28 September 2023
Dr Freya Harrison and Dr Christina Lee used Bald’s Leechbook – a 10th-century medical text held by the British Library – to find a potential cure for persistent infections in the modern world. In 2021, Freya was awarded the WH Pierce Prize for this research.
Freya is a Reader in Microbiology at the University of Warwick. Christina is an Associate Professor of Viking Studies at the University of Nottingham.
My research is about health and healing in early medieval England: the period 500 to 1100 CE. I’m interested in the ways that people thought about illness, and how illness was treated, in a period very different from our own.
Bald’s Leechbook is clearly a book designed for the recording of knowledge. The diseases in it are organised from head to toe. The manuscript is from the early 10th century, from the south-west of England. We don’t know who Bald is. It’s named after him simply because the colophon [a note from the scribe] says that this book belonged to Bald.
We’re lucky that the Library has this manuscript
This manuscript is unique, and we don’t have any other copies. I’m really pleased that it has survived the ravages of time: an awful lot of medical remedies from this period haven’t survived. We’re pretty lucky that the Library has this beauty on its shelves.
The Library is a fantastic place. It amazes me that these manuscripts are there. It’s accessible for many people, which is a very good thing. It’s also great that the Library digitised its early manuscripts, because obviously, they wouldn’t be able to stand daily wear and tear.
That link with the past is the biggest thrill
I use quite a lot of the digitised material, but there’s nothing better than going into the Manuscripts Room, knowing that the original is waiting for me there. That link with the past, the idea that I am touching something which is smiling at me from over a thousand years ago, is the biggest thrill of all.
Freya first contacted me because she wanted to join an Old Norse reading group that I ran. We got talking about what we were working on; at the time, I was writing an essay about infectious diseases. Then Freya invited me to meet her team, and that was the beginning of everything.
The remedy we tested is labelled ‘to make an eye salve against a wen’. We’ve identified the wenn as a stye in the eye which is caused by a bacteria called staphylococcus. Bald’s Leechbook tells you to use garlic, and something called ‘cropleac’. Nobody knows exactly what cropleac is. We checked every possible dictionary. Everyone agrees it’s an allium species, so we decided to use either onion or leek.
This project changed attitudes to medieval medicine
The recipe has wine and ox gall in it. You pound the ingredients, mix them, and let them stand for a while. There’s an instruction saying that you need to put them in a brass or bronze vessel. Then the book tells you to use a feather to put the medicine in the eye.
One thing I loved about this project is the way it challenged contemporary attitudes to medieval medicine. People had thought that it didn’t have anything useful to offer. Our research allowed me to highlight the idea that early medieval thinkers were no less curious or intelligent than us – but they thought in a different way. We need to remember that an awful lot of our medical research is also hit and miss, and it’s not made for everybody, so we need to be more respectful of medieval problem-solving. The strangeness of the Middle Ages has always fascinated me.
I'm a microbiologist. My interest is in bacterial infections that are really hard to treat: the kind you get when there’s a problem with your normal responses to infection. Things like lung infections in people with cystic fibrosis, and wound infections that don't heal.
I have an amateur interest in early medieval history. Several years ago, I read a paper in an academic journal about people who tried to reconstruct medieval remedies. I thought it would be cool to do something like that, and it sat there at the back of my mind for years until I met Christina and we put our heads together.
The last three words of the recipe are ‘the best medicine’
When Christina and I discussed the eye salve, it seemed that the lump in the eye that the writer describes could very easily be a stye. A stye is a bacterial infection, which was what we wanted to explore. The last three words of the recipe are ‘the best medicine’ – so how could we not try to make it?
The most difficult challenge was that the ingredients we have access to now are very different to those in medieval times. Crops have been selectively bred: an early medieval head of garlic and a modern one could have very different chemical compositions.
For the wine, we found a little vineyard near Glastonbury who were growing their own grapes, just a few miles from where we know Glastonbury Abbey had a vineyard in the early medieval period – so there were similar growth conditions. It's nice sometimes in science when you get to play: try something completely new and do some problem solving.
The first results were shocking
In infections that are hard to treat, bacteria start to secrete a kind of slime overcoat, and stick together in a big 3D structure called a biofilm. That protective overcoat makes them very hard to kill with antibiotics. We made little analogues of human soft tissue and put bacteria in them, and when they grew, they made biofilms. We added the eye salve, waited a day, then recovered the bacteria and counted how many were left alive. This was a really high bar to test – a lot of antibiotics don't do very well at killing biofilms.
The first results showed that we were getting several powers of ten reduction in the bacteria, which was shocking. We thought we’d done something wrong: we wondered if we’d accidentally put loads of alcohol in. But we found that it was repeatable. When we combined these ingredients, the amount of bacterial killing was greater than you’d expect. There are genuinely very few times in your career where you find something that's so effective.
We need new treatments that can kill bacteria
Over the past eight years, we’ve been able to show exactly what range of bacteria the eye salve can kill. We got permission to do a safety trial on human volunteers, which ended up looking pretty good. We’re not saying that it’s a wonder drug, but we want to find out what’s in there and extract the chemicals that have this effect. The most likely use of a synthetic mixture based on Bald’s eye salve would be to add it to a dressing that you would put on something, such as a surgical wound, to try to stop or reduce infection.
Most antibacterials that are promising in the lab ultimately fail, but you have to keep trying. We're in a situation where people end up with completely untreatable wound infections. A significant number of people with diabetes will have to have their foot or their lower leg amputated because of an infected wound that cannot be cleared and poses a risk of sepsis. People with cystic fibrosis still die early from respiratory failure because you cannot clear biofilm infections in their lungs. We need new treatments that can kill the bacteria that current antibiotics can't.
Bald’s eye salve has led to new research
Bald’s eye salve has led to a whole new set of research for my lab, based on the idea that medical practitioners in the past might have hit on useful cocktails of natural products. Dr Erin Connelly, who did her PhD with Christina, spotted that throughout manuscripts like this, honey and vinegar are often put together in treatment. This got us thinking about whether anyone in modern research had put them together – and nobody had.
Through testing in the lab, we found that acetic acid (in vinegar) and honey can be combined to achieve a result that’s greater than the sum of their parts. We also found that there were compounds present in some vinegars that enhanced their killing of microbes – it might be possible to find new molecules that could be developed into something useful.
Bald’s Leechbook was sitting on a shelf in the British Library
Bald's Leechbook has a remedy in it which we think is for malaria, which involves using the plant wormwood. Wormwood does contain an anti-malarial, and this was discovered by a Chinese scientist, Professor Tu You You, in the 1970s, because of an ancient Chinese remedy. She won a Nobel Prize. All the time she was doing that work, Bald's Leechbook was sitting on a shelf in the Library, and nobody had discovered that it contained remedies that could still be used.
We know that Bald’s Leechbook originally included a chapter on gynaecology and obstetrics, because it’s in the index, but it hasn’t survived. I think one of the most dangerous things anyone could do in the medieval period was to get pregnant, partly due to the risk of infection. There must be so many remedies for infection in that section of the book. I can’t help wondering where they are now.
As told to Lucy Peters