Background: Although poisonings due to a toxic substance being decanted into a secondary container are often reported to poison centers, we were unable to locate prior European data about their circumstances, incidence and consequences. We sought to describe the circumstances and outcomes of this behavior. Materials and method: We conducted a prospective study of all poison exposures involving transfer to a secondary container reported to our poison center during a six month interval (January 1, 2021 through June 30, 2021). We called patients and clinicians for follow up the next day. We used a prepared questionnaire and added the responses to the national database for French poison centers. Results: We identified and included 238 patients (104 male, 134 female) with a median age of 39 years [range 0-94 y]. Exposure was mainly oral (n = 221), the secondary container was mainly a water bottle (n = 173), toxic substances were essentially cleaning products (n = 63) or bleach (n = 48). Symptoms were gastrointestinal (vomiting, diarrhea, abdominal pain) (n = 143) or respiratory (cough, dyspnea, aspiration pneumonia) (n = 15). The World Health Organisation/International Programme on Chemical Safety/European Commission/European Association of Poison Centres and Clinical Toxicologists Poisoning Severity Score was none in 76 cases (31.9%), minor in 147 (61.8%), moderate in 12 (5%), and severe in three cases (1.3%). Products that led to severe poisoning contained either ammonium hydroxide or sodium hydroxide. Two of the patients required intensive care treatment. At the end of the follow-up, 235 patients fully recovered, and three patients had sequelae. Conclusions: The study illustrates the risk of toxic substance transfer. Water bottles were the secondary containers in most exposures to decanted substances. Most had minor or no effects, but nearly one-quarter were admitted to the hospital. The few severe exposures involved either ammonium hydroxide or sodium hydroxide.