What Are Phytoncides & Why You HAVE To Know More- Essential Oil Lover Or Not!

Mamma's garden

Who doesn’t love Saturday!? One of my rituals on Saturday is listening to some of my favorite podcasts as I work out and do yoga.

Today I was listening to Ben Greenfield’s podcast. His topic was on the stress and anti-inflammatory hormone, cortisol. I became inspired to learn more on one of the highlighted suggestions, phytoncides, to modulate cortisol from the interview. Specifically, his expert guest discussed a study in men that demonstrated that the phytoncides of an essential oil, cypress, reduced cortisol levels!

Very cool!

So, I had to dive in, geek-out, and postpone my day trip to Whole Foods for a bit. Check out what I learned below.




So, you may be wondering, “what the heck is a phytoncide and how does this relate to essential oils?”

Interestingly, it seems like this term has been around in research for over 70 years. I found this 1960 article on the “bacteriostatic” benefit of onion’s phytoncide on E. coli. (1)

Don’t worry, I’m answering your question next.


Phytoncide Defined

According to one article, “Phytoncide, a volatile essential oil produced by plants and trees, has not only anti-microbial activity, but also a stress- relieving effect.”

In fact, this same article, found in the journal Fibers and Polymers, described an invention that aimed to capitalize on a time-released method of phytoncide release, “We prepared a sheath/core type melt-spun fiber that releases phytoncide for a prolonged time. The fiber is comprised of a nylon sheath and a polypropylene (PP) core material.” (2)


The Relaxing Effects of Phytoncides Explored In Rodents

Another article defined phytoncides, “as the antimicrobial volatile organic compounds emitted from plants. In chemical terms, the main components of phytoncide are closely related to essential oils produced from plants.”

This study actually tested the effects of these components on mice and concluded that these volatile compounds, found in Japanese spruce oil, produced relaxing and stress-relieving effects in the rodents tested. Interestingly, so did one of its constituents alone, the famous monoterpene, d-limonene:

Forest-air bathing and walking (shinrin-yoku) is beneficial to human heath. In this study the phytoncide (volatile compounds) released from Cryptomeria japonica plantation forest was characterized by using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The main volatile compounds were a-pinene (19.35%), b-myrcene (16.98%), D-limonene (15.21%), and g-muurolene (7.42%). Furthermore, the neuropharmacological activity of the essential oils from leaves of C. japonica (ECJ) was evaluated by several animal behavior tests. ECJ could prolong the sleeping phase of ICR (imprinting control region) mice in the pentobarbital-induced sleeping time model. Furthermore, both EJC and one of its monoterpenes, D-limonene, possessed potent anxiolytic and analgesic activities based on the results obtained from elevated plus maze and writhing tests. The volatile compounds released from C. japonica provide relaxing and stress-relieving effects on mice, and further study on the effect of phytoncide on humans is worthwhile. (3)


An earlier study showed benefits in stress relief in rats as well. Specifically, it reported that phytoncides may lower blood pressure and stress hormones in the stroke-prone spontaneously hypertensive creatures (poor rodents):

1. Phytoncides are volatile substances released mainly from trees. We studied whether phytoncides can reduce stress responses in stroke-prone spontaneously hypertensive rats (SHRSP). 2. Under the restraint stress, SHRSP exposed to phytoncides showed lower blood pressure than those without the exposure (186.8 +/- 3.9 vs 207.7 +/- 3.4 mmHg, respectively, P < 0.01 by Student’s t-test). 3. Consistent with the observation above, the plasma concentration of catecholamines under the restraint stress was lower in the phytoncides group than in the control group. 4. Based on these results, we concluded that phytoncides reduced the cardiovascular response to restraint stress in SHRSP. (4)


The Immune Response Of Phytnocides (In Vitro )

An in vitro study sought to determine if the benefits of “forest bathing” on immune function was related to phytoncides (wood essential oils).

The researchers concluded that they significantly enhanced a type of immune cell activity:

Phytoncides significantly increase cytolytic activity of NK-92MI cells in a dose-dependent manner and significantly increase the expression of perforin, granzyme A, and granulysin in the NK-92MI cells. Phytoncides also partially, but significantly, restore the decreased human NK activity and the decreased perforin, granzyme A, and granulysin expression in NK-92MI cells induced by dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organophosphorus pesticide. Pretreatment with phytoncides partially prevents DDVP-induced inhibition of NK activity. Taken together, these data indicate that phytoncides significantly enhance human NK activity and this effect is at least partially mediated by induction of intracellular perforin, granzyme A, and granulysin. (5)


