The present invention addresses the problem of developing an additive that makes it possible to provide an ideal sunscreen cosmetic of which the UV protective ability is improved by heating. An additive for enhancing the UV protective effect of a sunscreen cosmetic by heating, the additive being characterized by including at least one selected from the group consisting of amphiphilic substances or moisturizers having an IOB value of 5.0 or lower. The amphiphilic substance or moisturizer is preferably a polyoxyalkylene-polyoxyethylene copolymer dialkyl ether and/or polyhydric alcohol.本發明之課題在於開發一種能夠提供紫外線防禦能力藉由加熱而提昇之理想防曬化妝料之添加劑。本發明之添加劑用以藉由加熱而增強防曬化妝料之紫外線防禦效果，其特徵在於包含選自由IOB值為5.0以下之兩親媒性物質或保濕劑所組成之群中之至少1種。上述兩親媒性物質或保濕劑較佳為採用聚氧伸烷基·聚氧乙烯共聚物二烷基醚及/或多元醇。
