Kikka Senkō is all natural mosquito-repelling incense. As the name implies (kikka means chrysanthemum, and senkō is incense in Japanese), the coils contain powdered flowers of pyrethrum daisies, which have pyrethrins, natural compounds with insecticidal properties. The scent is a natural wood burning smell.
The difference between mass-manufactured mosquito coils and Kikka Senkō is not just the all natural materials, but the amount of the pyrethrins; it is kept at a level so that it works as mosquito repellent, not as mosquito killer as mass-produced mosquito coils. Because of this characteristic, Kikka Senkō is safe to use near children and pets.