Serotonin
For information on amines in general please read the amines article.
Much has been written about the mood elevating qualities of serotonin but less has been written about the difficulties that an 'excess' can cause for certain individuals.
Some individuals experience unpleasant symptoms when the level of serotonin in their body exceeds the amount they can tolerate.
The main symptom indicators would appear to be joint inflammation with no verifiable evidence of arthritis, and migraines not responding to other solutions but other symptoms have also been noted.
Additional information on serotonin can be found in Change Your Diet and Change Your Life.