How does debuff/buff stacking work?

Laceros

If poisons have a stacking 30% regen reduction why doesnt 3 poisons cancel healing?

Pikolu

3*30=90%

Laceros

Even with over 3 poison, champs can still heal

Pikolu said:

3*30=90%

ahmynuts

Laceros said:

Even with over 3 poison, champs can still heal

Pikolu said:

3*30=90%

Which champs? Are you taking abilities and aar into consideration?

AverageDesi

Poison reduction does not stack on base. It stacks on current regen. So 30% of 30% of 30% of 100%.
So you're left with around 34.3% healing