This document summarizes information about PTC sensitivity, which is the inability to taste bitter compounds like phenylthiocarbamide (PTC). It notes that approximately 30% of the world's population is PTC blind/insensitive. The causes are genetic - a variant in the TAS2R bitter taste receptor gene. Being PTC blind means an inability to detect bitter tastes, which could pose risks by not recognizing poisonous substances. Tests for PTC sensitivity involve tasting strips or cheek cell DNA analysis to determine one's genetic profile for this trait. Those who are PTC blind may need to take dietary precautions like checking expiration dates more closely.