What law required manufacturers to list ingredients they used in foods and drugs?

The Federal Food, Drug, and Cosmetic Act (FFDCA) of 1938 required manufacturers to list ingredients in foods, drugs, and cosmetics. This landmark legislation aimed to ensure the safety and efficacy of these products, establishing standards that manufacturers had to adhere to, including proper labeling. The act was a response to public health concerns and helped lay the groundwork for the Food and Drug Administration's regulatory authority.