Porphyria is a metabolic illness that afflicts many MCS sufferers. It might possibly affect the majority of MCS sufferers, but since not all varieties of Porphyria can be tested for, we just don't know. But in a practical sense, that doesn't matter because the lists provide a strong tool for doctors to use in trying to accommodate those with chemical sensitivities.
The doctors were very happy to have something in hand to refer to, especially a list that not only gave drugs to avoid but ones that were most likely safe to use.
The two lists we used for Cynthia's surgery are available at: www.porphyria.uct.ac.za/druginfo/drug-frameset-group.htm and