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Abstract
We should remember the widespread beneficial and practical uses of tea tree oil in aromatherapy and cosmetics worldwide. Tea tree oil is now under regulatory threat from the European Union. In the following article some important arguments are raised that reveal other sides to important aspects of this discussion. The results of two PhD theses, a comprehensive literature study report and a survey about the use of the oil could help to avoid a total and unwarranted prohibition of tea tree oil.
... Essential oils (EO) are natural, microbiologically active substances with an extensive spectrum of activity [9]. Due to the acceptance of PLA and EO by the American Food and Drug Administration as "Generally Recognized As Safe GRAS", a significant development of studies of materials based on the above-mentioned compounds has taken place [10]. Ahmed et al. in their works described the results of detailed research devoted to films based on polylactide (PLA) with the addition of cinnamon oil [11,12]. ...
... As a result, it can be applied to effectively combat different types of respiratory and oral cavity infections, as well as skin diseases, and supports wound healing [5]. It should be stressed that TTO also exhibits antiinflammatory, antiviral, antioxidant, antiseptic and antifungal properties [10]. The antibacterial potential of tea tree essential oil is mainly related to the presence of terpinen-4-ol and 1,8-cineole [8]. ...
The aim of the study was to establish the influence of poly(ethylene glycol) (PEG) on the properties of potential biodegradable packaging materials with antibacterial properties, based on polylactide (PLA) and tea tree essential oil (TTO). The obtained polymeric films consisted of PLA, a natural biocide, and tea tree essential oil (5–20 wt. %) was prepared with or without an addition of 5 wt. % PEG. The PLA-based materials have been tested, taking into account their morphology, and their thermal, mechanical and antibacterial properties against Staphylococcus aureus and Escherichia coli. It was established that the introduction of a plasticizer into the PLA–TTO systems leads to an increase in tensile strength, resistance to deformation, as well an increased thermal stability, in comparison to films modified using only TTO. The incorporation of 5 wt. % PEG in the PLA solution containing 5 wt. % TTO allowed us to obtain a material exhibiting a satisfactory antibacterial effect on both groups of representative bacteria. The presented results indicated a beneficial effect of PEG on the antibacterial and functional properties of materials with the addition of TTO.
... It has been reported that the components of essential oils easily convert into one another through various interactions such as oxidation, isomerisation, polymerization, disproportionation, cyclization or dehydrogenation reactions which may be triggered either enzymatically or chemically (Börje et al., 2004). Aside from natural conversion that has been reported to possibly take place in the plant, shown by the constituents obtained from plants harvested at different age or stage of maturity, as well as different times and seasons (Burfield, 2004;Figueiredo et al., 2008), this is also known to occur during storage of essential oils (Wabner et al., 2006;Oladimeji and Orafidiya, 2007;Bråred-Christensson et al., 2009;. As a result of this occurrence, there have been concerns expressed on the biological activities of certain essential oils following long term storage (Oladimeji and Orafidiya, 2007;. ...
... The inter-conversions of components of the essential oil of O. gratissimum L. on rapid autooxidation has been reported . Although this investigation does not confirm that these differences were due to the storage of the oil, similar changes have been reported in the constituents of essential oils from other plants on storage (Wabner et al., 2006;Oladimeji and Orafidiya, 2007;. ...
... Significant studies were conducted using PLA polymer and EO since both compounds were accepted by the FDA as "Generally Recognized As Safe GRAS". 432 EOs contain different antibacterial compounds making biodegradable films, activated with these antimicrobial agents, particularly effective against postprocessing infection and valuable to extend the shelf life of food. 433 Besides being perceived as safe for consumption, 434 EOs are recognized to be able to reduce the water vapor permeability of films owing to their lipidic nature. ...
The diseases caused by microorganisms are innumerable existing on this planet. Nevertheless, increasing antimicrobial resistance has become an urgent global challenge. Thus, in recent decades, bactericidal materials have been considered promising candidates to combat bacterial pathogens. Recently, polyhydroxyalkanoates (PHAs) have been used as green and biodegradable materials in various promising alternative applications, especially in healthcare for antiviral or antiviral purposes. However, it lacks a systematic review of the recent application of this emerging material for antibacterial applications. Therefore, the ultimate goal of this review is to provide a critical review of the state of the art recent development of PHA biopolymers in terms of cutting-edge production technologies as well as promising application fields. In addition, special attention was given to collecting scientific information on antibacterial agents that can potentially be incorporated into PHA materials for biological and durable antimicrobial protection. Furthermore, the current research gaps are declared, and future research perspectives are proposed to better understand the properties of these biopolymers as well as their possible applications.
