Litholrubine BK
A synthetic red azo dye used to colour the outer rind of hard and semi-hard cheeses. Not found in the edible part of food.
Regulators withdrew the acceptable daily intake in 2010 because the underlying toxicology studies were too thin to stand on. People who react to azo dyes or have aspirin-like sensitivities may experience skin or respiratory reactions.
What is it?
Litholrubine BK is a synthetic monoazo dye that produces a vivid red to carmine colour. It is manufactured as a calcium salt and is practically insoluble in cold water. It is also used industrially in printing inks and plastics, where it is known as Pigment Red 57.
What does it do?
Applied as a surface colourant to the rind of hard and semi-hard cheeses such as Edam and Gouda to give a characteristic red or carmine appearance. The dye sits on the outer wax coating and does not migrate into the cheese itself under normal use.
Where you will see it
Edible rinds of hard and semi-hard cheeses, particularly wax-coated varieties such as red-rinded Edam and Gouda. It appears on the label as 'colour (E180)' or 'Litholrubine BK'.
What the science says
Regulators pulled the acceptable daily intake because the data did not support it
The EU's Scientific Committee on Food originally set a daily intake limit of 0 to 1.5 mg per kilogram of body weight per day. When EFSA re-examined the evidence in 2010, it found that the rat studies underpinning that figure were too limited to identify a reliable no-effect level. JECFA had reached the same conclusion earlier for the same reason. EFSA withdrew the existing limit and declined to set a new one, citing an insufficient toxicological database rather than a proven harm.
EFSA concluded that the existing SCF ADI of 0 to 1.5 mg/kg body weight per day should be withdrawn because the Panel could not identify a suitable NOAEL, LOAEL, or benchmark dose from the available long-term studies.
JECFA was unable to establish an ADI, finding that limited histopathological examinations in two long-term studies in mice and rats did not allow an unequivocal no-effect level to be determined.
Real-world exposure from cheese rind is very low
EFSA estimated that the highest plausible intake from eating cheese rind is around 1700 times lower than the dose at which effects were seen in female rats. Because the dye is applied only to the outer surface and the rind is rarely eaten, the panel considered the practical human exposure to be negligible under current permitted use.
The highest anticipated consumer exposure to Litholrubine BK was estimated to be approximately 1700-fold lower than the identified effect level of 100 mg/kg body weight per day observed in female rats.
Genotoxicity testing returned negative results, but the database is thin
The available in vitro tests did not show mutagenic or chromosome-damaging effects. EFSA noted this as a reassuring finding but also acknowledged that the overall dataset for Litholrubine BK is small, and gaps remain.
Summarised genotoxicity data suggest that Litholrubine BK is not mutagenic or clastogenic in vitro, based on available studies.
Azo dye sensitivity: limited data for this specific dye
As a member of the azo dye family, Litholrubine BK may theoretically trigger reactions in people who are sensitive to azo compounds or who have aspirin-like intolerances. One case of lip inflammation (cheilitis) was documented following cosmetic exposure. EFSA examined the evidence in 2010 and found no well-documented cases of intolerance after oral intake, but the data set was small and no firm conclusion could be drawn.
No well-documented cases of intolerance reactions after oral exposure to Litholrubine BK have been reported. One case report of cheilitis following cosmetic exposure was identified. No conclusion on the induction of hypersensitivity could be drawn from the limited available evidence.
Not permitted outside the EU and UK
Litholrubine BK does not appear on the permitted food colour lists of the United States, Canada, or Australia. No food use authorisation for this dye has been identified in those jurisdictions, meaning food products from those countries will not carry it.
Litholrubine BK (E180) has not been identified as an approved food additive in the United States, Canada, or Australia. No entry for this dye appears in the FDA color additive inventory, Health Canada's List of Permitted Colouring Agents, or the FSANZ food additives schedule.
Where it stands with the regulators
Who should be careful
People with known sensitivity to azo dyes may wish to avoid eating cheese rind coloured with E180. Those with aspirin-like (salicylate) intolerances are sometimes advised to be cautious with azo dyes as a class, though specific clinical evidence for E180 is limited. Look for 'colour (E180)' or 'Litholrubine BK' in the ingredients list on the cheese label.
The honest read
The scientific picture on Litholrubine BK is notably thin for a permitted food additive. Both JECFA (1987) and EFSA (2010) were unable to establish an acceptable daily intake because the long-term animal studies did not generate enough data to identify a reliable no-effect level. That is a data-gap problem rather than a signal of proven harm, but it means regulators are operating without the usual safety anchor. Actual exposure is very low because the dye sits on cheese rind that most people do not eat. In vitro genotoxicity tests returned negative results. The honest position is that the toxicological database is inadequate, real-world exposure is minimal, and the science here is incomplete rather than settled.
Related additives
Common questions
Is E180 banned in the UK?
No. E180 is approved in the UK and EU, restricted to the edible rind of hard and semi-hard cheeses. It is not on the permitted food colour lists in the United States, Canada, or Australia.
Why did regulators withdraw the daily intake limit for E180?
In 2010, EFSA found that the rat studies used to set the original limit were too limited to reliably identify a no-effect dose. The limit was withdrawn not because harm was established, but because the underlying data were insufficient to validate it. JECFA had reached the same conclusion in 1987.
What foods contain E180?
Under UK and EU law, E180 may only be used on the edible rind of hard and semi-hard cheeses, such as red-wax-coated Edam and Gouda. It is not permitted in any other food category. The rind of these cheeses is typically not eaten.
Is E180 vegan?
Litholrubine BK is a synthetic coal-tar-derived dye with no animal ingredients in the dye itself, but it is applied to cheese, which is a dairy product. Whether it is acceptable to vegans depends on the individual's position on cheese rinds.
Sources
- EFSA Scientific Opinion on the re-evaluation of Litholrubine BK (E 180) as a food additive, EFSA Journal 8(5):1586
- EFSA Scientific Opinion on appropriateness of food azo-colours including Litholrubine BK (E 180) for food ingredient labelling, EFSA Journal 8(10):1778
- UK Food Standards Agency: Approved additives and E numbers
- JECFA evaluation of Lithol Rubine BK -- WHO/FAO JECFA additives database
- JECFA evaluation record for Lithol Rubine BK (inchem.org)
- Health Canada: List of Permitted Food Colours (Colouring Agents)
- Food Ingredients First: EFSA Re-evaluates Safety of Litholrubine BK (E180) as a Food Additive
- Dairy Reporter: EFSA finds no major safety concerns with cheese rind dye
- Wikipedia: Lithol Rubine BK
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