Tartrazine (also known as FD&C Yellow 5, Acid Yellow 23, and Food Yellow 4) is a synthetic lemon yellow azo dye primarily used as a food coloring. It may also be referenced as E number E102, C.I. 19140. In addition to being a colorant in food, drugs and cosmetics, it can be used to dye silk and wool. It serves as a dye for wool and silks, a colorant in food, drugs and cosmetics.
Many foods contain tartrazine in varying proportions, depending on the manufacturer or person preparing the food. When in food, tartrazine is typically labelled as "color", "tartrazine", or "E102", depending on the jurisdiction, and the applicable labeling laws (see Regulation below).
Products containing tartrazine commonly include processed commercial foods that have an artificial yellow or green color, or that consumers expect to be brown or creamy looking. It has been frequently used in the bright yellow coloring of imitation lemon filling in baked goods.

Foods containing Tartrazine may include ice cream, ice pops, popsicles, candy, gummy bears, cotton candy, instant puddings, gelatin, cake mixes, pastries, custard powder, marzipan, biscuits, and cookies. Beverages containing Tartrazine may include soft drinks, energy and sports drinks, powdered drink mixes, fruit cordials, and flavored/mixed alcoholic beverages. Snacks containing Tartrazine may include flavored corn chip, chewing gum, popcorn, and potato chips. Condiments and spreads containing Tartrazine may include jam, jelly, marmalade, mustard, horseradish, pickles, and processed sauces. A number of personal care and cosmetics products may contain tartrazine, usually labelled as CI 19140 or FD&C Yellow 5, including: Liquid and bar soaps, green hand sanitizer, moisturizers and lotions, mouth washes, perfumes, toothpastes, shampoos, conditioners, eyeshadow, blush, face powder and foundation, lipstick, nail polish, nail polish remover, temporary tattoos, and tanning lotions.