Eucalyptus oil reduces allergic reactions and suppresses mast cell degranulation by downregulating IgE-FcεRI signalling

Eucalyptus oil has traditionally been used for bactericidal, anti-inflammatory, analgesic, and sedative effects. Building on reports that it suppresses chemokines, cytokines, and lipid mediators in immune cells, this study tested whether Eucalyptus oil can be used for allergic dermatitis using a mouse IgE-mediated local allergic model. Topical Eucalyptus oil suppressed edema and vascular hyperpermeability in IgE-mediated skin reactions. Mast cell degranulation was inhibited, and the main component 1,8-cineole was examined for effects on signalling. 1,8-cineole suppressed mast cell degranulation and inhibited phosphorylation of PLCγ and p38, indicating it acts directly or indirectly on IgE–FcεRI downstream signalling to reduce allergic responses.