NG+. Wolf school gear part three.
I killed the Ice troll and had to enter the cave filled with yellow gas.
My health went down so quickly I died over and over again.
I tried using igni to disperse the gas but this did not work.
Is there a concoction I'm supposed to consume? Even when
I am in an area free of gas my health still drops quickly.

The gas WILL kill you. It is there to kill you. Don't use Igni, that is too dangerous. Use Aard, move, use Aard, move... etc.

Use aard? interesting. I only used igni because that is what a play through recommended.
I'll have to go back and try again but will have to kill that Ice troll again.

UPDATE: Using aard made this a cake walk.
I remember "Wandering in the dark" - Wikia states that igni must be used to get rid of the pockets of gas.
That shows you, one cannot believe everything one reads.