Hands are washed in preparation to the handling of food. The Talmud states that when a food is dipped in liquid, hands are to be washed first as a sign of ritual purity (Pesahim 115a). There are different customs regarding who should wash their hands before partaking of the greens. In some homes the person conducting the Seder washes before handing out the greens while in other homes all the participants wash their hands before handling the greens. In the Ashkenazic tradition no blessing is recited. The blessing for washing hands is said only before eating bread. Following Kiddush, one washes one's hands in preparation for karpas, vegetables dipped in liquid, even though one is not about to eat unleavened bread. Whenever one eats something that is dipped in liquid, one must was one's hands since one's hands may become moist and one might inadvertently touch something and contract impurity. We have explained that it is good to find a reason for washing one's hands prior to this. It need not be after Kiddush since we are not careful regarding impurity today.