What can increase a pet's susceptibility to pesticide poisoning after a recent treatment?

Prior treatment with the same pesticide can indeed increase a pet's susceptibility to pesticide poisoning. This occurs because repeated exposure to the same active ingredients can lead to an accumulation effect in the pet's system, overwhelming their ability to metabolize and detoxify the chemicals effectively. Over time, a pet's liver and kidney may become stressed or impaired, making it more vulnerable to adverse effects when exposed again to the same pesticide.

In contrast, being treated with different active ingredients, outdoor treatments, or the absence of other animals does not inherently build a cumulative risk in the same manner nor affect how the pet’s body processes the chemical. Each of these situations might present other concerns, but they do not have the direct physiological impact regarding increased susceptibility to the same pesticide as prior exposure does.