An adhesive which comprises aqueous and nonaqueous polymers suitable for holding an lipophilic drug, etc., and has tackiness and cohesiveness which are sufficient for the plaster of a patch; and a patch employing the adhesive. The adhesive contains a polymer which comprises one or more kinds of acrylic or methacrylic monomer units, at least one kind of the monomer units having a hydroxy group, and which has been crosslinked with a boron compound.