As a dye for wool and silks; as colorant in food, drugs, and cosmetics. In biochemistry as an adsorption-elution indicator for chloride estimations. Tartrazine (otherwise known as E number E102, C.I. 19140, or FD&C Yellow 5) is a synthetic lemon yellow azo dye used as a food coloring. Tartrazine appears to cause the most allergic and intolerance reactions of all the azo dyes, particularly among asthmatics and those with an aspirin intolerance.