What is it?
Potassium aluminium silicate is a naturally occurring aluminium silicate mineral, chemically similar to the clay mineral muscovite mica. It is processed into a fine white powder and used in food as an anti-caking and release agent.
E-numbers / Other additives / E555
Potassium aluminium silicate
also: Potassium alum silicate · Aluminium potassium silicate
A mineral anti-caking agent added to salt and powdered foods to keep them free-flowing. Contains aluminium; a 2020 safety review could not confirm it is safe at permitted use levels.
Scan a barcode to check a food for potassium aluminium silicate. NutraSafe Pro · £6.99/month · iPhone and Android
E555
Potassium aluminium silicate
Aluminium from food additives accumulates in the body.
VeganVegetarian
How common it is in UK food
UK supermarket foods that declare E555: 2 of the 43,325 we checked (under 0.1%)
Counted by its code or its name in the ingredient list.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
What potassium aluminium silicate is, what it does and where you will see it
Why it’s worth knowing. Aluminium from food additives accumulates in the body. Exposure from E555 at maximum permitted levels could far exceed the weekly aluminium limit set by European food safety regulators, and a 2020 EFSA review found insufficient data to confirm safety.
What does it do?
The powder has a large surface area and a layered crystal structure that absorbs moisture and coats food particles, preventing them from sticking together or clumping. In salt and powdered products it keeps the granules separate and free-flowing.
Where you will see it
Found primarily in table salt and salt substitutes, powdered and icing sugar, dextrose, dried whey and whey-based preparations, and sliced cheese where it acts as a release agent between slices. On a UK label it appears as 'potassium aluminium silicate' or 'E555'.
What the science says
EFSA could not confirm safety in 2020
When EFSA re-evaluated E555 in 2020, its expert panel concluded that safety could not be assessed. The main reasons were very limited toxicological data on the compound itself and insufficient physicochemical characterisation. This is a formal data-gap conclusion, not a finding that it is harmless.
EFSA's re-evaluation panel concluded that the safety of potassium aluminium silicate (E555) as a food additive could not be assessed due to very limited toxicological data and insufficient physicochemical characterisation.
2020Regulatory reviewEFSA Panel on Food Additives and Flavourings (FAF), EFSA Journal
Aluminium exposure may exceed the tolerable weekly intake
The primary concern with E555 is its aluminium content. EFSA established a tolerable weekly intake (TWI) of 1mg of aluminium per kilogram of bodyweight per week in 2008, based on neurodevelopmental harm in animal studies. Theoretical maximum exposure calculations for E555 at its permitted use levels showed potential to far exceed this TWI, particularly for children.
EFSA set a tolerable weekly intake for aluminium of 1mg per kilogram of bodyweight per week, based on a neurodevelopmental endpoint in animal studies.
2008RegulatoryEFSA Scientific Opinion on the safety of aluminium from dietary intake, EFSA Journal
Theoretical maximum exposure calculations for E555 at maximum permitted food additive levels showed aluminium intake could far exceed the TWI, with some scenarios producing exposures hundreds of times the tolerable level.
2020Regulatory reviewEFSA Panel on Food Additives and Flavourings (FAF) re-evaluation of E554 and E555, EFSA Journal
Aluminium accumulation and neurodevelopmental concern
Aluminium is not an essential nutrient and accumulates in bone and neural tissue with repeated exposure. Animal studies underpinning the TWI identified effects on brain development as the most sensitive endpoint. Human epidemiological data on dietary aluminium is limited, and food-additive sources are one part of overall dietary aluminium intake alongside naturally occurring aluminium in food and water.
Aluminium accumulates in bone and neural tissue and is not excreted efficiently. The TWI is based on a no-observed-adverse-effect level from a neurodevelopmental study in animals.
2008AnimalEFSA Scientific Opinion on the safety of aluminium from dietary intake, EFSA Journal
JECFA used a neurodevelopmental study to establish its aluminium safety guidance, consistent with the endpoint used by EFSA.
