During the last decade, there has been a growing interest in aromatherapy, which uses essential oils as major therapeutic agents to improve a variety of health conditions (Aćimović, 2021; Ali et al., 2015). Nowadays, it is recognized as aroma science therapy (Esposito et al., 2014) and existing scientific studies suggest that aromatherapy is effective in reducing levels of anxiety and stress (Lee et al., 2011; Fellowes et a., 2008), depression (Firoozei et al., 2021; Sánchez-Vidaña et al., 2017), dental anxiety (Cai et al., 2021) and acute pain (Lamadah & Nomani, 2016; Mirzai et al., 2009; Tafazoli et al., 2011). In addition, aromatherapy has been proven effective in the treatment of sleep disorders (Cheong et al., 2021; Song et al., 2021), rheumatic diseases (Barão Paixão & De Carvalho, 2021), and has demonstrated anti-inflammatory effects (Ali et al., 2015; Park et al., 2014). Given those promising results, it is essential to know what aromatherapy is and how it can be used effectively.
In a wider sense, aromatherapy is defined as the therapeutic use of plant-derived concentrated essences which are extracted by distillation (Herz, 2009; Perry & Perry, 2006). It refers to the practice of using essential oils extracted from bark, flowers, stems, roots, leaves, or other parts of a plant to improve the physical and emotional well-being of the general population. Recently, different authors (Aćimović, 2021; Hermann et al, 2019) classified the essential oils used in aromatherapy in seven main groups, based on the aroma and particular smell of the oil.
Essential oils contain volatile natural compounds that are considered to exert a pharmacological effect by penetrating the body by oral, dermal (aromatherapy massage) (Buckle, 2003), and/or olfactory administration (inhalation aromatherapy) (de Groot & Schmidt, 2016). Thus, aromatherapy can be applied through three main methods:
Among them, inhalation aromatherapy is increasingly recognized as an accessible, easy-to-use, and effective method for stress relief and mood enhancement (Alexander, 2001). Although the exact neurological mechanisms of aromatherapy have not been established, and there are several differing results in the research in this field, inhaled air with essential oils:
Although inhaled aromatherapy cannot cure major illnesses, it has shown efficacy in reducing the levels of stress and anxiety in a variety of situations and conditions. Nowadays, a variety of controlled studies with strong research methodology and good samples sizes, have shown the utility of inhaled essential oils for stress relief and anxiety reduction in the general population (Haehner et al., 2017; Ndao et al., 2012; Seyyed-Rasooli et al., 2016; Tugut et al., 2017; Ueki et al., 2014), persons with cancer (Ozkaraman et al., 2018; Pimenta et al., 2016; Redd et al., 1994; Yayla & Ozdemir, 2019), cardiovascular disease (Fazlollahpour-Roni et al., 2019; Hasanzadeh et al., 2016; Moslemi et al., 2019; Najafi et al., 2014), chronic renal failure (Barati et al., 2016) or dental problems (Lehrner et al., 2000; 2005). Inhalation aromatherapy has also shown benefits during painful medical procedures like a diagnostic curettage (Bakhsha et al., 2014; Eslami et al., 2018; Dagli et al., 2019).
In this sense, the John Hopkins Medicine (2020) recommends to use of essential oils in these forms:
From the above studies, it is possible to conclude that essential oils are natural and non-invasive methods that can help to regulate the mood and the affect in humans. In contrast, some common alternatives can have detrimental effects on users’ health.
First, synthetic fragrances are made from chemicals of which 95% are derived from petroleum and include toluene, according to the Environmental Working Group (EWG). Precisely, toluene has adverse effects on the Central Nervous System (CNS), cardiovascular, hematopoietic, reproductive, and respiratory systems, as well as on the liver, kidneys, skin, and sensory organs after exposure to high concentrations (Kopelovich et al., 2015). Toluene can cause urothelial and bladder cancers (Adamowicz et al., 2019). Phthalate esters have been also identified in synthetic fragrances (U.S. Food and Drug Administration, 2020), which can also contribute to the development of urothelial cancer in patients with chronic kidney disease (Huan & Chou, 2018). Thus, several studies suggest that the use of synthetic fragrances can have important health risks for the consumers.
Second, recent studies have shown that scented candles, especially the cheaper varieties, can also have a negative impact on health. In particular, authors like Ahn et al. (2015) identified a total of 34 compounds in scented candles, including potentially carcinogenic formaldehyde and aromatic hydrocarbons such as toluene and benzopyrene. Thereby, it is important to note that scented candles release pleasant aromas but also toxic components before lighting (off) and when lit (on).
The use of synthetic fragrances and scented candles has been found to have serious consequences on health. Given this context, healthy alternatives include the use of unscented candles made of 100% beeswax or pure essential oils.
Finally, note that recent research studies have demonstrated the viability and the utility of combining essential oils with emergent technologies such as Virtual Reality (VR). In particular, the combination of aromatherapy and VR shows efficacy in improving the wellbeing of patients undergoing chemotherapy (Oyama et al., 2000), reducing the stress in the general population (Hedblom et al., 2019; Kaimal et al., 2020), and reducing stress and promoting a positive mood in older institutionalized adults (Cheng et al., 2020). Those studies suggest that aromatherapy, as an established therapeutic, can be combined with and made more efficacious through the use of the latest emerging technologies such as VR.
In addition, the use of essential oils during exposure to virtual scenarios could provide help in alleviating simulator sickness. This is a side effect that some VR-users can experience which is characterized by dizziness, sweating and, especially, nausea. The use of essential oils have been demonstrated to block the serotonin and dopamine receptors in the central nervous system involved in nausea (Ahmadi et al, 2020). After inhalation, essential oils are absorbed through the lungs, the nasotracheal mucosa and by the bloodstream and exert their effects by acting on the limbic system. Given this context, recent studies have shown the efficacy of inhalation aromatherapy in reducing the severity of nausea in a variety of conditions such as in surgical patients (Ahmadi et al., 2020; Ferruggiari et al., 2012), postoperative settings (Briggs et al., 2016; Fearrington et al., 2019), chemotherapy processes (Zorba & Ozdemir, 2018), acute care settings (Johnson et al., 2016), among others.
In particular, although more research is still needed, current studies suggest that essential oils like peppermint (Abdel Ghani & Ahmed Ibrahim, 2013; Ahmadi et al. 2020; Briggs et al., 2016; Fearrington et al., 2019; Lane et al., 2012; Tate, 1997), ginger (Ernst & Pittler, 2000; Fearrington et al., 2019; Hunt et al., 2013; Johnson et al., 2016: White, 2007) and lavender (Abdel Ghani & Ahmed Ibrahim, 2013) can be effective to reduce nausea. Researchers have been also using Essential Oils in a blend form, since they are believed to be more effective as the therapeutic value is caused by the reaction and balance of the essential oils constituents (Ryman, 1993). Thus, for example, Zorba & Ozdemir (2018) used a blend of peppermint, bergamot and cardamom, while Hunt et al. (2013) used a blend of peppermint, ginger, spearmint ,and cardamom. In a similar way, Ovayuly et al. (2014) used a blend of lavender, mint, chamomile, jasmine, violet, rosemary.
Those studies suggest that the use of inhalation essential oils may also prevent and alleviate nausea and dizziness in virtual worlds. However, specific research is still needed to explore the influence of essential oils on the simulator sickness experienced in immersive worlds.
Given the positive effect of essential oils on mental health, Relax VR has designed and created a specific essential oils blend for each of its virtual natural scenes. The essential oils of Relax VR are 100% natural and contain no synthetic fragrances or chemicals.
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