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.
How it shows up on a label
Functionally interchangeable with bentonite in most mask formulas.
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
Class entry may apply
Montmorillonite is named in none of the annexes under its own name, and until 2026 that was the end of the matter. Regulation (EU) 2026/909 then added Annex III entry 381, a class entry over aluminium-containing ingredients, which caps aluminium in the finished product - 0.89% (as Al) in face and body rinse-off products, 10.59% (as Al) in face leave-on - from 1 January 2027, and which bites on composition rather than on the name printed on the pack. Montmorillonite is an aluminium-bearing smectite, and unlike kaolin and bentonite it is not covered by any of the entries entry 381 excepts. Whether a regulator reads an insoluble clay mineral as an aluminium-containing ingredient for that calculation is not settled by the primary texts, so the position is open rather than clear; a flat no-limit reading is the one answer that can be ruled out.
Regulation (EC) No 1223/2009 - no entry under its own name; Annex III entry 381 (aluminium-containing ingredients), added by Regulation (EU) 2026/909 and renumbered from 379 by the corrigendum at OJ L, 2026/90354, 5.5.2026 · source ↗
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.
