Uterotrophic assay of percutaneous lavender oil in immature female rats

Critical assessment of the endocrine potential of Linalool and Linalyl acetate: proactive testing strategy assessing estrogenic and androgenic activity of Lavender oil main components

The acyclic linear monoterpenes Linalool (Lin) and Linalyl acetate (LinAc) occur in nature as major constituents of various essential oils such as lavender oils. A potential endocrine activity of these compounds was discussed in literature including premature thelarche and prepubertal gynecomastia due to lavender product use. This study aims to follow-up on these critical findings reported by testing Lin and LinAc in several studies in line with current guidance and regulatory framework. No relevant anti-/ER and AR-mediated activity was observed in recombinant yeast cell-based screening tests and guideline reporter gene in vitro assays in mammalian cells. Findings in the screening test suggested an anti-androgenic activity, which could not be confirmed in the respective mammalian cell guideline assay. Mechanistic guideline in vivo studies (Uterotrophic and Hershberger assays) with Lin did not show significant dose related changes in estrogen or androgen sensitive organ weights and a guideline reproductive toxicity screening study did not reveal evident effects on sex steroid hormone sensitive organ weights, associated histopathological findings and altered sperm parameters. Estrous cycling and mating/fertility indices were not affected and no evident Lin-related steroid hormone dependent effects were found in the offspring. Overall, the initial concerns from literature were not confirmed. Findings in the yeast screening test were aberrant from follow-up guideline in vitro and in vivo studies, which underlines the need to apply careful interpretation of single in vitro test results to support a respective line of evidence and to establish a biologically plausible link to an adverse outcome.

Are Prepubertal Gynaecomastia and Premature Thelarche Linked to Topical Lavender and Tea Tree Oil Use?

Various studies, conducted since 2007, have reported a total of eight boys with prepubertal gynaecomastia and four girls with premature thelarche following exposure to lavender and/or tree tea oil. All patients experienced regression of the breast tissue after they stopped using these oils. Both of these essential oils, and several of their constituents, have oestrogenic and antiandrogenic activity in vitro. However, limited dermal penetration of some of the components means that the in vitro findings cannot be extrapolated to the in vivo situation. There are unanswered questions as to how much lavender or tea tree oil was actually present in the skincare products used by the children and a lack of information about exposure to other agents. Furthermore, since both prepubertal gynaecomastia and premature thelarche often spontaneously regress, it cannot be concluded that the use of lavender and/or tree tea oil is the cause of the gynaecomastia and thelarche in these children.

Comparative Studies on the Anti-Inflammatory and Apoptotic Activities of Four Greek Essential Oils: Involvement in the Regulation of NF-κΒ and Steroid Receptor Signaling

Essential oils (EOs) are well-known for their anti-fungal, anti-microbial, anti-inflammatory and relaxing activities. Steroid hormones, especially glucocorticoids, are also well-known for their anti-inflammatory activities and control of the hypothalamus-pituitary-adrenal (HPA) axis and glucose homeostasis. The biological activities of glucocorticoids render them the most widely prescribed anti-inflammatory drugs, despite their adverse side effects. In this study, comparative studies of the anti-inflammatory activities and interference with glucocorticoids receptor (GR) and estrogen receptor (ER) signaling of EOs from Greek Oregano, Melissa officinalis, Lavender and from the Chios Mastic, produced from the Greek endemic mastic tree, were performed in Human Embryonic Kidney 293 (HEK-293) cells. Chios Mastic (Mastiha) and oregano EOs exhibited the highest anti-inflammatory activities. The former showed a reduction in both NF-κB activity and protein levels. Mastic essential oil also caused a reduction in GR protein levels that may compensate for its boosting effect on dexamethasone (DEX)-induced GR transcriptional activation, ending up in no induction of the gluconeogenic phoshoenolpyruvate carboxykinase (PEPCK) protein levels that constitute the GR target. Oregano, Melissa officinalis and lavender EOs caused the suppression of the transcriptional activation of GR. Furthermore, the most active EO, that taken from Melissa officinalis, showed a reduction in both GR and PEPCK protein levels. Thus, the anti-inflammatory and anti-gluconeogenic activities of the EOs were uncovered, possibly via the regulation of GR signaling. Moreover, cytotoxic actions of Melissa officinalis and lavender EOs via the induction of mitochondrial-dependent apoptosis were revealed. Our results highlight these essentials oils' anti-inflammatory and apoptotic actions in relation to their implication on the regulation of steroid hormones' actions, uncovering their potential use in steroid therapy, with many applications in pharmaceutical and health industries as anti-cancer, anti-hyperglycemic and anti-inflammatory supplements.