Another study demonstrated antioxidant and microbe inhibiting effects of these compounds:

Physiological activities of four types of phytoncide solutions (A, AB, CY and D-types), prepared from various plants widely distributed in nature, were examined. We assayed these phytoncide solutions, testing for active oxygen inhibition, DPPH radical scavenging effects, nitrogen monoxide inhibition, and lipid peroxide inhibition. The AB- and D-types of phytoncide solutions especially showed comparably potent antioxidant effects. Antibacterial and antifungal assays were conducted using the AB- and D-types, with results showing significant inhibitory activities with these solutions. (6)


Skin Health (In Vitro)


An in vitro study on human fibroblast cells demonstrated the protective effects against reactive oxygen species with the use of phytoncides. (7)


Furthermore, another study demonstrated inhibitory effects of phytoncide solutions on rodent and human melanoma cells. (8)


Medical Applications

One study even suggested the use of phytoncides as an alternative to medication in drug-eluting stents for cardiovascular patients. This was due to the “antioxidant, antimicrobial, and anti-inflammatory” effects of monoterpenoids:

A drug-eluting stent (DES) is one of the commonly used treatment techniques in percutaneous coronary intervention (PCI). Sirolimus (SRL) has been widely used for DES as a drug for suppressing neointimal hyperplasia causing restenosis. Phytoncides (PTC) are compounds released from trees and plants, and their solutions contain monoterpenoids such as a-pinene, careen, and myrceen. Some studies have reported that these components exhibit antioxidant, antimicrobial, and anti-inflammatory activities. We hypothesized that PTC may become an alternative drug to SRL for DES, exhibiting alleviated side effects as compared to SRL. A PTC-incorporated stent was compared with an SRL-incorporated stent in terms of physicochemical, pharmacokinetic, and biological properties. In in vitro studies, the effects of each drug on cells were investigated. The results showed that both drugs exhibited similar cytotoxicity, anti-inflammation, and antiproliferation effects. However, these effects resulted from different mechanisms associated with cells, as seen in the immunofluorescence result. An in vivo assay showed that the lumen area was significantly larger and the neointimal area was significantly smaller in SRL- and PTC-loaded stents compared to a drug-unloaded stent. These results suggest that phytoncide can be a feasible alternative drug to SRL for advanced DES although more studies are needed. (9)


Pig Protection

A weaning pig study showed that phytoncides assisted with healthy growth, decreased diarrhea, and with optimizing the animals’ microbiome, blood profiles, and nutrient scores. How is this medical? Two words.. antibiotic resistance. (10)


Human Studies

This study stemmed from a previous one that showed a two night trip to the forest enhanced natural-killer (NK) cell activity and intracellular anti-cancer proteins in lymphocyte tests. Furthermore, the effect was reported to last for 7 days after the trip. The city dwellers in the control group did not exhibit the same effect.

We previously reported that a forest bathing trip enhanced human NK activity, number of NK cells, and intracellular anti-cancer proteins in lymphocytes. In the present study, we investigated how long the increased NK activity lasts and compared the effect of a forest bathing trip on NK activity with a trip to places in a city without forests. Twelve healthy male subjects, age 35-56 years, were selected with informed consent. The subjects experienced a three-day/two-night trip to forest fields and to a city, in which activity levels during both trips were matched. On day 1, subjects walked for two hours in the afternoon in a forest field; and on day 2, they walked for two hours in the morning and afternoon, respectively, in two different forest fields; and on day 3, the subjects finished the trip and returned to Tokyo after drawing blood samples and completing the questionnaire. Blood and urine were sampled on the second and third days during the trips, and on days 7 and 30 after the trip, and NK activity, numbers of NK and T cells, and granulysin, perforin, and granzymes A/B-expressing lymphocytes in the blood samples, and the concentration of adrenaline in urine were measured. Similar measurements were made before the trips on a normal working day as the control.

The authors explored what may account for the difference (bold emphasis mine):

Phytoncide concentrations in forest and city air were measured. The forest bathing trip significantly increased NK activity and the numbers of NK, perforin, granulysin, and granzyme A/B-expressing cells and significantly decreased the concentration of adrenaline in urine. The increased NK activity lasted for more than 7 days after the trip. In contrast, a city tourist visit did not increase NK activity, numbers of NK cells, nor the expression of selected intracellular anti-cancer proteins, and did not decrease the concentration of adrenaline in urine. Phytoncides, such as alpha-pinene and beta-pinene were detected in forest air, but almost not in city air. These findings indicate that a forest bathing trip increased NK activity, number of NK cells, and levels of intracellular anti-cancer proteins, and that this effect lasted at least 7 days after the trip. Phytoncides released from trees and decreased stress hormone may partially contribute to the increased NK activity. (11)

female friends in fallA follow-up study reproduced the above study’s conclusion a few years later, this time measuring phytoncides in the forest, including an additional phytoncide, isoprene. (Remember, isoprene units make up essential oil constituents such as monoterpenes, sesquiterpenes, and phenylpropenoids). The abstract reads (bold emphasis mine):

