While writing my medieval trilogy, Time Enough to Love, I had reason to research medieval medicine, specifically the plants used to help cure people. In Book 3, Beleaguered, when my heroine becomes ill with the plague, she is treated with a variety of flowers and herbs. Throughout the entire series, the reader sees that plants were used extensively in the medieval world.
Because no one at the time knew what caused disease, there were many theories about why people got sick. Some said it was the will of God, others said the planets’ alignment were out of kilter. Many physicians accepted the theory of humours as reason why a body got sick. This theory stated that the body had four “humours” or fluids in it and if they became unbalanced, the person would fall ill.
Cures abounded, some based on observation of the symptoms, some based on superstition. All of them sound barbaric to our modern ears. If the humours were thought out of balance, a doctor might try to right them by bleeding the patient, sweating them, or making them vomit.
Bleeding patients as a routine treatment lasted well into the 19th century. It was accomplished by either attaching leeches to the patient or by cutting a vein and releasing the “bad blood.” The results of this procedure were not often good, usually because the patient was already in a weakened state and losing a pint or more of blood made it harder for them to fight off disease.
But plants were used regularly to treat a variety of ailments.
Headaches were treated with a combination of sweet-smelling herbs, such as rose, lavender, and sage. Current opinion held that sweet flowers would cure by getting rid of 
bad smells. During the outbreak of plague people often carried flowers in their pockets or in a sack tied to a belt to ward off the disease.
Stomach pain was treated with a potion of wormwood, mint and balm. Lavender, sage and peppermint were considered digestive aids. Peppermint is still used for this purpose today.
Head colds and coughs were alleviated with horehound cough syrup and drinks. I remember eating horehound cough drops when I was a child.
Headaches were treated with an infusion of betony.
Fever could be reduced using willow bark (which contains salicin, a similar compound to aspirin), feverfew, or selfheal. I found that an infusion of hyssop, licorice root, and thyme was also used for fever.
Lavender, in addition to being a digestive aid, was used to sweeten the air and was added to the rushes on the floor and used in sachets to keep clothes fresh. During the plague this was a very good form of prevention, because lavender is a natural insecticide and would repel the fleas that carried the plague. Lavender also plays a very important part of the love story in Time Enough to Love.
I hope this little herbalogy has shown you how far we’ve come from medicine in the middle ages, yet how much actual knowledge they had about the use of medicinal herbs.
All three books of my medieval romance series, Time Enough to Love, are currently on sale on Amazon, Smashwords, Barnes & Noble, and Apple books for .99 each:
Betrothal
Amazon B & N Smashwords Apple
Betrayal
Amazon B & N Smashwords Apple
Beleaguered
Amazon B & N Smashwords Apple
Jenna Jaxon Romance--because passion is timeless. 