These drops kill fleas—but they’re getting into everything.

MENDOCINO CO., 8/5/26 — The monthly flea control you squeeze between your dog’s shoulder blades is built to spread. It collects in the oil glands of the skin and seeps back into the coat for weeks, which is how it reaches the flea. It also comes off on your hands, into the dog’s bed and down the bathtub drain. On July 31, state regulators said they have five years of sampling that shows where it goes next.

The California Department of Pesticide Regulation released its final risk memo on fipronil, the active ingredient in many over-the-counter spot-on flea and tick products. The department posted the memo along with its written answers to seven comment letters filed on the December draft. Both documents are on the department’s website here and here.