The influence of aromatherapy on stress – neurobiological mechanisms through the olfactory nerve pathway

The Effect of Aromatherapy on Stress - Neurobiological Mechanisms

Stress, often called the "silent killer," poses a significant health threat. Chronic stress contributes to dysregulation of neurohormonal axes, particularly the hypothalamic-pituitary-adrenal (HPA) axis, leading to elevated levels of cortisol and other stress hormones, as well as disruptions in the nervous and immune systems.[1][2] Consequences can include cardiovascular disease, metabolic disease, and mental disorders.

In the face of these threats, there is growing interest in complementary methods that alleviate emotional tension. One such method is aromatherapy – the therapeutic use of natural essential oils, which can influence mood and the body's stress response through the sense of smell.[3][4] Volatile aroma compounds inhaled from the oils enter the nose and stimulate olfactory receptors, initiating a neural signal transmitted directly to the brain via the olfactory nerve pathway. Due to this pathway's unique connections with emotional centers, aromatherapy is a promising approach to reducing stress and anxiety.

Anatomy of the olfactory nerve and its connections to the limbic system

The olfactory nerve (cranial nerve I) is responsible for transmitting olfactory stimuli from the nose to the brain. Its pathway begins in the olfactory epithelium of the nasal cavity, where approximately 50 million olfactory neurons equipped with receptors on cilia perceive odor molecules.[5][6] The axons of these neurons form olfactory filaments that pass through the cribriform plate to the olfactory bulb, a structure at the front of the brain. The first stage of signal processing occurs in the bulb: axons of olfactory neurons form synapses with mitral and tufted cells in the olfactory glomeruli, with each glomerulus responding to specific odorant molecules.[7] The mitral cells then send stimulation to further brain regions along the olfactory tract.

Unlike other senses, the olfactory tract is the only one that reaches the cerebral cortex without prior switching in the thalamus.[8] This direct access results from the phylogenetic age of the olfactory system – projections from the olfactory bulb reach directly the olfactory cortex (temporal lobe, the so-called primary olfactory/piriform cortex, and the adjacent entorhinal cortex) and structures of the limbic system. The limbic system comprises a group of interconnected structures deep in the brain responsible for emotions, memory, and autonomic responses. Key elements of the limbic system include the amygdala, hippocampus, and hypothalamus. Olfactory stimuli project directly to these areas: fibers leaving the olfactory bulb partially project to the amygdala (especially the corticomedial part of the amygdala) and to the hippocampal region (via the entorhinal cortex), as well as to the hypothalamus.[9]

These connections give scent a powerful influence on emotions and memories . The amygdala is responsible for assigning emotional meaning to stimuli and remembering emotionally charged events—it decides which information (received from the senses and cortex) to associate with the body's response (data from the hypothalamus and brainstem)[10][11]. The hippocampus participates in memory consolidation, including that related to the emotional context[12]. The hypothalamus, in turn, controls the secretion of stress hormones and autonomic responses (e.g., heart rate, blood pressure) via the sympathetic nervous system and pituitary gland[13]. Olfactory information reaching these structures therefore triggers immediate physiological responses: a pleasant scent can calm the amygdala and hypothalamus, promoting a feeling of calm, while an unpleasant scent can trigger anxiety or alarm. As Kandel and colleagues put it, "the emotional aspects of smell arise from limbic projections (amygdala and hypothalamus). Olfactory information is strongly linked to memory and emotion, which influences the stress response."[9] In other words, because of the direct connections between the olfactory nerve and the limbic system, odors can instantly activate our "emotion center" and modulate the body's stress response.

Mechanisms of the action of scents on the nervous and hormonal systems

Inhaling essential oils triggers a cascade of neural and neurochemical signals that modulate both the nervous and endocrine systems. Once the olfactory signal reaches the limbic system, neural circuits regulating the stress response are activated. The amygdala—a key structure for anxiety and fear—influences the hypothalamus, which initiates the HPA axis response. In stressful situations, the hypothalamus releases corticotropin-releasing hormone (CRH), stimulating the pituitary gland to secrete ACTH, which in turn stimulates the adrenal glands to secrete cortisol.

