This achievement is obtainable in Act 4 (Human Body), level 2 (Slightly Acid) Nausea is triggered when your liquid touches these little orange bulb/node like things scattered around the level. When these are activated, a red beam will go through the level, destroying any part of your liquid that touches it. The video below will do a better job of explaining it to you than I will.
Yes, I know the video is for the PS3 version.
No, I don't care.