... There have been concerns expressed on the biological activities of certain essential oils following storage (Wabner et al., 2006). This is more important as it has been documented that exposure to light, oxygen, heat and cold leads to a wide variety of chemical reactions and interactions in the constituents of essential oils resulting in their modifications and breakdowns on storage (Figueiredo et al., 2008;Burfield, 2004;Bråred-Christensson et al., 2009). ...
... The statement of Guenther (1948), considering moisture to have a higher impact on essential oil spoilage than light, was not supported in the published literature and might be based on acid-catalyzed reactions at higher temperatures. Moreover, while Wabner and others (2006) and Našel (2009) suggested not to keep essential oils in the refrigerator based on elevated POVs analyzed in tea tree oil, other studies revealed that degradation reaction in essential oils were altogether promoted at room temperature (see above) (El-Wakeil and others 1986; El-Nikeety and others 1998; Turek and Stintzing 2012; Turek and others 2012). In summary, most degradation events described in the literature were elicited either by light, temperature, or a combination of both and a copresence of oxygen (Hausen and others 1999; Misharina and others 2003; Hagvall and others 2007). ...
In recent years, consumers have developed an ever-increasing interest in natural products as alternatives for artificial additives or pharmacologically relevant agents. Among them, essential oils have gained great popularity in the food, cosmetic, as well as the pharmaceutical industries. Constituting an array of many lipophilic and highly volatile components derived from a great range of different chemical classes, essential oils are known to be susceptible to conversion and degradation reactions. Oxidative and polymerization processes may result in a loss of quality and pharmacological properties. Despite their relevance for consumers, there is a paucity of information available addressing this issue. Therefore, the present review provides a comprehensive summary on possible changes in essential oils and factors affecting their stability. Focusing on individual essential oils, the various paths of degradation upon exposure to extrinsic parameters are outlined. Especially temperature, light, and oxygen availability are recognized to have a crucial impact on essential oil integrity. Finally, analytical methods to assess both genuine as well as altered essential oil profiles are evaluated with respect to their suitability to track chemical alterations. It is believed that only a careful inspection of essential oils by a set of convenient methods allows profound quality assessment that is relevant to producers and consumers alike.
... Most prominently, the POV in pine oil stored for 72 weeks in the dark (storage A) was found to be almost 43 times higher than the initial value, which therefore presents the highest increase from all essential oils analyzed in this study (Fig. 1c). In contrast, Fig. 1c reveals distinctively lower POVs assessed in the course of storage under accelerated storage conditions (light, 38°C, storage C) compared to values obtained at room temperature (storage A or B), while on the other hand, the rise in conductivity together with the pH drop was most pronounced at storage C. Correspondingly, Wabner, Geier, and Hauck (2006) found higher POVs in essential oils stored in the fridge than at room temperature. The authors explained their results by the increased solubility of gas at lower degrees centigrade (Henry's law), hence a lower concentration of oxygen present at elevated temperatures. ...
Four common essential oils were subjected to different storage conditions in order to reveal the impact of light and temperature on the physico-chemical properties as well as on the chemical composition of the respective oil. For this purpose, aliquots of lavender, pine, rosemary, and thyme oil were stored for up to 72 weeks in the presence of atmospheric oxygen at 23 °C in the dark as well as at 23 °C and 38 °C under cool white light, respectively. Alterations were monitored by a set of recently established quality parameters such as peroxide value, pH, and conductivity as well as high-performance liquid chromatography (HPLC) with diode array detection and tandem mass spectrometry. Characteristic changes occurred for each essential oil, revealing individual impacts of extrinsic parameters on the particular sample. Most striking degradation of monoterpenes could be observed in rosemary oil: While α-terpinene was reduced to less than 10% within 3 weeks of storage at 38 °C under daylight but did not alter during the same period at room temperature in the dark, its amount in pine oil decreased to about 40 and 65%, respectively. Moreover, trends of peroxide values were compared to conductivity and pH in the course of storage. This approach allows to shed light on the storage history thereby providing a more complete view on essential oil quality. Additionally, gas chromatography (GC) analyses coupled to electron ionization mass spectrometry were performed in order to evaluate the informative and complementary character of GC and HPLC with regard to their capability to retrace essential oil modifications upon storage, respectively.
