Correcting Overlapping and Underlapping Toes. Overlapping and underlapping toes are deformities seen when one or more of the toes lies on top of or underneath other toes. Other deformities such as bunions or hammertoes may be present at the same time, and bunions may actually cause toes to overlap. Pressure from the toe box often causes hard corns to develop. Also, soft corns and blisters are apt to develop where the toes rub on each other. The toes themselves generally do not hurt, but the corns and blisters can be very painful. Overlapping toes usually affects the fifth toe and it can occur prior to birth.