Similar measurements were made before the trip on a weekend day as the control. Phytoncide concentrations in the forest were measured. The day trip to the forest park significantly increased NK activity and the numbers of CD16(+) and CD56(+) NK cells, perforin, granulysin, and granzyme A/B-expressing NK cells and significantly decreased CD4(+) T cells, the concentrations of cortisol in the blood and adrenaline in urine. The increased NK activity lasted for 7 days after the trip. Phytoncides, such as isoprene, alpha-pinene, and beta-pinene, were detected in the forest air. These findings indicate that the day trip to the forest park also increased the NK activity, number of NK cells, and levels of intracellular anti-cancer proteins, and that this effect lasted for at least 7 days after the trip. Phytoncides released from trees and decreased stress hormone levels may partially contribute to the increased NK activity. (12)


Below is the study I found that Ben’s guest discussed (bold emphasis mine):

We previously reported that the forest environment enhanced human natural killer (NK) cell activity, the number of NK cells, and intracellular anti-cancer proteins in lymphocytes, and that the increased NK activity lasted for more than 7 days after trips to forests both in male and female subjects. To explore the factors in the forest environment that activated human NK cells, in the present study we investigate the effect of essential oils from trees on human immune function in twelve healthy male subjects, age 37-60 years, who stayed at an urban hotel for 3 nights from 7.00 p.m. to 8.00 a.m. Aromatic volatile substances (phytoncides) were produced by vaporizing Chamaecyparis obtusa (hinoki cypress) stem oil with a humidifier in the hotel room during the night stay. Blood samples were taken on the last day and urine samples were analysed every day during the stay. NK activity, the percentages of NK and T cells, and granulysin, perforin, granzyme A/B-expressing lymphocytes in blood, and the concentrations of adrenaline and noradrenaline in urine were measured. Similar control measurements were made before the stay on a normal working day. The concentrations of phytoncides in the hotel room air were measured. Phytoncide exposure significantly increased NK activity and the percentages of NK, perforin, granulysin, and granzyme A/B-expressing cells, and significantly decreased the percentage of T cells, and the concentrations of adrenaline and noradrenaline in urine. Phytoncides, such as alpha-pinene and beta-pinene, were detected in the hotel room air. These findings indicate that phytoncide exposure and decreased stress hormone levels may partially contribute to increased NK activity. (13)

Another study demonstrated a similar effect with a phytoncide mixed with pine and cypress. Specifically, this mixture was found to decrease blood pressure and cortisol in 60 college students. (Note: the control group was nonequivalent):

Asian college studentsPURPOSE: The purpose of this study was to identify the effects of the phytoncides on serum cortisol level, vital signs and life stress of college students. METHODS: This study was nonequivalent control group non-synchronized design. The subjects consisted of 60(control group: 28, experimental group: 32). The phytoncides mixed the pine(pinus sylvestris) oil with the cypress(cupressus sempervirens) oil in the same rate. In the experiment, it was put in an aroma-necklace bottle and inhaled 3 times per day(9AM, at noon, before going to bed) for 2 weeks. The data were analyzed by the SPSS version 12.0 program. RESULTS: In the experimental group systolic BP(F=15.603, p=.000), diastolic BP(F=29.489, p=.000) and serum cortisol level(F=4.968, p=.000) were significantly decreased. CONCLUSION: The phytoncides inhalation is a partly help to reduce college students’ life stress. The phytoncides is the incense of the familial tree. We recommended to examine what differences between the green shower and the phytoncides inhalation for the stress reduction. (14)


Major Takeaways:

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  1. I love the term phytoncide, though it kind of sounds like a sci-fi word.
  2. The impact of different components in plants is astounding. Using essential oils with all the constituents, especially ones high in monoterpenes, can have synergistic and calming effects.
  3. If you can’t get outdoors to decrease stress and assist with immune balance, why not diffuse tree essential oils. Some of my favorites: Sacred Mountain, pine, cypress, Idaho balsam fir, palo santo. Okay, they are all my favorites. (This takeaway is dedicated to my new colleagues who are big fans of my diffuser.)


Now, I want your feedback. Does smelling oils keep you as calm as an outdoor adventure? Let me know!


