Phenolphthalein
A compound used as a laboratory reagent and acid-base indicator and also used in over-the-counter (OTC) laxative preparations.
Phenolphthalein may be a carcinogen (cancer-causing agent).
Feeding of phenolphthalein caused cancer in multiple organs in multiple species of experimental animals.
The US government in 2000 classified phenolphthalein as 'reasonably anticipated to be a human carcinogen.'