Professor Martin Warren of the University of Kent at Canterbury said there was little doubt the king was at risk of porphyria, but it was his exposure to arsenic that led him to have several severe attacks after the age of 50.
Writing in the journal The Lancet, Professor Warren and his colleagues say that the king was given an "emetic tartar" medicine made from antimony, which is known to have been contaminated with relatively high levels of arsenic. "The presence of arsenic in a sample of the king's hair provides a plausible explanation for the length and severity of his attacks of illness, and contamination of his antimonial medications is the probable source of the arsenic," Professor Warren said. "We propose that exposure to arsenic would exacerbate attacks of porphyria in a genetically predisposed individual. We feel the case for porphyria is as strong as we can make it," he added.
Madness of King George was 'caused by arsenic'
https://www.independent.co.uk/news/uk/this-britain/madness-of-king-george-was-caused-by-arsenic-300722.html#:~:text=Scientists%20believe%20the%20arsenic%20may%20have%20caused%20the,such%20severe%20attacks%20so%20late%20in%20his%20life.