Green S

Picture of Green S

Green S is an Artificial Food Colour

Green S

Green S is a bright green artificial food dye from the triarylmethane dye family. It may also be called Food Green S, Lissamine Green, Wool Green BS, or Acid Green 50.


Triphenylmethane dyes tend to be brightly coloured. Many produce reactions in response to acids or bases. As a result, they are ofter used as pH indicators. Triarylmethane dyes are artificial organic compounds. They are all based on the compound triarylmethane which has the chemical formula (C6H5)3CH. It basically looks like three rings joined by a central hub, as shown:

Picture of Triphenylmethane structure


The chemical formula of Green S is C27H25N2O7S2Na.

Common Uses:

Green S in not allowed in Canada1 or in the United States2. It has been approved for use the the E.U.3 and other countries.

It is used in a range of products, including:

Health Issues / Side Effects:

Studies on the absorption, distribution, metabolism and excretion of Green S have found that Green S is poorly absorbed and mainly excreted unchanged4. There is a lack of data regarding the health effects of Green S. It should probably be noted that many groups associate it with the same health issues and risks attributed to other artificial food colours like Allura Red and Tartrazine.

E Number

The E number of Green S is 142. Other green dyes include Chlorophyll (E number, 140), Chlorophyll-copper complex (E number 141), and Fast Green FCF (E number 143).


Besides being used as a food dye, it is used to stain living cells. It is commonly used in ophthalmology to diagnose problems on the surface of eyes.


  1. Health Canada – List of Permitted Food Colours
  2. Summary of Color Additives for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices
  3. Current EU approved additives and their E Numbers
  4. Scientific Opinion on the re-evaluation of Green S (E 142) as a food
  5. Eye World – The Newsmagazine of the American Society of Cataract and Refractive Surgery
Posted in Colour, Food Additives

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