Human Saliva, Metzitzah, and the Wisdom Encoded in Torah: A Medical Reflection
What follows is, I believe, genuinely fascinating — a convergence of ancient Jewish practice and cutting-edge science that deserves careful attention.
The Opiorphin Discovery
In November 2006, researchers at the Pasteur Institute in Paris announced the discovery of a powerful natural painkiller found in human saliva, which they named opiorphin. In animal studies, it proved several times more potent than morphine, with just 1 mg per kilogram of body weight matching the effect of 3–6 mg of morphine per kilogram. Unlike synthetic opiates, opiorphin is a naturally occurring molecule that the body metabolises quickly, potentially making it safer and more targeted than existing painkillers.
Dr Ed Ross of Brigham and Women’s Hospital in Boston called it a potentially significant addition to the body’s known natural pain-relieving compounds, noting that it appeared considerably more powerful than endorphins, which have long been recognised but are clinically limited by their short duration and relative weakness.
The Eighth Day: A Biological Precision
The Torah commands in Leviticus 12:3 that circumcision be performed on the eighth day of a male infant’s life. What modern medicine has confirmed is remarkable: the eighth day is the precise point at which an infant’s blood clotting factors — particularly prothrombin (Vitamin K-dependent) — reach their peak levels, actually exceeding normal adult values. Before that day, they are suboptimal; after that day, they return to normal levels. The eighth day is, by measurable biological criteria, the safest possible day for a circumcision to be performed.
This is not a coincidence that passes without comment.
Metzitzah: Ancient Practice, Modern Vindication
The practice of metzitzah — the drawing of blood from the circumcision wound by mouth, performed by the mohel — has been controversial in modern times, primarily due to legitimate concerns about the transmission of certain infections in rare cases. This reflection does not seek to adjudicate that ongoing halachic and medical debate, and no criticism of mohelim who follow contemporary alternative protocols is intended here.
What is worth noting, purely from a medical-scientific perspective, is this: human saliva contains a remarkable array of antimicrobial, coagulation-promoting, and now apparently analgesic compounds. The discovery of opiorphin adds a new dimension to what was already known — that saliva contains epidermal growth factor, histatins, and other agents that actively promote wound healing and inhibit bacterial growth.
Furthermore, it has been observed that morning saliva — produced before eating or drinking — has an especially concentrated antimicrobial profile, dramatically reducing the risk of pathogen transmission. This lends a medical dimension to the traditional practice of performing the brit milah early in the morning.
The synthesis is striking: the mohel’s saliva at the wound site would, in theory, provide simultaneous pain relief, antibacterial protection, and hemostatic assistance — a combination that no synthetic clinical substitute fully replicates.
A Word on Torah and Science
It bears emphasising: the Torah requires no scientific validation. Its authority does not rest on whether molecular biology catches up to its commands. But there is a particular and recurring joy in watching science — slowly, incrementally, with great effort and expense — arrive at conclusions that were encoded in Jewish law thousands of years ago. The “Healer of all flesh” (Rofeh kol basar), as we say in our daily prayers, designed the system. It is not surprising that the design holds up under examination.
These convergences are not proof — they are, perhaps, an invitation to wonder.

Human sputum