Prevalence of endocrine disorders among children exposed to Lavender Essential Oil and Tea Tree Essential Oils

Background

Lavender essential oil and tea tree essential oil have become popular ingredients in personal care and household products in recent decades. Questions regarding the safety of these oils in pediatric populations have been raised, proposing a link between these essential oils and endocrine disruption in children, specifically prepubertal gynecomastia. To date, no epidemiological studies have been conducted to evaluate this proposed link.

Methods

This is a cross sectional study conducted among parents of children in the United States to identify the prevalence of endocrine disruption in children aged 2-15 years old. This study also evaluates the potential for a relationship between the exposure of lavender essential oil and tea tree essential oil products and endocrine disrupting outcomes.

Results

In 556 children with a mean age of 6.33 (SD = 3.92), prevalence of endocrine disruption was .016 (SD = 0.13). No cases of prepubertal gynecomastia were identified in either group, and prevalence of precocious puberty, delayed puberty, growth hormone deficiency, and hypothyroidism were all consistent with population norms. Total risk of endocrine disorders among those exposed (0.0194) did not differ from the risk of those unexposed (0.0069). The risk ratio was 2.796 (95% CI: 0.352, 22.163, P = .458).

Conclusion

Children who were regularly exposed to lavender or tea tree essential oils experienced the same risk of endocrine disorders as those who were not exposed.

Association of Early Pubertal Onset in Female Rats With Inhalation of Lavender Oil

BACKGROUND

Central precocious puberty (CPP) is caused by early activation of the hypothalamic-pituitary-gonadal axis but its major cause remains unclear. Studies have indicated an association between chronic environmental exposure to endocrine-disrupting chemicals and pubertal onset. Essential oil is widely used in homes worldwide for relief of respiratory symptoms, stress, and/or sleep disturbance.

METHODS

To evaluate this association, we compared the hormone levels and timing of vaginal opening (VO) in female rats exposed to lavender oil (LO) through different routes (study groups: control, LO nasal spray [LS], and indoor exposure to LO [LE]) during the prepubertal period. The body weights of the animals were also compared every 3 days until the day of VO, at which time gonadotropin levels and internal organ weights were assessed.

RESULTS

The LS group showed early VO at 33.8 ± 1.8 days compared with the control (38.4 ± 2.9 days) and LE (36.6 ± 1.5 days) groups. Additionally, luteinizing hormone levels were significantly higher in the LE and LS groups than those in the control group. Body weights did not differ significantly among the groups.

CONCLUSION

Inhalation exposure to an exogenic simulant during the prepubertal period might trigger early pubertal onset in female rats. Further evaluation of exposure to other endocrine-disrupting chemicals capable of inducing CPP through the skin, orally, and/or nasally is warranted.

The relationship between lavender and tea tree essential oils and pediatric endocrine disorders: A systematic review of the literature

OBJECTIVES

Essential oils are common ingredients in personal care products, little is known about the effects of chronic exposure to these ingredients in human health. It has been suggested that these two essential oils cause prepubertal gynecomastia and premature thelarche in children. The purpose of this study was to systematically review the evidence related to the proposed link between these essential oils and endocrine disruption METHODS: This study sought to investigate the proposed link between LEO and TTEO and endocrine disrupting outcomes by identifying and evaluating the clinical evidence regarding this topic. Studies qualified if the participants included prepubertal children who have experienced either prepubertal gynecomastia or premature thelarche. The Case Series Critical Appraisal Tool (CSCAT) was used to identify the reliability of the identified case series. The potential for evidence of causality was evaluated using the tool proposed by Murad.