The oxidation stability of oils extracted from castor seed was evaluated. The extraction was conducted by the Soxhlet method using ethanol, n-hexane, petroleum ether and supercritical carbon dioxide (SC-CO2) as solvents. For this purpose, castor oils derived from these extraction methods were heated in an oven at 70°C for 0-12 weeks. Minor components such as free fatty acids (FFAs) obtained by different extraction methods were investigated. The quality and oxidative stability of oil recovered by SC-CO2 was generally found to be better than those recovered by the Soxhlet method. To determine alteration in oxidation stability during storage, six analytical measurements were performed: peroxide value (PV), refractive index (RI), pH, conductivity, acid value (AV) and FFA. The oxidative stability data obtained from this study had the following range of average values for ethanol, n-hexane, petroleum and SC-CO2 extracted oil, respectively: peroxide values of 12.4-48.7, 3.3-36.3, 3.5-35.2 and 0.41-1.23 meq/kg; RIs of 1.4771-1.4776, 1.4770-1.4778, 1.4770-1.4779 and 1.4773-1.4774; pH values of 3.64-3.34, 4.60-4.41, 4.54-4.31 and 6.72-6.67; conductivity levels of 15.8-49.1, 14.5-46.4, 14.3-46.9 and 11.4-16.4 μs/cm; AVs of 1.6-3.8, 0.6-- 1.4, 0.53-1.10 and 0.22-0.28 mg KOH/g; and FFA values of 0.8%-1.9%, 0.3%-07%, 0.27%-0.55% and 0.11%-0.14%. This implies that the parameters considered offers an appropriate tool for evaluating castor oil quality and oxidative stability, and it sheds light on the different responses of castor oils during storage.
Essential oils from lavender, pine, rosemary, and thyme were stored at different sampleto-
air volume ratios for up to twelve weeks in the dark at room as well as refrigerator
temperatures. Alterations were comprehensively monitored by determination of peroxide
value as well as assessment of pH and conductivity which have been recently established
as essential oil quality parameters. In doing so, the individual character of each
essential oil was revealed as samples were shown to respond differently to oxygen availability
and temperature variation, respectively. While peroxide formation in essential oil
from rosemary and pine was promoted at higher temperature, oxygen solubility played
a more decisive role for the peroxide level present in lavender and thyme oil, respectively.
Moreover, detection of stable polar oxidation products was achieved by combined
conductivity and pH analysis, pinpointing an advanced state of oxidation. Thus, more
complete light was shed on the distinct storage history complementing the hitherto well
introduced peroxide value. Comprehensive stability studies considering both preliminary
as well as later oxidation stages for individual essential oils are therefore suggested to
obtain an even more complete view on essential oil quality.
The second edition of this book is virtually a new book. It is the only comprehensive text on the safety of essential oils, the first review of essential oil/drug interactions, and it provides detailed essential oil constituent data not found in any other text. Much of the existing text has been re-written, and 80% of the text is completely new. There are 400 comprehensive essential oil profiles and almost 4000 references. There are new chapters on the respiratory system, the cardiovascular system, the urinary system, the digestive system and the nervous system. For each essential oil there is a full breakdown of constituents, and a clear categorization of hazards and risks, with recommended maximum doses and concentrations. There are also 206 Constituent Profiles. There is considerable discussion of carcinogens, the human relevance of some of the animal data, the validity of treating an essential oil as if it was a single chemical, and the arbitrary nature of uncertainty factors. There is a critique of current regulations.
