In mid-February 1869 an outbreak of illness and several deaths in Paris were traced to a widely used cosmetic product adulterated with arsenic. Contemporary medical reports and later historical accounts identify this incident as the earliest well-documented instance of mass poisoning directly linked to a beauty preparation, highlighting the dangers of unregulated ingredients in 19th-century cosmetics. Context and product By the mid-19th century, cosmetics and skin treatments were increasingly popular in European cities. Markets were supplied by a mixture of reputable apothecaries, itinerant sellers, and small manufacturers. Many preparations contained strong chemicals and pigments—some toxic—that were cheap and effective at altering appearance. Consumers had limited information about composition, and there were no comprehensive public-safety regulations for cosmetic formulations. Outbreak and investigation On or about 16 February 1869, clinicians in Paris reported multiple patients presenting with symptoms consistent with arsenic poisoning: severe gastrointestinal distress, vomiting, diarrhea, weakness, and in some cases, fatal collapse. Physicians and local authorities investigated common exposures and identified a cosmetic powder—used to whiten the face and hands—as the likely vehicle. Chemical analysis available at the time, supplemented by later historical reviews, confirmed the presence of arsenic in the product. Scale and consequences Sources from the period and subsequent scholarship differ on exact numbers, but the incident affected dozens of users and resulted in multiple deaths. The episode prompted public alarm in Parisian society and drew attention from municipal officials and the medical press. It also led to calls for greater oversight of cosmetic ingredients and clearer labeling of preparations sold to the public. Wider significance Historians of medicine and public health cite the 1869 case as an early example of the hazards posed by unregulated consumer goods, particularly personal-care items applied directly to skin. The incident prefigured later public-health reforms and standards for product safety, even though comprehensive regulation of cosmetics would not emerge until decades later in many countries. Uncertainties and sources Precise casualty figures, the exact manufacturer, and the full distribution chain remain incompletely documented in surviving records; contemporary press reports varied and some municipal archives are fragmentary. The characterization of this event as the “first known” mass poisoning linked to a cosmetic is based on available published medical and journalistic accounts from the 19th century and on later historians who surveyed earlier episodes. If earlier, less-documented incidents occurred, they have not been conclusively established in the historical record. Legacy The 1869 arsenic-in-cosmetics case stands as a cautionary episode in the history of consumer safety. It illustrates how fashionable demand, cheap chemical additives, and limited oversight combined to create serious public-health risks—and how such crises helped spur the gradual development of product-safety awareness and regulatory frameworks in the modern era.