The alterations in the localization of keratinocyte membrane glycoconjugates in allergic contact dermatitis were investigated in guinea pig skin treated with topical application of 2.4-dinitro-chlorobenzene. We employed the avidin-biotin complex(ABC) method for the detection of localization of 10 commercially available lectins labelled with biotin: Con-A, SBA, WGA, DBA, UEA-1, RCA-1, PNA, HP, MPA, and ECA. Staining with WGA showed a remarkably decreased intensity in basal and spinous layers of the allergic skin in comparison to those of the control skin, suggesting loss of terminal sialic acids in cell membrane glycoconjugates. The other lectins showed no remarkable difference in the staining patterns between the normal and the allergic ski. The results suggest that epidermal cell membrane glycoconjugates undergoes selective perturbations in acute allergic contact dermatitis, and that the keratinocytes might be an active part of the cutaneous immune system.