PROBLEM TO BE SOLVED: To provide a percutaneous administration agent which has excellent safety for animals, has high efficacy, and can sustain the efficacy for a long period, on the control of animal ectozoa, while treating methods each comprising dropping, coating, or the like, an insecticide-containing liquid on the surfaces of animals are known as methods for controlling insect pests parasitizing on the surfaces of the animals, the so-called ectozoa. SOLUTION: This percutaneous administration agent for the control of animal ectozoa comprises 1-methyl-2-nitro-3-[(3-tetrahydrofuryl)methyl]guanidine and a solvent consisting mainly of N-methyl-2-pyrrolidone.
