Fennings Fever cure contained diluted nitric acid which is on the 'hazardous substance list' and is toxic.
This website shows the 'snake oil' remedies used in victorian days.
http://chesterrep.openrepository.com...am%20Press.pdf
analysis of Fenning's Fever Cure which revealed that the 'cure' was merely a dilute solution of nitric acid and peppermint