Thanks! Cookies being poisoned is still kinda dumb compared to choking but i guess they needed to show more o f that shadow-y guy lol
To be fair Slime-chan was already poison immune b/c she spat it out from the og body before taking it over? unless poison would still affect her if she had some again but who knows maybe she'll get a Holy Slime power combining with her 'saint' ability
If you wanted to be very technical, it's some kind of plant-based poison. A lot of these poisons kill by blocking chemical receptors, often in the nervous system. As a human body running on slime juice with most of her physiological functions replaced by slime based ones, it's pretty reasonable to assume it won't affect her even if we don't know the full physiology of a slime.
Those poisons, like that of Nightshade, also cause gastrointestinal effects, hence the children's reaction to them, while also often tasting sweet, which is why they ate the cookies without sensing anything amiss.
Sometimes I wonder how much thought the author has put into this kind of thing. I think it's just a coincidental detail this time, but many of the past chapters have oddly on-point technical detail.
On another note, author didn't forget to make her snort out slime instead of blood, pretty funny. She was so afraid they'd notice it, when I think everyone would have assumed it was snot.