Pleasant olfactory stimuli may attenuate this response by inhibiting overactivation of the amygdala and facilitating a return to equilibrium. Indeed, stimulation of the olfactory system has been shown to influence hypothalamic and pituitary activity: aromas reaching the hypothalamus modulate the secretion of stress hormones and autonomic arousal[14]. Angelucci et al. (2014) reported that inhalation of olfactory stimuli triggers an immediate autonomic response—changes in blood pressure, heart rate, muscle tension, and brain activity—due to signals reaching the hypothalamus and limbic system[14]. Stimulation of the parasympathetic (vagal) branch of the autonomic nervous system results in a slower heart rate, vasodilation, and a feeling of relaxation, while inhibition of the overactive sympathetic nervous system reduces somatic symptoms of stress (e.g., palpitations, sweating).
At the level of the HPA axis , it has been shown that beneficial odors can reduce cortisol levels, the main stress hormone . Atsumi and Tonosaki (2007; PMID: 17337129) found that sniffing lavender and rosemary for just a few minutes increased the plasma's ability to neutralize free radicals and reduced the concentration of cortisol in the saliva of the subjects[15]. This confirms that olfactory signals can change the activity of the HPA axis in real time.

Similarly, Watanabe et al. (2015; PMID: 25824404) showed in a study involving 41 women that inhalation of bergamot oil for 15 minutes significantly reduced salivary cortisol levels compared to rest alone [16]. At the same time, an increase in vagal nerve activity was noted – the HF index in the heart rate variability (HRV) spectrum was higher after exposure to bergamot, which indicates an increase in parasympathetic tone and physiological relaxation [16].

The mechanisms of action of essential oils also include modulation of neurotransmitters in the brain. Aroma components can influence neurotransmitter systems associated with mood and anxiety , such as gamma-aminobutyric acid (GABA), serotonin (5-HT), and dopamine. For example, linalool—the main component of lavender —has shown in vitro affinity for glutamate receptors, which may explain its calming effect by suppressing neuronal hyperexcitability[17]. Other experiments suggest that lavender's anxiolytic mechanism depends on the serotonergic system: in animal models, antagonism of 5-HT1A receptors abolished the calming effects of lavender inhalation, suggesting serotonin's involvement in anxiety reduction[17]. Also the citrus component limonene (present e.g. in orange oil ) has an antidepressant effect – in experiments on mice, stress-induced hyperreactivity of the HPA axis and a decrease in the neurotrophic factor BDNF were abolished by exposure to the aroma of limonene[18][19].
Moreover, olfactory signals can trigger the release of neuromodulators associated with relaxation and well-being. Ogata et al. (2020; PMID: 32733584) observed in a pilot study that 20 minutes of lavender oil inhalation in healthy men reduced blood pressure and subjective tension, and an ex vivo study demonstrated that lavender activates oxytocin neurons in the hypothalamus[20]. Oxytocin, known as the "attachment hormone," has anxiolytic properties and lowers cortisol levels – this suggests that one of the mechanisms of aromatherapy may be the stimulation of oxytocin secretion in the brain, which secondarily calms the stress response [20].

In summary, scents act on multiple levels: through direct projections from the olfactory nerve to limbic centers, they influence emotions and autonomic responses, modulate the HPA axis by reducing hormonal markers of stress, and alter the balance of neurotransmitters in the brain (increasing the activity of inhibitory and "calming" systems such as GABAergic and serotonergic). This results in a reduction of stress symptoms—both subjective (feelings of anxiety, tension) and objective (heart rate, blood pressure, cortisol levels). The following sections present scientific evidence supporting these aromatherapy effects and describe oils with particularly potent anti-stress properties.

Research Review: Aromatherapy and Stress Reduction

Clinical trials (in humans)

A growing number of human studies confirm the effectiveness of aromatherapy in relieving stress and anxiety. These studies are conducted both in experimental settings with healthy volunteers and in clinical situations – for example, on patients before procedures, in hospitals, or during stressful everyday situations.
A classic field study was conducted by Lehrner et al. (2005; PMID: 16095639) in a dental office, examining the effect of scent on patient anxiety. Two hundred people awaiting dental procedures were exposed to the scent of either orange or lavender in the waiting room, and the results were compared with a control group (no scent) and a group exposed to relaxing music. They found that both the scent of orange and lavender significantly reduced patients' anxiety levels and improved their mood compared to the control group[21]. Those exposed to these pleasant scents felt calmer and more positive, demonstrating that passive inhalation of pleasant scents in a stressful environment reduces the stress response. Similar results were obtained by Kritsidima et al. (2010) in a randomized clinical trial: the scent of lavender in the waiting room reduced anxiety in dental patients compared to a placebo[22].

