Is Glass Skincare Packaging Actually Safer Than Plastic?
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If you've switched to skincare products in glass jars to avoid microplastics, the logic is sound; glass is inert and hasn't been found to shed microplastic particles. However, there are some hidden risks you should be aware of. Recent scientific evidence research has found:
- Metal caps or lids with painted exteriors can contaminate glass packaging with microplastics;
- Foil seals found inside skincare products can also shed microplastics; and
- Skincare ingredients, like alcohols, acids, and essential oils, can accelerate leaching from plastics they come into contact with.
Where the contamination comes from: the cap
In 2025, researchers from the French Agency for Food, Environmental and Occupational Health and Safety (ANSES) published a study measuring microplastics across different beverage types and container formats, including glass bottles, plastic bottles, cans, and cartons. They found that beverages in glass bottles showed elevated microplastic levels compared to other formats, and the source wasn't the glass.
When researchers cleaned the metal caps with air, water, and ethanol before sealing, microplastic levels dropped by approximately 70%, from 287.3 to 86.7 particles per liter. The exterior paint on the caps, which flakes during transport and storage as caps rub against each other, was identified as the primary source of contamination. Scratches on the outside of tested caps were observed, with corresponding paint particles found on the cap interiors—and in the product.
Wine showed notably lower microplastic levels than other beverages in the study, consistent with the fact that wine is more commonly sealed with natural cork than painted metal.
A second source: the seal you peel off on first use
Most skincare products include an induction seal, a foil disc you peel off when you first open a new jar. These seals are standard across cosmetic, pharmaceutical, and food packaging, and they are typically made with plastic layers.
A 2025 study published in the Journal of Hazardous Materials directly measured microplastic particles released when these sealing liners are peeled. The liners are a laminated structure: aluminum foil bonded to a plastic layer, typically polyethylene terephthalate (PET) or polyethylene (PE), using wax and a heat-activated adhesive. The researchers found approximately 625 microplastic particles releasable per square millimeter of liner surface.
Skincare products use induction sealing as tamper evidence. But this study suggests that the seals can inadvertently introduce microplastics into the product.
What the skincare and cosmetics research shows
The studies above use packaged beverages as a proxy, which is where most of the packaging research has been done. But the mechanisms transfer to cosmetics, and some evidence now concerns skincare products specifically.
A 2026 study published in MDPI directly detected and quantified microplastics in 21 skincare and treatment cream samples, noting that contamination from processing and packaging materials "cannot be ruled out" as sources.
Separately, a 2024 critical review by researchers at the University of Birmingham found that of 2,381 cosmetic products studied in the peer-reviewed literature, only two were leave-on products (such as moisturizers, creams, and sunscreens). The researchers called for urgent investigation into this understudied category.
There's also a less-obvious chemical factor: the same Birmingham review found that common skincare formulation ingredients (e.g., alcohols, acids, and essential oils) can actively accelerate leaching from plastic components they contact, including cap liners. The formulation itself may be pulling plastic particles out of the seal it sits beneath.
What you can do about this
There's currently no reliable way to know whether a specific skincare product contains microplastic contamination from its packaging, or at what level. The research in leave-on cosmetics is early, and no label is required to disclose incidental contamination.
At KnowLabels, we test skincare products for microplastics, including contamination from packaging and manufacturing. Join our waitlist to learn more about what you are putting in your skin.
Frequently asked questions
Is glass skincare packaging safer than plastic when it comes to microplastics?
Not necessarily. Glass itself doesn't shed microplastics, but the metal caps and induction liners used to seal glass jars are documented sources of microplastic particles. The contamination risk can also result from the cap and seal, not just the container.
Where do microplastics in glass skincare jars come from?
Research points to two primary sources: the painted exterior coating on metal caps, which flakes during storage and transport as caps abrade against each other; and the plastic bonding layer in induction foil seals, which releases particles when peeled. Both are standard components of premium glass skincare packaging.
Do metal lids on skincare jars release microplastics?
Based on current evidence, yes it can. A 2025 study found that cleaning metal caps before sealing reduced microplastic contamination in the contents by approximately 70%, directly implicating cap coatings. Around 30% of contamination remained after cleaning, from sources not yet isolated by the research.
What is an induction seal, and does it matter?
An induction seal is the foil disc you peel off when first opening a sealed jar. It contains a plastic bonding layer, typically PET or PE, bonded to aluminum foil. A 2025 study found that peeling this seal releases approximately 625 microplastic particles per square millimeter of liner surface. These seals are widely used in cosmetics, supplements, and pharmaceutical packaging.
How would I know if my skincare products contain microplastics from packaging?
There is no label or certification that currently discloses microplastic contamination from packaging or manufacturing in the US or EU. Lab-based testing is the only way to know what's in a specific product.
Sources
- Microplastic contaminations in a set of beverages sold in France (ANSES, Journal of Food Composition and Analysis, 2025) — DOI: 10.1016/j.jfca.2025.107719 / ANSES official summary / phys.org coverage
- Microplastics and nanoplastics released by peeling off aluminium foil cap sealing liners — Liu & Naidu (Journal of Hazardous Materials, October 2025) — ScienceDirect / PubMed
- Identification, quantification, and characterization of microplastics in skincare and treatment creams (MDPI Cosmetics, February 2026) — MDPI
- Beyond microbeads: examining the role of cosmetics in microplastic pollution — critical review of 2,381 products (University of Birmingham, Journal of Hazardous Materials, 2024) — ScienceDirect