Alchemy:

Often little difference between scientists and alchemists in medieval and early modern times
Alchemists were generally secretive about their own work, and many searched for the 'Elixir of Life'
This new medicine made from repeatedly distilling vinegar was meant to remove all impurities from the body
Sometimes medicines were made with strong poisons to make a patient violently sick, thus being seen to prevent disease
Gullible people were prepared to pay large sums of money to alchemists in order to achieve longer life

Soothsayers:

With very few qualified doctors in medieval England people often depended on a local 'wise woman'
These women would build up knowledge over generations regarding sickness and disease