RESULTS

A total of four manuscripts were identified, describing a total of eleven cases reported to have experienced both the exposure and the outcome. Reporting of inclusion, demographic data, clinical data, and the potential for causality was found to be insufficient. This study did not find evidence to support the claim that tea tree essential oil is related to endocrine disruption in children, and little to no evidence to substantiate the proposed link between lavender essential oil and endocrine disruption in children.

CONCLUSION

Because this potential link remains a concern among pediatric care providers and parents, epidemiological research to address the proposed link is needed.

Lavender Products Associated With Premature Thelarche and Prepubertal Gynecomastia: Case Reports and Endocrine-Disrupting Chemical Activities

CONTEXT

Previous case reports associated prepubertal gynecomastia with lavender-containing fragrances, but there appear to be no reports of premature thelarche.

OBJECTIVE

To add to a case series about lavender-fragranced product use and breast growth in children and to measure endocrine-disrupting chemical activity of essential oil components.

DESIGN, SETTING, AND PATIENTS

Patients experiencing premature thelarche or prepubertal gynecomastia with continuous exposure to lavender-fragranced products were evaluated in the pediatric endocrinology departments of two institutions. Mechanistic in vitro experiments using eight components of lavender and other essential oils were performed at National Institute of Environmental Health Sciences.

MAIN OUTCOME MEASURES

Case reports and in vitro estrogen and androgen receptor gene expression activities in human cell lines with essential oils.

RESULTS

Three prepubertal girls and one boy with clinical evidence of estrogenic action and a history of continuous exposure to lavender-containing fragrances were studied. Breast growth dissipated in all patients with discontinuation of the fragranced products. Some of the components tested elicited estrogenic and antiandrogenic properties of varying degrees.

CONCLUSION

We report cases of premature thelarche that resolved upon cessation of lavender-containing fragrance exposure commonly used in Hispanic communities. The precise developmental basis for such conditions could be multifactorial. In vitro demonstration of estrogenic and antiandrogenic properties of essential oil components suggests essential oils in these cases could be considered a possible source and supports a possible link with idiopathic prepubertal breast development. Whether the level of lavender oil estrogenic potency is sufficient to cause these effects is unknown.

Soy Isoflavone Protects Myocardial Ischemia/Reperfusion Injury through Increasing Endothelial Nitric Oxide Synthase and Decreasing Oxidative Stress in Ovariectomized Rats

There is a special role for estrogens in preventing and curing cardiovascular disease in women. Soy isoflavone (SI), a soy-derived phytoestrogen, has similar chemical structure to endogenous estrogen-estradiol. We investigate to elucidate the protective mechanism of SI on myocardial ischemia/reperfusion (MI/R) injury. Female SD rats underwent bilateral ovariectomy. One week later, rats were randomly divided into several groups, sham ovariectomy (control group), ovariectomy with MI/R, or ovariectomy with sham MI/R. Other ovariectomy rats were given different doses of SI or 17β-estradiol (E2). Four weeks later, they were exposed to 30 minutes of left coronary artery occlusion followed by 6 or 24 hours of reperfusion. SI administration significantly reduced myocardial infarct size and improved left ventricle function and restored endothelium-dependent relaxation function of thoracic aortas after MI/R in ovariectomized rats. SI also decreased serum creatine kinase and lactate dehydrogenase activity, reduced plasma malonaldehyde, and attenuated oxidative stress in the myocardium. Meanwhile, SI increased phosphatidylinositol 3 kinase (PI3K)/Akt/endothelial nitric oxide synthase (eNOS) signal pathway. SI failed to decrease infarct size of hearts with I/R in ovariectomized rats if PI3K was inhibited. Overall, these results indicated that SI protects myocardial ischemia/reperfusion injury in ovariectomized rats through increasing PI3K/Akt/eNOS signal pathway and decreasing oxidative stress.