Full Idea
What is food to one may be literally poison to others.
Gist of Idea
One man's meat is another man's poison
Source
Lucretius (On the Nature of the Universe [c.60 BCE], IV.638)
Book Reference
Lucretius: 'On the Nature of the Universe', ed/tr. Latham,Ronald [Penguin 1951], p.150
A Reaction
This seems to be the origin of the well-known saying. This is not relativism of perception, but a relativism of how individuals actually respond to the world. It sums up the position with, say, the operas of Wagner.