As modern bacteria become more resistant to antibiotics, scientists are looking to the past for answers… and they may have found one in a medieval recipe for eye salve.

Researchers looking back into the dusty manuscripts of our past to see if our ancestors knew of a concoction that might help heal modern ailments may have stumbled upon a goldmine when they recreated a recipe from the 10th-century Anglo-Saxon Bald’s Leechbook, one of the earliest known medical textbooks that is now housed in the British Library.

The recipe was as follows: "Take cropleek and garlic, of both equal quantities, pound them well together, take wine and bullocks gall, of both equal quantities, mix with a leek, put this then into a brazen vessel. Let it stand nine days in the brass vessel, wring out through a cloth and clear it well, put it into a horn, and about night time apply with a feather to the eye; the best leechdom.”

The recipe contains a mixture of garlic, onion, bile salts, and English white wine. After testing a number of variations, Jessica Furner-Pardoe from the UK's University of Warwick confirmed that the salve effectively killed bacteria, even after they formed sturdy biofilms, and did not damage human cells. These are key findings in the ongoing hunt for ways to kill problematic strains of Staphylococcus and Streptococcus, especially in wounds.

They tested the medieval potion on the hospital superbug MRSA and found it had the same efficacy (90% effective) as vancomycin. As such, the recipe may be especially able to treat diabetic foot infections and leg ulcers, which are unusually difficult to treat and often lead to amputation.

The find has led this interdisciplinary team of scientists to consider, for the first time, mixing natural compounds as a way to fight infections.