In experimental settings, physiological indicators of stress are often examined before and after essential oil inhalation. Chien et al. (2012; PMID: 21869900) conducted a 12-week study of 67 middle-aged women with insomnia, assessing the effects of lavender aromatherapy on the autonomic nervous system. The experimental group inhaled lavender oil for 20 minutes, twice a week. After just 4 weeks, a significant decrease in heart rate and an increase in high-frequency heart rate variability (HRV) were noted, indicating increased parasympathetic activity[23][24]. After 12 weeks, this effect persisted in the short term – immediately after lavender inhalation, parasympathetic dominance was greater than in the control group[25]. Furthermore, subjective sleep quality significantly improved in women receiving aromatherapy compared to controls[26]. This study shows that regular aromatherapy stimulates long-term beneficial autonomic adaptations, promoting relaxation and regeneration of the body.

Lavender is perhaps the most frequently studied oil for its anxiolytic effects. In addition to inhalation applications, there are also oral preparations containing its oil (e.g., Silexan capsules). In a multicenter, randomized clinical trial, Kasper et al. (2014; PMID: 24456909) demonstrated that lavender oil capsules (80–160 mg/day) administered for 10 weeks to patients with generalized anxiety disorder (GAD) significantly reduced anxiety severity (HAMA scale) compared to placebo, achieving effectiveness comparable to or even better than a standard anxiolytic drug (paroxetine)[27][28]. Importantly, lavender's anxiolytic effect occurred without the side effects typical of benzodiazepines or SSRIs. Although the oil was administered orally in this case, the results confirm the strong anxiolytic potential of Lavandula angustifolia – which correlates with observations from aromatherapy.

Very promising results also apply to citrus oils, especially bergamot. The aforementioned study by Watanabe et al. (2015) showed a significant reduction in cortisol and an increase in vagal nerve activity in healthy individuals after a short inhalation of bergamot oil[16]. Han et al. (2017) observed improved mood and increased energy levels in people in the waiting room of a mental health clinic where bergamot oil was diffused – just 15 minutes of exposure to this scent translated into higher ratings of mental well-being compared to the control group[29][30]. This group also reported lower levels of perceived stress and fatigue. Saiyudthong and Marsden (2011; PMID: 20669076) conducted a study on rats, showing that inhalation of bergamot oil reduced anxiety responses and lowered corticosterone levels (the equivalent of human cortisol) after acute stress on the animals – an effect similar to diazepam[31]. This confirms that bergamot has real anxiolytic properties, visible in both animals and humans.

Other clinical studies indicate the benefits of aromatherapy in various stressful situations. Hur et al. (2007) showed that intensive care unit nurses who regularly inhaled a mixture of oils (lavender, peppermint , rosemary ) had lower levels of perceived stress and lower cortisol concentrations than the control group[32][33]. Lee et al. (2011) reported improved heart rate variability and lower blood pressure in people undergoing a mental stress test after inhaling ylang-ylang oil compared to placebo[34][35]. Interesting results were also reported in EEG studies: Sayorwan et al. (2012) demonstrated that the scent of lavender increased the power of alpha and theta waves in the EEG, which is characteristic of relaxation and reduced arousal [36][37]. Thus, the subjective feeling of calm after lavender was reflected in objective measures of brain bioelectrical activity. In another experiment, Kuroda et al. (2005) found that the aroma of lavender in the procedure room reduced patients' anxiety before colonoscopy and reduced sympathetic nervous system activity as measured by hemodynamic parameters[38].

In summary, clinical studies suggest that aromatherapy demonstrates measurable stress- and anxiety-reducing effects in humans, as confirmed by a variety of methods: from psychological questionnaires and hormonal measurements (cortisol and adrenaline), to physiological parameters such as HRV, blood pressure, and EEG recordings. These effects have been observed in numerous populations: medical patients, healthy individuals under stress, workers under stress, and even children. Both the scent itself (its pleasantness and connotations) and the oil's chemical composition, which influences the nervous system, are important. The study results provide compelling evidence that inhaling appropriate essential oils alleviates subjective anxiety and objective markers of stress, thus promoting psychophysical well-being.

