The exact mechanism of action of cyromazine against insects is unclear although it does affect the larval and pupal cuticles.

[3] The exact mechanism of action has not been determined, but it is non-toxic to mammals and does not target the nervous system.

In 2011 resistance was detected in Lucilia cuprina to cyromazine from infested sheep that failed to be protected following treatment.

[5] The Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA) provides a test method for analyzing cyromazine and melamine in animal tissues in its Chemistry Laboratory Guidebook which "contains test methods used by FSIS Laboratories to support the Agency's inspection program, ensuring that meat, poultry, and egg products are safe, wholesome and accurately labeled.

"[6][7] In 1999, in a proposed rule published in the Federal Register regarding cyromazine residue, the United States Environmental Protection Agency (EPA) proposed "remov[ing] melamine, a metabolite of cyromazine from the tolerance expression since it is no longer considered a residue of concern.