A plaster including a pressure-sensitive adhesive layer containing a readily dissolvable agar and at least one additive selected from the group consisting of polyacrylamides, polyvinyl alcohols, polyvinyl pyrrolidones, sodium alginate, ammonium alginate, carboxymethylcelluloses, sodium carboxymethylcelluloses, methylcelluloses, gum arabics, tragacanth gums, and xanthene rubbers, is provided.
