<p>It’s a 95 percent success after 3 weeks, and was studied in intractable, hard-to-treat cases; kids with huge infestations. If any doubts you wait a week and repeat… those increasing percentage of success… It is much preferable to the pesticides, which are toxic and dangerous, since this method uses nontoxic substance and kills by mechanical means. In spite of warnings to wait a week, live bugs will NOT live more than 24-36 hours off the head, and eggs will die. unless incubated at warm temperatures.</p>