Anti-Inflammatory Action of Geranium Essential Oil
Suppression of Carrageenan- and Collagen II-Induced Inflammation in Mice by Geranium Oil
Authors: Naho Maruyama, Hiroko Ishibashi, Weimin Hu, Shinichiro Morofuji, Shigeharu Inouye, Hideyo Yamaguchi, and Shigeru Abe
To obtain experimental evidence on the therapeutic efficacy of essential oils in aromatherapy for inflammatory diseases, we examined the effects of geranium oil on carrageenan-induced and collagen II-induced inflammation in mice, to assess acute and chronic anti-inflammatory activities of the oil. Single intraperitoneal injection of 5 ?L of geranium oil clearly suppressed the carrageenan-induced footpaw edema and increase in tissue myeloperoxidase activity, and repeated administration of the oil suppressed collagen-induced arthritis. These results revealed that geranium oil suppressed both acute and chronic inflammatory responses in mice.
Aromatherapy is one of the alternative medicines using essential oils and has long been used as an herbal medicine. Recently essential oils have been empirically used worldwide for clinical conditions including various kinds of inflammatory diseases, such as allergy, rheumatism, and arthritis. These activities have mainly been recognized through clinical experience, but there has been relatively little evidence about the pharmacological actions of these oils.
Several investigators have suggested that tea tree [1, 2] and lavender  oils suppressed allergic symptoms through the suppression of histamine release [4, 5] and cytokine production  in vitro and in vivo. Several essential oils such as eucalyptus  and lavender  oils inhibited carrageenan-induced paw edema. Moreover, in human, skin application of tea tree oil was reported to suppress the edema induced by intradermal injection of histamine . However, the chronic effects of essential oils using inflammatory mice model have hardly been investigated.
Previously we reported that the essential oils such as geranium oil suppressed the adherence response of neutrophils in vitro , and that the intraperitoneal administration of geranium oil lowered neutrophil recruitment into the peritoneal cavity induced by injection of a chemotactic agent, casein in vivo . We also reported that both intraperitoneal and cutaneous applications of the oil suppressed cellular inflammation and neutrophil accumulation to the inflammatory sites which were induced by curdlan, a linear (1 ? 3)-?-D-glucan known as an immunostimulating substance in fungi . These results suggested the possibility that geranium oil might effectively suppress symptoms in inflammatory disease associated with neutrophil activities.
In the present study, we investigated the effects of geranium oil on carrageenan-induced foot edema and collagen-induced arthritis, which are models for acute and chronic inflammation accompanied by neutrophil accumulation.
It was noted that 5 ?L of geranium oil suppressed the foot swelling during and after the oil injection period, suggesting a long-lasting effect of this oil. Preliminary study showed that indomethacin inhibited the swelling only during its administration, and 1 week after completion of the injection the feet gradually swelled (data not shown). This indicates that repetitive administration of the oil may elicit a long-lasting effect.
In aromatherapy, several essential oils can be applied as a help in therapeutic treatments for inflammatory symptoms with lesional neutrophil accumulation, such as arthritis, aphthous stomatitis, lesional bacterial or fungal infections. Their effectiveness is postulated clinically, but little experimental evidence has been obtained. Our two results give basic evidence about the activity of geranium oil for both acute and chronic inflammatory disorders.
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