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Disclaimer: This information is applicable ONLY for therapeutic, Grade A essential oils. This information DOES NOT apply to essential oils that have not been AFNOR and ISO standardized or tested for purity. There is no quality control in the United States and oils labeled as “100% pure” need only contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin.

This information is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness



(1) Vrba, M. Morphological changes of cells ofescherichia coli caused by a phytoncide from onion. Folia Microbiologica. June 1960, (5)3:198-200

(2) Lee JY, Oh SJ, Lee MS, Park JY, Rye JJ, Lee KH. Preparation of phytoncide-emitting nylon/PP sheath/core fiber and the release profile of phytoncide. Fibers and Polymers. 2012; 13(9). DOI: 10.1007/s12221-012-1209-2

(3) Cheng W-W, Lin C-T, Chu F-H, Change S-T, Wang S-Y. ChangeNeuropharmacological activities of phytoncide released from Cryptomeria japonica. Journal of Wood Science. February 2009; 55(1):27-31.

(4) Kawakami K1, Kawamoto M, Nomura M, Otani H, Nabika T, Gonda T. Effects of phytoncides on blood pressure under restraint stress in SHRSP. Clin Exp Pharmacol Physiol. 2004 Dec;31 Suppl 2:S27-8.

(5) Li Q, Nakadai A, Matsushima H, Miyazaki Y, Krensky AM, Kawada T, Morimoto K. Phytoncides (wood essential oils) induce human natural killer cell activity. Immunopharmacol Immunotoxicol. 2006;28(2):319-33.

(6) Abe T, Hisama M, Tanimoto S, Shibayama H, Mihara Y, Nomura M. Antioxidant effects and antimicrobial activites of phytoncide. Biocontrol Sci. 2008 Mar;13(1):23-7.

(7) Fujimori H, Hisama M, Shibayama H, Iwaki M. Protecting Effect of Phytoncide Solution, on Normal Human Dermal Fibroblasts against Reactive Oxygen Species. J.Oleo Sci. 2009; 58(8): 429-436.

(8) Fujimori H, Hisamab M, Shibay H, Kawase A, Iwaki M. Inhibitory Effects of Phytoncide Solution on Melanin Biosynthesis. Bioscience, Biotechnology, and Biochemistry. 2010; 74(5). DOI:10.1271/bbb.90700

(9) Kang SN, Kim SE, Choi J, Park K, Goo JH, Sim DS, et al. Comparison of phytoncide with sirolimus as a novel drug candidate for drug-eluting stent.. Biomaterials. 2015 Mar;44:1-10. doi: 10.1016/j.biomaterials.2014.12.015. Epub 2015 Jan 5.

(10) Zhang S, Jung JH, Kim HS, Kim BY, Kim IH. Influences of Phytoncide Supplementation on Growth Performance, Nutrient Digestibility, Blood Profiles, Diarrhea Scores and Fecal Microflora Shedding in Weaning Pigs. Asian-Australasian Journal of Animal Sciences. 2012;25(9):1309-1315. doi:10.5713/ajas.2012.12170.

(11) Li Q1, Morimoto K, Kobayashi M, Inagaki H, Katsumata M, Hirata Y, Hirata K, Suzuki H, Li YJ, Wakayama Y, Kawada T, Park BJ, Ohira T, Matsui N, Kagawa T, Miyazaki Y, Krensky AM. Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. Int J Immunopathol Pharmacol. 2008 Jan-Mar;21(1):117-27.

(12) Li Q, Kobayashi M, Inagaki H, Hirata Y, Li YJ, Hirata K, Shimizu T, Suzuki H, Katsumata M, Wakayama Y, Kawada T, Ohira T, Matsui N, Kagawa T. A day trip to a forest park increases human natural killer activity and the expression of anti-cancer proteins in male subjects. J Biol Regul Homeost Agents. 2010 Apr-Jun;24(2):157-65.

(13) Li Q. Kobayashi M, Wakayama Y, Inagaki H, Katsumata M, Hirata Y, Hirata K, Shimizu T, Kawada T, Park BJ, Ohira T, Kagawa T, Miyazaki Y. Effect of phytoncide from trees on human natural killer cell function. Int J Immunopathol Pharmacol. 2009 Oct-Dec;22(4):951-9.
(14) Nam ES, Uhm DC. Effects of Phytoncides Inhalation on Serum Cortisol Level and Life Stress of College Students.  J Korean Acad Adult Nurs. 2008 Oct;20(5):697-706. Korean.

images courtesy istockphoto.com and mom’s garden