“Moisture-proof backsheet” is one of those phrases you see on pad packaging that sounds reassuring: Leak protection. Reliable. Safe.
But like many pad claims, it tells you what the product claims to do, not what it’s made from.
And when it comes to period care, that distinction matters for your body, your comfort, and the planet.
What a backsheet actually is.
A pad’s backsheet is the layer on the bottom - the part designed to stop liquid from passing through the product.
It’s effective at preventing leaks, which is why pads use them. But the phrase “moisture-proof backsheet” tells you function. It doesn’t tell you material.
And because pads aren’t required to list full ingredients, brands can stop at those broad descriptions.
That’s the Bloody Fine Print.
What “moisture-proof” usually means in practice.
In the vast majority of mainstream pads, a “moisture-proof backsheet” is made from plastic - most commonly polyethylene or polypropylene.
These materials do an excellent job at keeping liquid in, but they come with trade-offs:
1. Long life in the environment
Plastic backsheet layers do not biodegrade. Once they enter the landfill or the environment, they can persist for hundreds of years.
That’s a stark contrast to other parts of a pad that may be plant-based or marketed as more eco.
2. Knocks sustainability claims off balance
When the rest of a pad is made from cotton or bamboo, it can be tempting to think a product is “eco-friendly”.
But if the backsheet is plastic, the overall environmental impact remains high because that plastic layer dominates disposal outcomes.
PFAS: The hidden chemicals behind “moisture-proof”
There’s another reason this matters.
Per- and polyfluoroalkyl substances (PFAS) - a large family of synthetic chemicals - are widely used to impart waterproofing and stain resistance in consumer goods.
PFAS are sometimes called “forever chemicals” because they:
-
Persist in the environment.
-
Do not break down easily.
-
Can accumulate in wildlife and human tissue.
And here’s the part that’s relevant to period care:
Studies have found PFAS in products with plastic barriers used for moisture resistance, including menstrual products. The U.S. study analysing menstrual products detected trace levels of PFAS chemicals in several pad and liner samples, likely linked to materials used to make moisture barriers and coatings.
Because PFAS are often not listed or required to be disclosed on packaging, this use can go unseen - buried behind terms like “moisture-proof backsheet” or “protective layer”.
Why plastic backsheets matter for bodies.
It’s not just the environment.
Plastic against skin can:
-
Trap heat and moisture.
-
Increase friction.
-
Contribute to irritation like pad rash.
That’s one reason materials that promote breathability and airflow are increasingly being discussed in dermatology and textile science - especially for products meant to sit against intimate tissue for hours.
If you don’t know what that “moisture-proof backsheet” is made of, you can’t make an informed choice about comfort or irritation.
What transparency actually looks like.
At Mooncup, we don’t hide behind vague language.
We tell you exactly what each layer is made from - including the backsheet.
Instead of generic terms like “moisture-proof barrier,” we describe:
-
The materials used
-
Any relevant certifications
-
Why we chose that material
That way you get information, not reassurance language.
This isn’t about fear — it’s about visibility.
We’re not saying every plastic backsheet is inherently dangerous.
But when a product’s description stops at what it does, not what it is, people are left guessing what’s touching their bodies and what’s going into the environment.
And that’s exactly what the Bloody Fine Print exists to expose.
Once you start reading past the claims, it’s hard to unsee what’s missing.
Blog disclaimer
Our blog is intended to share information and ideas around periods, health, and sustainability. While we do our best to keep content accurate and up to date, things can change over time. The information here is not intended as medical advice — for any health-related concerns, please consult a qualified healthcare professional. For more information on our claims, please see our Claims Page, and for the most up-to-date product information, please visit our Product Pages.
