We study the net chirality in the s pin helix structure of Ho/Y multilayers induced by an in-plane applied magnetic field. The lifting of degeneracy of the chiral symmetry was revealed by means of polarized neutron reflectometry. Three samples of different thicknesses of t he Ho and Y layers were grown by molecular-beam epitaxy. The chiral states are degenerated upon zero field cooling below the critical temperature TN = 115 ± 3K.The chirality parameter γ rises during the field cooling procedure in the field range from 0 to 1 T and saturates at a value of 0.12 ± 0.01. The chirality appears stepwise below TN and depends weakly on temperature. T he phenomenon is interpreted in terms of the Dzyaloshinskii-Moriya interaction appearing at t he interface between the Ho and Y layers.