Abstract
BackgroundPrevious studies suggested that essential oils suppressed the adherence response of human neutrophils in vitro and that intraperitoneal application of geranium oil suppressed the neutrophil accumulation into peritoneal cavity in vivo. Usually, essential oils are applied through skin in aromatherapy in inflammatory symptoms. The purpose of this study is to assess the effects of cutaneous application of essential oils on the accumulation of neutrophils in inflammatory sites in skin of mice.MethodsInflammation with accumulation of inflammatory cells was induced by injection of curdlan, a (1→3)-β-D-glucan in skin or peritoneal cavity of mice. Essential oils were applied cutaneously to the mice immediately and 3 hr after intradermal injection of curdlan. The skin with inflammatory lesion was cut off 6 hr after injection of curdlan, and the homogenates were used for myeloperoxidase (MPO: a marker enzyme of neutrophil granule) assay.ResultsThe MPO activity of the skin lesion induced by curdlan was suppressed dose-dependently by cutaneous application of geranium oil. Other oils such as lavender, eucalyptus and tea tree oils also suppressed the activity, but their activities seemed weaker than geranium. Juniper oil didn't suppress the activityConclusionCutaneous application of essential oils, especially geranium oil, can suppress the inflammatory symptoms with neutrophil accumulation and edema.
Highlights
Previous studies suggested that essential oils suppressed the adherence response of human neutrophils in vitro and that intraperitoneal application of geranium oil suppressed the neutrophil accumulation into peritoneal cavity in vivo
We reported that the essential oils: lemongrass, geranium and spearmint suppressed the adherence response of human neutrophils in vitro [10], and that the intraperitoneal administration of geranium oil to mice lowered neutrophil recruitment into the peritoneal cavity induced by a chemotactic agent, casein injection in vivo [9]
The MPO value and skin weight of the skin lesion 6 hr after curdlan injection were 4.54 ± 2.43 units/skin lesion and 22.5 ± 8.3 mg (n = 49), which were significantly higher than those of saline injection, 0.21 ± 0.14 units/skin lesion and 8.9 ± 1.4 mg, respectively (n = 4). This indicates that curdlan injection caused neutrophil accumulation, which was monitored by increase in the MPO activity, and skin edema, which was observed by increase in skin weight
Summary
Previous studies suggested that essential oils suppressed the adherence response of human neutrophils in vitro and that intraperitoneal application of geranium oil suppressed the neutrophil accumulation into peritoneal cavity in vivo. The purpose of this study is to assess the effects of cutaneous application of essential oils on the accumulation of neutrophils in inflammatory sites in skin of mice. The clinical use of essential oils has expanded worldwide to include therapy against various kinds of inflammatory diseases, such as allergy, rheumatism and arthritis. These activities have mainly been recognized through clinical experience, especially through skin application via massage and ointment, but there have been relatively little scientific study on their biological actions. Several investigators have suggested that tea tree [1,2] and lavender oils [3] suppressed allergic symptoms through (page number not for citation purposes).
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