma of the skin. Evidence like lavender’s linalool, a plant-derived mono-terpene alcohol, showing reversal of doxorubicin resistance in  human breast adenocarcinoma cells, has stimulated much mono- terpene research.

Many monoterpene chemicals like D-limonene from citrus peel have been patented since the late 90s. The metabolic engineering of the synthesis of EO in plants to increase the quantity and quality of specific EO, is a growing industry involving molecular genetics. There are specific chemical reactions that occur, coinciding   with   the   intra-cellular   EO   chemical   constituents,   having   crossed   lipid  membranes, interactively recognizing genes within the nucleus and organelles, like the chloroplast and mitochondria.

“Limonene is a bioactive food component found in citrus peel oil that has demonstrated chemopreventive and chemotherapeutic activities in preclinical studies. Limonene was found to preferentially concentrate in the breast tissue.We conclude that limonene distributed extensively to human breast tissue and reduced breast tumor cyclin D1 expression that may lead to cell cycle arrest and reduced cell proliferation. Further placebo-controlled clinical trials and translational research are warranted to establish limonene’s role for breast cancer prevention or treatment.”

Human breast tissue disposition and bioactivity of limonene in women with early-stage breast cancer.

Miller JA, Lang JE, Ley M, Nagle R, Hsu CH, Thompson PA, Cordova C, Waer A, Chow HH. Cancer Prev Res (Phila). 2013 Jun;6(6):577-84.


D limonene is one example of single terpene therapy with known breast cancer prevention and therapy application. Therapies with triterpenes and sesqiterpenes and with mutli-terpene therapies in particular could be proven to be the most effective prevention and treatments for diseases by offering a broad- spectrum approach to bodily systems. This integrative practice, could be best represented by each plant’s whole essential oil, especially an essential oil that is pure containing the highest percentage therapeutic chemical constituents. The synergistic blending of these essential oils, in various orders, could provide varieties of cellular response, repair, and regeneration through multiple molecular pathways such as receptor agonism and antagonism, biomarker augmentation, modulation of oxidative stresses, and intra- nuclear genetic mechanisms involving the transcription and translation of genetic material and proteins.



D-Limonene: An emerging antineoplastic agent.

Kapoor S. Hum Exp Toxicol. 2013 May 28.

Implication of limonene and linalyl acetate in cytotoxicity induced by bergamot essential oil in human neuroblastoma cells.

Russo R, Ciociaro A, Berliocchi L, Cassiano MG, Rombolà L, Ragusa S, Bagetta G, Blandini F, Corasaniti MT. Fitoterapia. 2013 May 23.

Oral administration of d-Limonene controls inflammation in rat colitis and displays anti -inflammatory properties as diet supplementation in humans.

d’Alessio PA, Ostan R, Bisson JF, Schulzke JD, Ursini MV, Béné MC. Life Sci. 2013 May 7.

Safety evaluation and risk assessment of d-Limonene.

Kim YW, Kim MJ, Chung BY, Bang du Y, Lim SK, Choi SM, Lim DS, Cho MC, Yoon K, Kim HS, Kim KB, Kim YS, Kwack SJ, Lee BM.

J Toxicol Environ Health B Crit Rev. 2013;16(1):17 -38.

Human breast tissue disposition and bioactivity of limonene in women with early-stage breast cancer.

Miller JA, Lang JE, Ley M, Nagle R, Hsu CH, Thompson PA, Cordova C, Waer A, Chow HH. Cancer Prev Res (Phila). 2013 Jun;6(6):577-84.

Suppression of MAPK and NF-κB pathways by limonene contributes to attenuation of lipopolysaccharide-induced inflammatory responses in acute lung injury.

Chi G, Wei M, Xie X, Soromou LW, Liu F, Zhao S. Inflammation. 2013 Apr;36(2):501-11.

Induction of apoptosis by D-limonene is mediated by inactivation of Akt in LS174T human colon cancer cells.

Jia SS, Xi GP, Zhang M, Chen YB, Lei B, Dong XS, Yang YM. Oncol Rep. 2013 Jan;29(1):349-54.

D-Limonene modulates T lymphocyte activity and viability.

Lappas CM, Lappas NT. Cell Immunol. 2012 Sep;279(1):30-41.

D-limonene rich volatile oil from blood oranges inhibits angiogenesis, metastasis and cell death in human colon cancer cells.

Chidambara Murthy KN, Jayaprakasha GK, Patil BS. Life Sci. 2012 Oct 5;91(11-12):429-39.

Dietary d-limonene alleviates insulin resistance and oxidative stress-induced liver injury in high-fat diet and L-NAME -treated rats.

Victor Antony Santiago J, Jayachitra J, Shenbagam M, Nalini N. Eur J Nutr. 2012 Feb;51(1):57-68.