Originally Posted by RiotFpMcgee
This is intended functionality. Riposte parrys and ripostes the attack damage, but any additional effects of the attack (stuns, poison, red buff etc) will still impact your champion.
Active: Fiora parries the next basic attack within 1.5 seconds
Toxic Shot - Each of Teemo's attacks will poison the target, dealing damage on impact and each second after for 4 seconds.
Teemo's basic attacks poison their target...
You block the basic attack, but the poison which you blocked on the dart still hits you?
That doesn't make a whole of a lot of sense. I would suggest this might be looked into and reexamined. However, thank you for commenting back upon this.