It's not clear to me whether a poison whose "effect" is 1d6 Dex is dealing ability damage that must be healed, or has an effect that vanishes when the poison's duration is over.
My question is primarily about whether or not poison typically does ability damage, as opposed to a penalty that would end after the poison has run its course.
Best Answer
No, the effect doesn't end when the poison does, because poisons typically do ability damage.
Per the SRD, poisons do ability damage. I realize the table on that page might be slightly ambiguous, so have an example of each type, contact, ingested, inhaled, and injury. The examples further clarify that the damage is indeed ability damage (although, one of them also does ability drain separately from its ability damage, keep an eye out for poisons that do other things besides just ability damage).
I found a better general explanation, on the afflictions page (which poison is considered one of):
This means that the decrease does not go away when the effect ends.