What is a sanitary pad actually made of?

A modern sanitary pad is a layered composite, not a single material: a soft topsheet against the skin (usually non-woven fabric or cotton), an absorbent core underneath (wood-pulp fibre blended with a superabsorbent polymer, or SAP), and a waterproof backsheet (usually a thin polyethylene film) holding it all together, with an adhesive strip to keep it in place.

Quick facts

• Topsheet: the layer that touches skin — non-woven polypropylene or polyethylene fabric, or cotton in cotton-specific pads — designed to feel soft and let fluid pass through quickly rather than sit on the surface

• Acquisition/distribution layer: an often-overlooked middle layer that pulls fluid away from the topsheet fast and spreads it across the core, preventing one wet spot from saturating early

• Absorbent core: a mix of fluff pulp (processed wood cellulose) and superabsorbent polymer (SAP, typically sodium polyacrylate) — the SAP is what turns liquid into a locked-in gel, which is why modern pads can be thin and still hold a lot

• Backsheet: a waterproof, usually breathable, polyethylene film on the underside that stops leaks onto clothing while letting some air through

• Adhesive + wings: hot-melt pressure-sensitive adhesive strips secure the pad to underwear, with the same adhesive typically on the wings, which fold around the underwear's edges for extra grip

How the layers work together

Think of a pad less as a single absorbent pad and more as a small engineered system, where each layer has one job and hands off to the next. Menstrual fluid first meets the topsheet, which is built to let it through quickly rather than pool on the surface — that's what keeps the pad feeling dry against skin even while it's actively absorbing. Just beneath that, an acquisition-distribution layer grabs the fluid and spreads it sideways across the pad, so the absorbent core gets used evenly instead of overloading in one spot (a problem engineers call "gel blocking," where too much fluid hitting one area of SAP too fast can actually slow further absorption).

The absorbent core does the heavy lifting. It's typically a blend of fluff pulp — the same kind of processed wood cellulose used in the earliest 1920s pads — with superabsorbent polymer added in. SAP is the newer part of the story: it's the same category of material used in baby diapers, capable of absorbing many times its own weight in fluid and locking it into a gel so it doesn't come back out under pressure, which is what lets today's pads be far thinner than the bulky pads of even 20 years ago.

The backsheet, on the underside, is the pad's waterproofing — a thin polyethylene film, sometimes microporous so a little air can still pass through even though liquid can't. Finally, hot-melt adhesive strips (a category of glue also used in packaging and other consumer products, formulated here to be skin-safe on the wings and secure on the back) hold the whole thing in place against underwear.