Aus vielen Untersuchungen an Versuchstieren wie auch an Menschen geht klar hervor, dass Duftstoffe das Verhalten und das Wohlbefinden beeinflussen. Die Einsatzgebiete für Raumbeduftung sind vielfältig und erstrecken sich längst nicht mehr nur auf den privaten Bereich, sondern auch auf mehr oder weniger öffentliche Räume wie Büros, Hotels oder Warenhäuser, um nur einige Beispiele zu nennen. Je nach Einsatzort bedarf es dabei verschiedener, auf Räumlichkeit und Zweck zugeschnittener, Beduftungs- bzw. Luftreinigungstechnologien. Dabei wird oft außer Acht gelassen, dass Duftstoffe, so nützlich und wohltuend ihre Anwendung auch sein mag, dennoch ein gewisses Potential für unerwünschte Wirkungen besitzen. Dieses Risiko ist umso größer, wenn Duftstoffe mangelhafter Qualität ohne einschlägiges
Fachwissen und unhinterfragt eingesetzt werden. Menschen, bei denen der Kontakt mit Duftstoffen als Folge dieser Praxis bereits zu gesundheitlichen Problemen geführt hat, müssen Duftstoffe ihr Leben lang meiden. Als Konsequenz dieser leider unerfreulichen Entwicklung gibt es bereits ausgesprochene Duftstoffgegner, die versuchen dem Trend der ubiquitären Beduftung entgegenzuwirken. Der Schutz der Bevölkerung geht vor, und so versucht auch die EU die Sicherheit von Riechstoffen durch Neuregelungen zu verbessern und das Risiko für die Konsumenten zu minimieren. Nichtsdestotrotz sind die Fortschritte im Bereich der Technik und der Chemie, sowohl was die Raumbeduftung als auch was die Verbesserung der Luftqualität angeht, viel versprechend. So können auch sensible Menschen einen Vorteil aus der Forschung in diesem Bereich ziehen. In diesem Aufsatz werden die Möglichkeiten und Einsatzgebiete der Raumbeduftung aufgezeigt und ihre Stärken und Schwächen beschrieben.
Gerüche prägen genauso wie visuelle, akustische und haptische Eindrücke das Stadtbild und begleiten Bewohner und Besucher bei ihren tagtäglichen Erlebnissen und Verrichtungen. Das Ziel der hier beschriebenen Untersuchungen war zu überprüfen, ob Gerüche, die mit der Stadt Wien in Verbindung gebracht werden, mit emotional gefärbten, autobiographischen Erinnerungen verknüpft sind, ob diese Gerüche im Labor auf wenige, chemische Bestandteile reduziert werden können, die ihre olfaktorischen Eigenschaften ausreichend reproduzieren, und ob mit diesen synthetischen Geruchsmischungen im Labor spezifische physiologische Reaktionsmuster ausgelöst werden können, die mit den ursprünglich assoziierten Basisemotionen korrespondieren. Um diese Fragen zu beantworten wurden im ersten Teil dieser Untersuchung 50 Wiener und Wienerinnen zu subjektiven, emotionalen Erinnerungen und damit verknüpften Gerüchen befragt. Konkret wurde nach Erinnerungen gefragt, die mit Trauer, Wut, Freude, Überraschung, Angst und Ekel (den sog. Basisemotionen) in Zusammenhang standen und bei denen ein bestimmter Geruch eine Rolle spielte. Dabei zeigte sich kein eindeutiger Zusammenhang zwischen autobiographisch relevanten Stadtgerüchen und den Basisemotionen. Daher wurden im zweiten Teil der Untersuchung sechs Gerüche ausgewählt, die von einem kleinen Teil der Befragten spezifisch mit einer der sechs Emotionen assoziiert worden waren. Diese Gerüche wurden im Hinblick auf ihre „character impact compounds“, also ihre geruchsprägenden Inhaltsstoffe, analysiert, und im Labor wenig komplexe Duftmischungen hergestellt, die die olfaktorischen Eigenschaften der Gerüche zufriedenstellend darstellten. Im dritten Teil der Untersuchung wurden diese Duftmischungen schließlich 30 jungen, gesunden Versuchspersonen präsentiert, und Reaktionen des autonomen Nervensystems auf die Geruchsreizung gemessen. Es konnten keine für die sechs Basisemotionen charakteristischen physiologischen Reaktionsmuster beobachtet werden, aber es zeigte sich, dass die autonomen Kennwerte, insbesondere die Hautleitfähigkeit, die Gerüche nach ihrer hedonischen Valenz differenzierten: Angenehme Gerüche waren mit einem geringeren autonomen Arousal assoziiert als unangenehme Gerüche. Diese Ergebnisse bestätigen teilweise Befunde aus früheren Untersuchungen zur Verbindung zwischen emotionalen Erinnerungen und Gerüchen. Die fehlende Spezifität der Verbindung zwischen Stadtgerüchen und Basisemotionen kann am besten durch die starke individuelle Komponente der autobiographischen Gedächtnisinhalte erklärt werden.