Experimental studies (mechanisms – animal models)

The mechanisms underlying aromatherapy are also being intensively studied in experimental animal models. This allows for insight into the neurophysiological effects of fragrances at the cellular and molecular levels, as well as the impact of isolated fragrance compounds. Overall, preclinical research consistently confirms the anti-stress effects of many essential oils and sheds light on their mechanisms.

Numerous experiments in rodents have shown that exposure to pleasant aromas reduces behavioral signs of anxiety and stress. For example, Goepfert et al. (2017) found that inhalation of vetiver oil in rats reduced anxiety responses in the elevated plus maze test, which was accompanied by reduced c-Fos expression in the central nucleus of the amygdala – suggesting inhibition of stress neuron activity in this structure[39][40]. Fukada et al. (2012) investigated the effects of rose oil on chronically stressed rats and found that inhalation of rose oil prevented many of the negative effects of stress (such as skin barrier damage and elevated corticosterone), likely through modulation of the HPA axis[41]. Another team demonstrated that the aroma of cypress (rich in so-called phytoncides, including α-pinene) alleviates the effects of early separation stress in rats – it reduced anxiety in behavioral tests and decreased the expression of proinflammatory cytokines (IL-6, CCL2, etc.) in the hippocampus of stressed young rats.[42][43] These results are consistent with the hypothesis that aromatherapy may suppress not only the HPA axis but also stress-related inflammatory processes in the brain, which is important in protecting the body from the damage of chronic stress.

Studies in mice often utilize standardized anxiety tests (plus maze, open field test, dark-light test). Li et al. (2018) examined the effects of ylang-ylang oil (Cananga odorata) in these models: both single and repeated exposure to its scent increased the time mice spent in the open arms of the maze and in the light part of the box – which clearly indicates an anxiolytic effect[44][45]. The authors identified three main components of ylang-ylang (benzylbenzoate, linalool, benzyl alcohol) responsible for this effect – administration of each of them separately also reduced anxiety in mice[46]. Importantly, changes in brain neurochemistry were also noted: in male mice, exposure to ylang-ylang decreased striatal dopamine levels and increased hippocampal serotonin levels[47], while also reducing the 5-HIAA/serotonin metabolite ratio, indicating enhanced serotonergic transmission. These neurotransmitter changes (↓DA, ↑5-HT) are typical of sedative and anxiolytic effects – and correspond to the effects observed in behavior. The authors' conclusions were clear: "both acute and chronic exposure to ylang-ylang oil exerts an anxiolytic effect, likely through its effects on serotonin and dopamine pathways"[48][49].

Many oils have also been tested for their effect on stress markers in the brain. The aforementioned α-pinene (a component of wood oils, e.g., pine and cypress ) not only improved the behavior of mice in anxiety tests but also increased the level of BDNF (a neurotrophic factor) in their hippocampus, which may indicate neuroprotective and antidepressant properties when exposed to this scent[50][51]. Komori et al., in turn, demonstrated in the 1990s that certain citrus scents (e.g., yuzu oil and lemonen) reduced the activity of the HPA axis in stressed rats, as measured by decreased ACTH and corticosterone levels in the blood and a reduction in stress-related stomach ulcers[52][29]. These results in experimental animals reinforce evidence from clinical studies – the effects of aromatherapy are not limited to subjective sensations but translate into measurable physiological changes, even at the level of genes and proteins in the brain (e.g., expression of c-Fos, BDNF, receptors, and cytokines). It is worth emphasizing that psychological factors (placebo effect, suggestion) can often be excluded in animal models, making the observed effects of fragrances even more biologically plausible.

