Flea and tick medications trusted by pet owners around the world may have unexpected environmental costs. The researchers found that the active ingredients from the isoxazoline treatment were passed into the feces of dogs and cats. These droppings expose insects that feed on the droppings to toxic chemicals. These insects are essential to nutrient cycling and soil health. The findings suggest that daily pet grooming can spill over into ecosystems. Treatment against fleas and ticks can thus harm wild animals.