What are two poisons we cannot live without?

Two poisns we cant live without are dangerous as it reacts with water to form carbonic acid and this would change the pH of your body and affect your enzymes which will kill you. Thats why we need to constantly breathe out. I dont know another one it could be proteins because too much protein can cause elephantitis and will kill you so anything you eat if potentially poisonus if you have too much of it.

We cannot live without sodium and chlorine