Montmorillonite
No meaningful concern for most people; irritation is possible but rare.
Also written as: Smectite
What it is
Montmorillonite is a smectite clay mineral and the principal component of bentonite; when a label lists it separately it usually means a purified or fractionated grade rather than raw bentonite. It swells in water and carries a negatively charged surface, giving it strong oil-absorbing and thickening behaviour.
What it does well
Absorbs surface oil and thickens the formula
It behaves much like bentonite, soaking up sebum and turning water into a spreadable gel. A 2024 dermatology review of bentonites and montmorillonites also flagged anti-inflammatory and hydration effects, while cautioning that the clinical evidence is still thin.
Moderate evidence
Worth knowing
Tightening and dryness, plus the usual mined-clay trace metals
Like all swelling clays it can leave skin feeling taut if left to dry fully, and it carries the same trace lead, arsenic and cadmium that come with any mined mineral, at levels covered by the technically-unavoidable-traces rule in Article 17.
Matters most toPeople with dry or sensitive skin.
Where the EU stands
No specific restriction
Not restricted under the EU Cosmetics Regulation; no concentration limit and no warning requirement.
Sources (1)
Every link goes to the original: a journal, a PubMed record or an EU document.
- [1]The potential cutaneous benefits of bentonites and montmorillonites
Archives of Dermatological Research · 2024 · doi:10.1007/s00403-024-03456-5
These clays show promise for reducing inflammation, absorbing oil and improving hydration, but larger randomised trials are needed to confirm efficacy and safety.
