A noun in Quenya Notes (QN) from 1957 glossed “venom, poison(ousness)” derived from the root √SLOY (PE17/185). I think this applies to poison in the abstract, as opposed to hloima used for a specific venomous substance.
Quenya
hloirë
venom, poison, poisonousness
hloirë
noun. venom, poison, poisonousness
hloirëa
adjective. venomous, venomous, *poisonous
hloirëa
venomous
hloirëa adj. "venomous" (PE17:185)
hloirë noun "venom, poison, poisonousness" (PE17:185)