  We first construct the effective chiral Lagrangians for the $1^{-+}$ exotic
mesons. With the infrared regularization scheme, we derive the one-loop
infrared singular chiral corrections to the $\pi_1(1600)$ mass explicitly. We
investigate the variation of the different chiral corrections with the pion
mass under two schemes. Hopefully, the explicit non-analytical chiral
structures will be helpful to the chiral extrapolation of the lattice data from
the dynamical lattice QCD simulation of either the exotic light hybrid meson or
tetraquark state.
