What the heck are "ingested sydromes!?"
Syndromes are illnesses your dwarves can suffer due to different sources of venom; such as bitings, poisonous spit or fumes, and maybe a couple more; usually caused by forgotten beasts, and some animals (such as cave spiders). Syndromes can range from the annoying to the instantly fatal, through the gross and disturbing (rot of limbs or tissues).
I guess that "ingested syndromes" means that if your dwarves are stupid enough to finely mince giant cave spider meat into +large cave spider biscuits+, or do something similar with other noxious critters, they're going to get the whole fort sick. Will probably bring more uses to the allowing/forbidding of ingredients in the kitchen z-sub-screen.
Just guessing though.