Essential oils with the strongest anxiolytic effect

Not all scents are created equal – certain essential oils have been shown to have particular potential for relieving stress and anxiety, as confirmed by numerous studies. Below are some oils with documented anti-anxiety properties:

• Lavender (Lavandula angustifolia) – the "queen" of calming oils. Lavender oil has been traditionally used for years to induce calm and improve sleep, and modern research fully confirms its effectiveness. It contains high concentrations of linalool and linalyl acetate – compounds responsible for anxiolytic and sedative effects, including modulation of GABA_A and NMDA receptors.[53][54] Lavender inhalation reduces symptoms of anxiety in many situations: from pre-procedural stress, through anxiety states in psychiatric patients, to tension in healthy individuals under experimental conditions.[21][55] In a randomized clinical trial of dental patients, the scent of lavender reduced anxiety by ~20% on the STAI scale.[55] The oral preparation Silexan (80 mg of lavender oil) has been shown to be effective in the treatment of generalized anxiety disorder, reducing anxiety by over 14 HAMA points – a result better than placebo and comparable to paroxetine.[27][28] Lavender also improves physiological parameters: lowers blood pressure and heart rate, and increases heart rate variability (HRV), which indicates relaxation.[20][24]

Summary: Lavender is the most thoroughly studied anxiolytic oil with a multifaceted effect – it reduces subjective anxiety, stress axis reactivity (cortisol), calms the sympathetic nervous system, and facilitates relaxation . Example citations: Lehrner et al., 2005 (PMID: 16095639); Kasper et al., 2014 (PMID: 24456909).

• Bergamot (Citrus bergamia) – an oil obtained from the peel of the bergamot (citrus). It is characterized by a fresh, citrus aroma with mood-boosting properties. Studies show that bergamot acts quickly and effectively against stress. When inhaled, it causes a significant decrease in cortisol levels after just a few minutes of exposure[16], accompanied by a subjective improvement in mood (increased perceived energy, decreased tension)[29]. This oil increases parasympathetic activity (higher HF-HRV) and may lower blood pressure in stressful situations[16]. In animal experiments, bergamot reduced anxiety responses similarly to diazepam and limited stress-induced corticosterone increases[31]. The main components – limonene and linalool – are believed to be synergistic in this effect, influencing the limbic and endocrine systems. In clinical practice, the aroma of bergamot is sometimes used, for example, in hospital waiting rooms or therapy rooms to reduce tension in waiting patients.

Summary: Bergamot is an "anti-stress" citrus oil that has been shown in studies to reduce objective markers of stress (cortisol, heart rate) and improve well-being. Example citations: Watanabe et al., 2015 (PMID: 25824404); Saiyudthong & Marsden, 2011 (PMID: 20669076).

• Ylang-ylang (Cananga odorata) – an exotic floral oil with a sweet, balsamic scent. It is known for its pronounced calming and blood pressure-lowering effects. Hongratanaworakit and Buchbauer (2006; PMID: 16807875) demonstrated that the application of ylang-ylang oil causes a decrease in blood pressure and pulse rate while also increasing subjective feelings of calmness and relaxation.[56] In another study, inhalation of this oil reduced both systolic and diastolic blood pressure in healthy volunteers and slightly slowed reaction time (indicating a sedative effect).[34][35] Ylang-ylang may therefore reduce not only anxiety but also the physical symptoms of stress (hypertension, tension). At the neurochemical level, as mentioned, this scent modulates monoamine neurotransmission—increasing serotonin levels, decreasing dopamine, and through its linalool component, likely also affecting GABA receptors.[46][47] This promotes emotional calm. In aromatherapy, ylang-ylang is valued for soothing panic attacks, aiding sleep, and generally promoting a state of balance.

Summary: Ylang-ylang has a strong sedative effect, reduces blood pressure and tension , and induces a positive feeling of peace; however, it should be remembered that in excess it may cause excessive drowsiness or headache in sensitive individuals (due to its intense scent). Example citations: Hongratanaworakit & Buchbauer, 2006 (PMID: 16807875); Lee et al., 2011 (doi:10.1016/j.phymed.2011.02.005).

