Answer :

The purpose of putting this in to act is to ban foods that were from different countries (so foods that American weren't used to) and to ban drugs that were illegal! 
Prior To 1906 There Were No Rules At All On Foods Or drugs As A result Patent Medicines Commonly Contained morphine and cocaine in significant quantities. There Were No labeling Requirements So People Didn't Even know What They Were Taking. There Were No Purity Requirements And No restrictions on advertising . Drug Dealers Could Claim that their Concoction Could Cure Whatever You And Your Mule . And They Often Did As A result Of these Problems . The Pure Food And Drug Act Was Passed In 1906 . The Act Did Not Prohibit. Drugs But Simply Required manufacturing to meet Standards In Labeling And Purity And Packing .