We report the case of a 4-year-old boy who presented with a transient extensive eczematous eruption on the left side of his trunk and extremities, with clear demarcation in the midline. The eruption started to resolve without any sequelae in 4 weeks. The history and clinical findings suggest that this transient eruption could have been either a case of unilateral blaschkitis in childhood or asymmetric periflexural exanthem.