• Roman chamomile (Chamaemelum nobile) – an oil with a delicate, herbal-floral scent, known for its soothing properties. Although less researched than lavender, it has anti-anxiety properties – in one clinical study , aromatherapy massage with chamomile oil reduced anxiety levels and improved HRV in hospice patients.[57] Chamomile's components (e.g., apigenin) act on benzodiazepine receptors, among other things, explaining its calming effect. Chamomile is often used as a gentle remedy for nervous tension and insomnia.
• Frankincense (Boswellia) – a resinous oil with a warm, balsamic scent. Traditionally used in meditation and religious practices to calm the mind. In mice studies, the frankincense component, incensol acetate, demonstrated anxiolytic effects and activated TRPV3 channels in the brain, potentially promoting feelings of calm (Moussaieff et al., 2008). Inhalation of frankincense subjectively improves mood and reduces tension , although large clinical trials are lacking.
• Lemon balm (Melissa officinalis) – lemon balm leaf oil with a lemon-herbal aroma. Known for its anxiolytic and antidepressant properties, Hildegard of Bingen wrote that lemon balm "gladdens the heart." Modern lemon balm has been studied primarily in oral form (infusions, extracts), but its oil used aromatherapeutically also has a calming effect, reducing nervous arousal and promoting sleep. Koyama et al. (2016) report that lemon balm components act on GABA_A receptors similarly to diazepam, though less potently.

There are also other oils with calming properties, such as rosemary (although it stimulates the mind, it lowers cortisol levels when combined with lavender[15]), neroli (bitter orange flower oil, used for insomnia and anxiety), nutmeg sage, jasmine (acts more like an antidepressant), sandalwood (calming, used in clinical aromatherapy to relieve anxiety).

In aromatherapy practice, mixtures of several oils are often used to achieve a synergistic effect.

However, among them, lavender, bergamot, and ylang-ylang are most often cited as the first choice in stress therapy due to their strong and repeatedly confirmed effects. In aromatherapy, blends of several oils are often used to achieve a synergistic effect – for example, lavender + bergamot + ylang-ylang constitute a composition with powerful relaxing potential (such a blend, with the addition of marjoram and neroli, lowered blood pressure in patients with hypertension[29][30]).

The individual selection of the fragrance is also crucial – the scent must be pleasant for a specific person.

The individual selection of the scent is also crucial – the scent must be pleasant for a specific person to evoke a positive emotional reaction, as emphasized by aromatherapists[11][58].

Conclusions - A Scientific Look at the Effects of Aromatherapy on Stress

The scientific evidence gathered clearly indicates that aromatherapy can be an effective tool in reducing stress and anxiety, acting through the unique olfactory nerve pathway directly to the "emotional brain."

The biological basis of this phenomenon includes the rapid stimulation of the limbic system and hypothalamus by odor molecules, which leads to modulation of the stress response – a reduction in HPA axis activity (reduced cortisol and adrenaline secretion) and activation of the parasympathetic nervous system (relaxation, homeostasis). Mechanisms at the level of neurotransmitters (GABA, 5-HT, dopamine, oxytocin) additionally contribute to mental and physical calm. The results of numerous clinical studies – from pilot studies to randomized controlled trials – confirm that carefully selected essential oils reduce the perception of stress, anxiety, and related somatic symptoms (e.g., tachycardia, hypertension).

Experimental studies on animal models lend credence to these observations, showing tangible changes in the brain and body under the influence of odors (including in the expression of stress genes, hormone concentrations, and the activity of limbic neurons).
It's important to emphasize that while aromatherapy holds promise, further research is needed to fully understand its effectiveness and mechanisms. Much of the research to date is short-term; large, long-term studies assessing the impact of regular aromatherapy on health in chronic stress are lacking.

Standardization of protocols (e.g., inhalation dose and duration, diffusion method) and comparisons between different oils and their active ingredients are necessary. Another interesting direction is to explore the personalization of aromatherapy – not every scent has the same effect on everyone, therefore individual preferences and scent associations can modulate the therapeutic effect[11].

The current state of knowledge justifies the integration of aromatherapy as a supportive method in stress management, especially chronic stress.

Despite these challenges, the current state of knowledge justifies the integration of aromatherapy as a supportive method in stress management, especially chronic stress. It can serve as a valuable complementary element alongside conventional methods (psychotherapy, pharmacotherapy) or relaxation techniques. Its advantages include simplicity, naturalness, and minimal invasiveness – when used appropriately, aromatherapy is safe and well-tolerated, while also having a holistic effect on the mind and body.

With the increasing incidence of stress-related disorders (such as anxiety, insomnia, and depression), it's worth conducting further research and developing aromatherapy protocols with proven effectiveness. However, the available data already suggests that scent can be a powerful ally in the fight against the "silent killer" – stress , helping to restore the body's neurohormonal balance and improve the quality of life for people exposed to chronic stress[59][60].

