Red Dye No. 4 was an artificial coloring agent commonly used in food production and consumer products in the United States. In the mid-1970s, the US Food and Drug Administration (FDA) conducted an investigation into the safety of various food additives, focusing particularly on the potential adverse effects when ingested over an extended period. During these assessments, researchers discovered that Red Dye No. 4 was linked to the development of malignant tumors in the bladders of dogs subjected to the dye in controlled studies. This alarming finding prompted the FDA to act decisively by banning the substance from use in food products.

The testing involved feeding controlled amounts of Red Dye No. 4 to laboratory dogs over time to observe their health effects. The presence of tumors raised significant ethical questions regarding animal testing and food safety standards. As a result, the FDA's decision marked a pivotal moment in food regulation, emphasizing the importance of thorough safety assessments prior to the approval of food additives. The regulatory landscape was influenced by the findings, leading to increased scrutiny of various substances and raising public awareness about the ingredients used in food manufacturing.

In the wake of this decision, food manufacturers were required to reformulate products that contained Red Dye No. 4. This created an environment for greater transparency regarding food ingredients. Consumers began to demand more information about what they were consuming, leading to shifts in marketing and product formulation strategies, as companies sought to ensure consumer confidence in their products. The incident also laid the groundwork for more stringent regulations around artificial colorings and preservatives, thereby altering the trajectory of food safety policies in the United States.