Period underwear: “absorbency” is not a standard either

This site has now made the same observation three times in three different categories — “waterproof” on jewelry, “surgical steel” on piercings, and now absorbency ratings on period underwear. An official-sounding measure with no standard behind it is the most reliable signal in consumer goods that you are being asked to trust a brand instead of a number.

Absorbency ratings are brand-invented

“Light,” “moderate,” “heavy,” “holds four tampons” — none of these are standardised across manufacturers, and there is no body checking them. One brand's heavy is another's moderate. The tampon-equivalence figures are particularly slippery, because they are derived from laboratory absorption tests using fluids that do not behave like menstrual fluid.

The practical guidance that survives all of this is simple and does not depend on the label: change every eight to twelve hours regardless of what the rating says, and treat the first cycle with a new pair as a test rather than a commitment. Buy two pairs before buying six.

The PFAS question, answered honestly

PFAS — the group of persistent fluorinated chemicals used for water and stain resistance — have been detected in some period underwear. Two things follow, and both get mangled.

First: synthetic does not mean PFAS. Polyester, nylon and elastane are not PFAS, and a garment containing them is not thereby contaminated. PFAS are a separate additive, present only if applied deliberately during manufacture, usually for water repellency. The alarm that treats all synthetics as suspect is wrong.

Second: a “PFAS-free” claim on a label is not evidence. It is a claim, it is not regulated, and testing for these compounds requires specialist laboratory work. The only thing that answers the question is third-party test documentation the brand will show you. A brand that has paid for that testing will publish it; a brand that only prints the phrase has told you nothing.

So the useful action is narrow and concrete: ask for the test report. Treat the answer — including a non-answer — as the information.

The laundry habit that destroys them

Fabric softener. It works by depositing a thin coating on fibres, and the entire function of the absorbent layer is to wick fluid into itself. A hydrophobic coating defeats that directly, which is why a pair that worked for six months suddenly leaks and gets blamed for wearing out. The same applies to dryer sheets, which do the same job by a different route.

The care that keeps them working: rinse in cold water after wearing, wash cold on a gentle cycle, no softener, no bleach, and air dry. Heat is the second enemy, for the elastane reason set out in why good lingerie survives the wash — a tumble dryer degrades the elastic that holds the gusset against the body, and a gusset that has lifted away leaks no matter how absorbent the layer underneath is.

What to look for when buying

A natural-fibre top layer against skin, cotton or bamboo, because that layer is in contact all day. A gusset that extends further front and back than you think you need, since leaks are usually a positioning failure rather than a capacity one. Flat-locked seams, for the reasons in shapewear construction. And a brand specific enough about materials that you could ask it the PFAS question and expect a document rather than a sentence.