Sodium polyacrylate
What it is
Sodium polyacrylate is the superabsorbent polymer at the core of every modern disposable diaper — the crystal-like granules that turn liquid into a gel and hold many times their weight in moisture. It's a synthetic polymer, not a natural material, made by polymerizing acrylic acid and neutralizing it with sodium hydroxide, then cross-linking the chains so the gel stays put instead of leaking back out under pressure.
Why it's flagged
It gets flagged mostly on reputation rather than current evidence: a 1980s-era link between superabsorbent tampon fibers and toxic shock syndrome, plus recurring online claims connecting polyacrylate diaper gel to reproductive harm, have kept it on "ingredients to avoid" lists for decades. The tampon-fiber material involved was a different, discontinued product, and the toxic-shock mechanism (bacterial toxin production, not chemical toxicity) doesn't apply to a diaper's absorbent core. Separately, unreacted acrylic acid monomer — a genuine irritant — can be a trace residue of manufacturing, which is why regulators track purity limits rather than banning the polymer itself.
How concerned to be
Generally fine. The Cosmetic Ingredient Review expert panel, which re-evaluates ingredient safety as new data emerges, has found sodium polyacrylate safe as used in personal-care and absorbent products, and it's classified as inert for EPA pesticide-formulation purposes at the low residual monomer levels manufacturing standards require. It's a reasonable ingredient to stop worrying about; the genuine diaper-safety conversation is elsewhere — in fragrance, lotion additives, and bleaching byproducts.
What it's called on a label
Look for any of these on an ingredient list: Superabsorbent polymer, SAP, Polyacrylate, Cross-linked sodium polyacrylate, Sodium polyacrylate, Acrylic acid, sodium salt, polymer.
Sources
- Safety Assessment of Alkyl Acrylate Crosspolymers as Used in Cosmetics, Cosmetic Ingredient Review (CIR) Expert Panel (2020)
- Toxic Shock Syndrome Information for Health Care Professionals, U.S. Food and Drug Administration (2023)