Several analytical methods including high-performance liquid chromatography (HPLC) were applied on essential oils to establish a set of suitable quality parameters for monitoring changes during storage. For this purpose, 7 essential oils derived from various plant families were exposed to possible worst-case conditions for up to 3 mo at 38 °C under cool white light in the presence of atmospheric oxygen. After storage and immediate freezing at –80 °C to stop further alterations until analysis, individual physicochemical parameters were assessed and are discussed with regard to the precision of the respective method as well as suitability to monitor aging processes. To determine conductivity and pH values, a work-up of essential oils by water extraction was established. Conductivity, peroxide value as well as pH turned out to be suitable parameters to picture alterations. Additionally, HPLC fingerprints were monitored by diode array detection to track underlying chemical changes in essential oil composition.
Practical Application: This study evaluates a set of analytical parameters to track changes during essential oil storage. On this basis, quality alterations can be monitored.
The essential oil of Australian tea tree (Melaleuca alternifolia) has been investigated for skin irritancy using an occlusive patch test on 25 human subjects for 21 days. 1,8-Cineole, the constituent reported as being responsible for tea tree oil skin irritancy, was similarly tested. Irritancy was not detected from any of eight preparations containing pure cineole in concentrations of 0.0, 3.8, 8.0, 12.0, 16.0, 19-9, 24.0 and 28.1% in soft white paraffin. Eight tea tree oil preparations containing similar concentrations of cineole did not show skin irritation when tested at 25% in soft white paraffin. However, 3 of 28 panelists were withdrawn from the trial because of a severe allergic (as distinct from irritant) response to tea tree oil. These subjects were then tested with either pure tea tree oil major constituents or crude fractions. One panelist showed a strongly positive reaction to α-terpinene and all three reacted (two strongly) to two sesquiterpenoid fractions. None showed allergic response to α-pinene, β-pinene, limonene, p-cymene, 1,8-cineole, γ-terpinene, terpinolene, terpinen-4-ol or α-terpineol in 24-28 h. Three positive reactions occurred to a sesquiterpene hydrocarbon fraction, and one to a sesquiterpene alcohol fraction. The significance of these human tests with the topical application of tea tree oil products is discussed and methods for the minimization of allergens are suggested.
An investigation of the in vitro mutagenic potential of a variety of commercially available and widely used tea tree essential oils was performed. The mutagenic potential of tea tree oil (Melaleuca alternifolia) was examined using the Histidine Reversion Assay (Ames Test). One of the major components, the monoterpenoid terpinen-4-ol, was also examined to determine if it demonstrated any mutagenic potential. Salmonella typhimurium (TA102, TA100 and TA98) was utilised in the Ames test.
Commercially available tea tree oils were tested. Despite a previous report demonstrating a possible mutagenic trend in a single commercially available tea tree product, no mutagenic effect was determined in any of the brands of tea tree oil on any of the strains of Salmonella examined with or without metabolic activation. The same negative results were obtained for the terpinen-4-ol component examined. There was a clear evidence of toxicity of tea tree oil on all Salmonella strains and also by terpinen-4-ol at higher dose levels. It is suggested that terpinen-4-ol may contribute significantly to the widely reported antibacterial activity of tea tree oil.
