Anti-allergic rhinitis activity of tea tree (Melaleuca alternifolia) essential oil in mice sensitized and challenged with Japanese cedar pollen

Abstract

Effects of tea tree (TT) essential oil on allergic rhinitis (AR) induced by Japanese cedar pollen (JCP) were investigated. Mice were sensitized by i.p. injections with JCP+alum on days 0, 7 and 14. From day 21, the sensitized mice were challenged by intranasal (i.n.) administrations of JCP for 4 consecutive days. Animals were also treated with TT (i.n.) 30 min before each JCP challenge. Frequency of sneezing was counted for 20 min after each nasal challenge. On days 18 and 25, the histamine (Hist, i.n.)-induced sneezing was also counted. In mice that were sensitized and repeatedly challenged with JCP, both serum levels of IgG and IgE specific for Cry J1, a major allergen of JCP, were significantly increased: the TT treatments did not affect the increase in Cry J1-specific antibodies. In the JCP-sensitized mice, JCP challenge caused a significant increase in sneezing, indicating that nasal allergic response was induced. The i.n. application of Hist also caused an increase in sneezing. The Hist-induced sneezing was further increased significantly on day 25, indicating that nasal hyperresponsiveness (NHR) had occurred after the repeated JCP challenges. Both the nasal allergic response and NHR induced by JCP were inhibited by the pretreatments with TT. Thus, TT might be useful for the treatment of AR induced by JCP.