In France, the industrialisation period has seen a number of economic and social transitions. The epidemiological transition experienced during this time led to the emergence of diseases linked to this specific context (e.g. respiratory and cardiovascular diseases) and modifications in the prevalence of deficiency diseases such as rickets (vitamin D) and scurvy (vitamin C). However, it was also a period of major scientific progresses, particularly in medicine and pharmacy. As a result, treatments for deficiency diseases have changed. An exhaustive review of these treatments in the medico-historical literature (medical treatises and theses, ancient pharmacopoeia, archives) has enabled us to identify both plant-based (including for example rhubarb, opium, cinchona) and animal-based treatments (e.g. after 1850, cod liver oil, the only effective treatment against rickets) or treatments containing metal elements, particularly mercury. The latter is now recognised as extremely toxic, but has been widely used in many forms for medical purposes since the 17th century. We present here the results obtained on the individual SP5 from the Rue Thubeuf cemetery (Rouen, late 18-19th centuries, France), a 3-4-year-old child showing signs of multiple bone deficiencies, probably rickets and scurvy. Bone and tooth samples from SP5 have been analysed through a palaeopharmacological approach, using an archaeometric strategy in three stages to: 1- detect mercury (X-ray fluorescence), 2- quantify it (CV-AAS) and 3- localise it in the mineral matrix (LIBS). The ED-XRF spectrum of the bone sample revealed a mercury peak, absent in the dental sample and the CV-AAS analysis showed a high concentration of mercury in the bone (9.373 mg/kg ± 10% uncertainty). This preliminary archaeometric study revealed an abnormal concentration of mercury, suggesting a potential severe ante mortem intoxication. The potential sources of contamination have been discussed and ruled out, reinforcing the hypothesis of mercurial treatment.Read less <