A fresh look at the age-old wisdom of aromas suggests that perhaps a return to "aroma therapy" – used instinctively since antiquity – will find a permanent place in modern medicine as a valuable complement to standard methods of coping with stress.

Sources: Studies and articles cited in the text (e.g., Masuo et al., 2021[9][29]; Kasper et al., 2014[27]; Lehrner et al., 2005[21]; Watanabe et al., 2015[16]; Hongratanaworakit, 2006[56]; and others cited in citations). All cited works are available through PubMed/PMC (PMID provided where possible) or in the specialized literature. They confirmed the facts presented in this article.

[1] [2] [5] [6] [9] [15] [18] [19] [29] [30] [31] [32] [33] [39] [40] [41] [42] [43] [50] [51] [52] [59] [60] Smell and Stress Response in the Brain: Review of the Connection between Chemistry and Neuropharmacology
https://www.mdpi.com/1420-3049/26/9/2571
[3] [4] [7] [10] [11] [12] [13] [57] [58] Emotional aromatherapy, or how essential oils influence our emotions - Ziołowe Zacisze
https://ziolowezacisze.pl/aromaterapia-emocjonalna-czyli-jak-olejki-eteryczne-wplywaya-na-nasze-emocje/
[8] Biomedicine 1 - Sense Organs: Vision, Smell, Taste and the Nervous System - Studocu
https://www.studocu.com/pl/document/spoleczna-akademia-nauk-w-lodzi/biologiczne-podstawy-zachowania/zagadnienia-biomedyka-1/84284431
[14] The Effects of Essential Oils on the Nervous System: A Scoping Review | MDPI
https://www.mdpi.com/1420-3049/28/9/3771
[16] Effects of bergamot (Citrus bergamia (Risso) Wright & Arn.) essential oil aromatherapy on mood states, parasympathetic nervous system activity, and salivary cortisol levels in 41 healthy females - PubMed
https://pubmed.ncbi.nlm.nih.gov/25824404/
[17] [44] [45] [46] [47] [48] [49] [53] [54] The anxiolytic effect of essential oil of Cananga odorata exposure on mice and determination of its major active constituents - ScienceDirect
https://www.sciencedirect.com/science/article/abs/pii/S0944711316301908
[20] Lavender Oil Reduces Depressive Mood in Healthy Individuals and Enhances the Activity of Single Oxytocin Neurons of the Hypothalamus Isolated from Mice: A Preliminary Study - PubMed
https://pubmed.ncbi.nlm.nih.gov/32733584/
[21] Ambient odors of orange and lavender reduce anxiety and improve mood in a dental office - PubMed
https://pubmed.ncbi.nlm.nih.gov/16095639/
[22] [38] Effects of Pleasant Ambient Fragrances on Dental Fear
https://pmc.ncbi.nlm.nih.gov/articles/PMC2975911/
[23] [24] [25] [26] [55] The Effect of Lavender Aromatherapy on Autonomic Nervous System in Midlife Women with Insomnia - PMC
https://pmc.ncbi.nlm.nih.gov/articles/PMC3159017/
[27] [28] Lavender oil preparation Silexan is effective in generalized anxiety disorder--a randomized, double-blind comparison to placebo and paroxetine - PubMed
https://pubmed.ncbi.nlm.nih.gov/24456909/
[34] Learn the Amazing Health Benefits of Ylang Ylang Oil
https://achs.edu/blog/practical-wonders-of-ylang-ylang-oil/
[35] Effects of Ylang-Ylang aroma on blood pressure and heart rate in ...
https://www.researchgate.net/publication/258925284_Effects_of_Ylang-Ylang_aroma_on_blood_pressure_and_heart_rate_in_healthy_men
[36] [37] Frontiers | Scents modulate anxiety levels, but electroencephalographic and electrocardiographic assessments could diverge from subjective reports: a pilot study
https://www.frontiersin.org/journals/behavioral-neuroscience/articles/10.3389/fnbeh.2025.1534716/full
[56] Relaxing effect of ylang ylang oil on humans after transdermal absorption - PubMed
https://pubmed.ncbi.nlm.nih.gov/16807875/