A cataplasm which comprises a plaster layer on a supporting body. The plaster layer is obtained by mixing at least a neutralized polyacrylic acid, a poly(methyl acrylate/2-ethylhexyl acrylate) emulsion in an amount of 2.5 times or more, preferably 3 times or more the amount of the neutralized polyacrylic acid on a mass basis, and water. The poly(methyl acrylate/2-ethylhexyl acrylate) emulsion has an evaporation residue of 57-61% when heated at a temperature not lower than the boiling point of the medium.本發明係提供一種膏劑，其係於支持體上具備膏體層之膏劑，且前述膏體層係混合至少聚丙烯酸中和物、質量標準為該中和物之2.5倍以上，較佳為3倍以上之聚(丙烯酸甲酯/丙烯酸2-乙基己酯)乳液、與水後所得者，且前述聚(丙烯酸甲酯/丙烯酸2-乙基己酯)乳液，利用媒體的沸點以上加熱之蒸發殘留物係57~61%。
