A physician administers a leech in an illustration from 1827. For many centuries, bloodletting with leeches was used to rebalance body 'humours
WELLCOME COLLECTION/GETTY IMAGESWhy were leeches used to treat the sick?
Leeches were used for bloodletting, a treatment based on the humoral theory described by the Greek physicians Hippocrates (c460–370 BC) and Galen (AD 129–216). This model, which dominated understanding of illness and medicine for millennia, held that four body fluids – phlegm, blood, yellow bile and black bile – had to be in balance to maintain health.
A patient whose skin was red from fever was believed to have too much blood, so letting would rebalance the proportions of body fluids and restore health. Whether treating skin disease, laryngitis, gout or even polio, leeching was a go-to remedy. It probably dates back even further, to ancient India and Egypt, where its use was recorded some 3,500 years ago. It reached a peak in the 19th century, then fell out of favour.
Leeches are still used medicinally, though. Since the 1980s, many plastic-surgery units have applied leeches to draw off excess blood and reduce congestion around wounds, thereby improving results. Leeches are clean, and even have an antibacterial effect.
Dr Carol Cooper, author of The History of Medicine in (Aurum, 2024)
