In described that the Nausea was a result of

            In the
novel Nausea, Antoine Roquentin feels that something has changed in the way he
sees objects, but he doesn’t understand why. He remembered that he felt weird
when he was holding a stone, but he was not sure if the feeling came from
himself or the stone. He recalled the strange moment as “nausea to the hands”. Roquentin
thought that the weird feeling towards objects and people only happened when he
was alone or walking in the street, but this time, he also felt the feeling
when he was in a café. Roquentin also felt the nausea when he looked at the
bartender’s purple suspenders, which he thinks sometimes appear blue. He then
realizes that the suspenders were never purple, and that color is something
that doesn’t really exist. He requests the barmaid in the café to play his
favorite song called “Some of these days” to help calm him down. When the song
started to play, it successfully made the Nausea go away, he says that the melody
of the song crushes the time of the real world, making him feel in the music. Roquentin
also felt more comfortable in the dark, because he thinks that the Nausea occurs
when he is in the light. When in a café, he got disgusted at the behavior of
the people around him, which he describes as robot-like, because he thinks that
the people are trying to hide their own existence from themselves. He then
understands what was causing the Nausea, it was his fear of existence. He described
that the Nausea was a result of colors, tastes, and smells that are not real,
and that things just exist, Anything he touches no longer has any essence.  He finally understood what was causing the
Nausea when he encounters the root of a chestnut tree. He finds that the
root’s physical characteristics mask the root’s actual existence. The cause
of Roquentin’s Nausea was because of Satre’s belief of “existence precedes
essence.” Anything used to describe an object is not only irregular but does
not really exist.