Abstract: OBJECTIVE To study the effect of pseudoallergic reactions of Qingkailing injections and its mechanisms. METHODS The BALB/c mice and BN rats were used to observe the changes of vascular permeability, mean arterial blood pressure(MABP) and other pseudoallergic reactions indicators with Qingkailing injection. RBL-2H3 cells were stimulated with Qingkailing injections and then were used to observe the activity of PI3K and the protein expression of Rac1, Pak1, Limk1 and cofilin. RESULTS The 5 mL·kg^-1 Qingkailing injection could cause to vascular permeability increase in mice as the main performance of the pseudoallergic reactions, while 7.5 mL·kg^-1 and 15 mL·kg^-1 Qingkailing injection caused serious pseudoallergic reactions in mice. Qingkailing injection in 5, 7.5 and 15 mL·kg^-1 caused rats' MABP to reduce in a dose dependent manner. In vitro, Qingkailing injection can induce pseudoallergic reactions and increase in levels of PI3K, Rac1, PAK1, LIMK1 and cofilin in a dose dependent manner in RBL-2H3 cells. CONCLUSION The tests in mice, rats and the content test of PI3K kinase, Rac1, PAK1, LIMK1 and cofilin in RBL-2H3 cells can be used as kinds of pseudoallergic reactions tests. Pseudoallergic reactions induced by Qingkailing injection is likely to be based on PI3K-Rac1 signal transduction pathways.