Lavender and several of its constituents have been tested for pharmacological activity.
The sedative properties of the essential oil and its main constituents (linalool and linalyl acetate) were shown to have a dose-dependent effect in mice and to reverse caffeine-induced hyperactivity in mice, as well as reduce stress, as indicated by modulation of ACTH, catecholamine and gonadotropin levels in experimental menopausal rats, and reduce cortisol responses in infant Japanese macaques. Inhalation of lavender has also been shown to produce a dose-dependent anticonvulsant effect in both rats and mice.
In human trials, inhalation of lavender has been shown to induce relaxation and sedation and to alter EEG responses, as well as significantly decreasing heart rate and increasing high-frequency spectral components to produce calm and vigorous mood states in healthy volunteers. Transdermal absorption of linalool without inhalation produced a decrease in systolic blood pressure and a smaller decrease of skin temperature with no effects on subjective evaluation of wellbeing in healthy human subjects, and another study found that lavender scent was associated with lower fatigue following an anxiety-provoking task.
These positive studies are contrasted by studies with negative findings. Lavender aromatherapy did not significantly improve scores on the Hospital Anxiety and Depression Scale or the Somatic and Psychological Health Report (SPHERE) in a RCT of 313 patients undergoing radiotherapy and a study of 169 subjects, including both depressed and non-depressed subjects, showed lavender increased fatigue, tension, confusion, and total mood disturbance, and decreased vigour.
Various in vitro data suggest that lavender oil has antibacterial, antifungal and mitocidal activities, with both lavender and linalool having fungistatic and fungicidal activity against Candida albicans strains at high concentrations and inhibiting germ tube formation and hyphal elongation at low concentrations, suggesting it may be useful for reducing fungal progression and the spread of infection in host tissues. Lavender has been shown to be active alone and to work synergistically with tea tree oil against the fungi responsible for tinea and onychomycosis.
The fungistatic properties of linalool have led to the suggestion that it could be used to complement environmental measures in preventing fungal contamination in storage areas of libraries.
Linalool, one of lavender’s major components, demonstrated spasmolytic activity when tested on an in vitro preparation of guinea-pig ileum smooth muscle.
In vitro and animal studies suggest that perillyl alcohol and D-limonene (see Clinical note) may have useful chemotherapeutic and chemoprotective effects in a range of cancers, including cancer of the colon, liver, lung, breast, pancreas and prostate, as well as in melanoma. These results have not yet been confirmed in human studies.
Lavender: Other Actions
When applied topically, lavender oil has rubefacient properties and is thought to have analgesic, antihistaminic and anti-inflammatory activities. A small study comparing the effects of a bath containing lavender oil, synthetic lavender oil, and distilled water in reducing perineal discomfort after childbirth found lower mean discomfort scores in the lavender group; however, the differences between groups were not significant.
Traditionally, lavender oil is considered to have a balancing effect on the CNS, acting as an aromatic stimulant or calming agent.
Extracts of Lavandula multifida have been found to have topical anti-inflammatory activity in mice, with some extracted compounds having activity comparable to that of indomethacin. At high concentrations (0.1%) lavender oil has also been found to suppress TNF-alpha-induced neutrophil adherence. Lavender has also demonstrated powerful anti-oxidant activity, as well as antimutagenic activity and antiplatelet and antithrombotic properties demonstrated both in vitro and in vivo.