What does the foreskin actually do?
Circumcision removes tissue with a measurable function. Here's a plain-terms summary of what that tissue actually does, condensed from the site's full anatomy and bodily autonomy pages, with a link to the sources behind each claim.
Protection Well supported
In infancy the foreskin is fused to the glans and seals the opening, keeping waste away from a sensitive surface. In an adult, that same covering keeps the glans protected and sensitive to touch, rather than constantly exposed and gradually keratinized.
Mechanical gliding Well supported
The foreskin is a double layer that rolls back and forth over the shaft rather than staying fixed in place, letting skin move against skin during sex or masturbation instead of relying on friction alone. It's straightforward mechanics, and it's the single easiest difference to actually see. There is a diagram of this on the anatomy page.
Sensation Well supportedDisputed
The foreskin contains specialized nerve endings, and the largest study to map touch sensitivity across the penis with calibrated monofilaments found the single most sensitive site of all 19 tested. Whether that changes sexual experience specifically is a separate, harder-to-measure question, and genuinely disputed.
Immune & moisture role Disputed
The inner mucosa contains immune cells and keeps the glans in a moist environment. The honest complication: those same Langerhans cells are cited by researchers on both sides, considered protective by some readings and a possible entry route for HIV by others. Same anatomy, cited both ways. Worth noting: vaginal mucosa contains Langerhans cells too, and nobody proposes removing that as a precaution.
Once it's removed, it's not coming back
Consider the two possible errors. A boy left intact who later decides he'd prefer to be circumcised can have it done as an adult, with anesthetic, consent, and a choice of surgeon. A boy circumcised at birth who'd have preferred to stay intact has no equivalent option: he cannot regrow the ridged band, the frenulum, or the specialized nerve endings measured above. Those are gone.
That asymmetry with one path reversible, the other not, is the core of the case for waiting until he can decide for himself.
The tell
Informed adults, choosing for themselves with full information and nothing forced, overwhelmingly don't choose circumcision. Denmark's non-religious adult rate is about 0.4%. If the benefits above were as decisive as they're presented in the newborn nursery, adult men would be electing the procedure at some real rate. They aren't.