valaramech

Kurzgesagt made a video that I think is related to this. I found it rather enlightening: https://www.youtube.com/watch?v=fuFlMtZmvY0

We don’t do that here

Unless you live in California, they kinda do.

The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration

This is, effectively, how oral flee/tick medications work in animals. It basically turns the animal’s blood into a mild poison. The poison is mild enough that it doesn’t affect the animal but it’s enough to kill small insects like flees, ticks, or mosquitoes.