RegulatoryJECFA (Joint FAO/WHO Expert Committee on Food Additives) evaluation of aluminium
Where it stands with the regulators
Approved for use in the UK and EU, but safety could not be confirmed by EFSA in a 2020 re-evaluation
- Legal basis
- UK assimilated EU Regulation 1333/2008 (Annex II); specifications under Commission Regulation (EU) No 231/2012
- Permitted foods
- Salt and salt substitutes; Powdered and icing sugar; Dextrose; Dried whey and whey preparations; Sliced cheese (as release agent)
- Maximum levels
- Quantum satis (no fixed numerical maximum; used at the lowest level necessary) in most permitted categories
- Acceptable daily intake (ADI)
- No ADI established. EFSA 2020 re-evaluation concluded safety could not be assessed.
- History
- E555 has been permitted under EU food additive rules since the adoption of Regulation 1333/2008. In 2020 EFSA completed a systematic re-evaluation of both sodium aluminium silicate (E554) and potassium aluminium silicate (E555) and concluded that safety of both additives could not be confirmed due to insufficient toxicological data and concerns that aluminium exposure from their use at permitted levels could far exceed the established TWI of 1mg/kg bw/week. No ban or formal restriction was imposed following this opinion, but EFSA called for additional data. The UK FSA retained the additive on its approved list as assimilated EU law post-Brexit.
Who should be careful
People trying to minimise dietary aluminium intake, including those with impaired kidney function (who excrete aluminium less efficiently) and parents of young children (children have a higher relative exposure per kg of bodyweight). Check the ingredients list of table salt, powdered sugar, and dried dairy products for 'potassium aluminium silicate' or 'E555'.
The honest read
E555 is still legal and in use, but the regulatory picture is genuinely unresolved. EFSA's 2020 review, covering decades of permitted use, reached a formal conclusion that safety could not be confirmed, which is an unusual outcome. The concern is not about a single acute dose but about aluminium accumulation from all dietary sources combined. Whether the tiny amounts from this additive in practice tip people over the tolerable intake depends on their overall diet; but the regulator's own exposure modelling showed that maximum permitted use levels could theoretically far exceed the weekly limit. The data gap is real, and the question is open.
Common questions about potassium aluminium silicate
Is E555 banned in the UK?
No. E555 remains on the UK approved additives list as part of assimilated EU law. However, EFSA's 2020 re-evaluation concluded that its safety could not be confirmed due to insufficient data and concerns about aluminium exposure exceeding safe intake levels. It has not been formally banned or restricted following that review.
Why did EFSA say E555's safety could not be assessed?
EFSA found very limited toxicological data on potassium aluminium silicate itself as a compound, and noted that aluminium exposure at maximum permitted additive use levels could theoretically far exceed the established tolerable weekly intake of 1mg of aluminium per kilogram of bodyweight. Without adequate safety data, the panel could not reach a positive safety conclusion.
What foods contain E555?
E555 is found in table salt and salt substitutes, icing sugar and powdered sugar, dextrose, dried whey products, and sliced processed cheese. It appears on the label as 'potassium aluminium silicate' or 'E555'.
Is E555 vegan?
Yes. Potassium aluminium silicate is a mineral of geological origin with no animal-derived components.
Sources
- EFSA Panel on Food Additives and Flavourings: Re-evaluation of sodium aluminium silicate (E554) and potassium aluminium silicate (E555) as food additives (2020)
- EFSA Scientific Opinion on the safety of aluminium from dietary intake (2008), EFSA Journal
- UK FSA Approved Additives and E Numbers
- Commission Regulation (EU) No 231/2012 laying down specifications for food additives
Last reviewed: 20 June 2026
Related additives
It's the only app that does thisUKJaneK
You Need This AppGmac2005
Best AppGK getting skinny UK App Store reviews
See this on every food you scan
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
NutraSafe Pro · £6.99/month · iPhone and Android