Background: Topical tea tree oil has become increasingly popular as a general-purpose medicament for various dermatological conditions. Although recent reports of adverse cutaneous reactions have highlighted concerns about the risk of inducing acute allergic contact dermatitis, few published studies have attempted to evaluate objectively the true irritancy and allergenicity potential of this commonly used essential oil. Objective: To perform predictive testing for irritancy and allergenicity of tea tree oil in a large group of human subjects. Methods: Various concentrations of tea tree oil (5, 25, 100%) in different vehicles were applied under occlusive patch testing to the skin of healthy, human volunteers (n = 311) using a protocol based on the Draize human sensitisation test. Patch test sites were assessed every 48 h and scored according to the severity of any resulting cutaneous reaction using a clinical grading scale from 0 to 4 over a 21-day induction period. After a 14-day rest period, subjects underwent challenge testing with the same tea tree oil samples to determine if sensitisation to tea tree oil had occurred. Results: The mean irritancy score for each test sample was low, ranging from 0 for 5% tea tree oil to 0.2505 for neat 100% tea tree oil. However, 3 subjects developed grade 3 skin reactions during the induction period suggestive of an allergic reaction. Conclusions: Topical application of tea tree oil is associated with negligible skin irritancy. In the group of subjects studied, the risk of developing an allergic dermatitis from topical tea tree oil usage was found to be
Tea tree oil, derived from Melaleuca alternifolia Cheel, has gained a steady and still increasing popularity. Among all alternative products introduced to the market since the beginning of the trend “back to nature” in the 1980s, it has survived for the longest time (ie, about 15 years). Although consumers feel that products from natural sources have fewer potential side effects, it has been shown that tea tree oil causes allergic contact dermatitis. Case reports have been published since 1991.1 In 1999, the contact allergens of tea tree oil (TTO) were identified., 2 Sixteen constituents were shown to play roles as sensitizers. Fresh TTO was revealed to be a very weak sensitizing material. However, TTO kept in open or closed bottles or other containers or incorporated as an ingredient in an herbal product undergoes photo-oxidation within weeks to months, owing to light, warmth, and moisture. These factors lead to the creation of degradation products that are moderate to strong sensitizers. For example, TTO kept on the windowsill of a bathroom and opened daily for use shows a remarkable increase in the peroxide number within a few days. Peroxides, epoxides, and endoperoxides of its main constituents (the monoterpenes) are formed. The older the oil becomes, the more of these products are concentrated in the altered oil. The number of its primary compounds diminishes while the concentrations of the newly created substances increase. In contrast to freshly obtained oil, oxidized TTO possesses a high sensitizing potency., 2
Tea tree oil, a distillation product of the Australian tea tree (Melalence alternitolia) is increasingly used as an alternative remedy for various dermatological diseases. Tea tree oil contains several allergenic monoterpenes and sesquiterpenes. In this multicenter study it was evaluated, whether the increasing use of tea tree oil has lead to an increased frequency of sensitization in Germany and Austria which would justify its inclusion into the standard series.
For patch testing a standardized tea tree oil was used, dissolved 5% in diethylphtalate (DEP). Consecutive patients of 11 dermatological departments in Germany and Austria were tested. Readings were taken on day 2 and 3 according to the guidelines of the German Contact Dermatitis Research Group (DKG).
5% tea tree oil was positive in 36/3375 patients (1.1%). Sensitization frequencies showed great regional variations and ranged from 2.3% (Dortmund), 1.7% (Buxtehude), 1.1% (Essen), 0.7% (Graz), to 0% (Berlin, Vienna). 14/36 patients (38.9%) also showed a positive patch test reaction to oil of turpentine.
Our results show that tea tree oil is an important contact allergen for some centers. It should be tested, if medical history suggests its previous use. Considering the great regional differences in frequencies of sensitization its inclusion into the standard series is not recommended yet.
Tea tree oil is the essential oil steam-distilled from Melaleuca alternifolia, an Australian native plant. In recent years it has become increasingly popular as an antimicrobial for the treatment of conditions such as tinea pedis and acne.
To investigate the anti-inflammatory properties of tea tree oil on histamine-induced weal and flare.
Twenty-seven volunteers were injected intradermally in each forearm (study and control assigned on an alternating basis) with histamine diphosphate (5 microg in 50 microL). Flare and weal diameters and double skin thickness were measured every 10 min for 1 h to calculate flare area and weal volume. At 20 min, 25 microL of 100% tea tree oil was applied topically to the study forearm of 21 volunteers. For six volunteers, 25 microL paraffin oil was applied instead of tea tree oil.
Application of liquid paraffin had no significant effect on histamine-induced weal and flare. There was also no difference in mean flare area between control arms and those on which tea tree oil was applied. However, mean weal volume significantly decreased after tea tree oil application (10 min after tea tree oil application, P = 0.0004, Mann-Whitney U-test).
This is the first study to show experimentally that tea tree oil can reduce histamine-induced skin inflammation.
Doktor-Arbeit Technische Universitä Mü Antimicrobial activity of tea tree oil against oral microor-ganisms
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Australisches teebaumö, oxidationsprodukte als mö ursache von kontaktdermatiden
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Zur Frage der Sensibilisierung durch a ¨therische O ¨ le
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Antiviral activity of tea tree oil
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The peroxide value, methods and use
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Questionnaire adverse reactions with tea tree oil
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