Abstract: Singlet oxygen quenchers containing as an active component a compound represented by the following formula or (2): ##STR1## wherein each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.10 and n are as described herein, and external compositions containing these compounds are provided for the prevention and treatment of various forms of damage to living bodies caused by singlet oxygen, and are thus quite useful as antiinflammation agents, anti-aging agents, agents preventing darkening of the skin, agents preventing protein denaturation, inhibitors against formation of sunburn cells, agents preventing lipid peroxidation, agents preventing DNA damage, and particularly in the fields of medicines and cosmetics as external compositions for the skin.