Synthetic dyes are a broad group of ingredients that have been chemically manufactured to add vibrant, stable colours to products such as soaps, shampoos and mouthwashes. Many synthetic dyes are derived from non-renewable coal tar or petrochemicals, which contain carcinogens and can be eye, skin and lung irritants. We choose to leave synthetic dyes out of our products.
Synthetic dyes are often referred to as ‘coal tar dyes’, as many are derived from the thick, dark liquid byproduct of coal. ‘Natural dyes’ generally refers to pigments derived from sources such as flowers, minerals, wood, vegetables and some insects. Compounds in synthetic dyes are typically derived from the hydrocarbon benzene, which absorbs bands of light in the ultraviolet spectrum. The addition of substances known as chromophores can shift this absorption band into the visible spectrum, creating different hues.
Common examples of synthetic dyes are ‘Blue 1 Lake’, ‘FD&C Green No. 3’ and ‘Yellow 6 Lake’, which can be found in a wide range of products including food colourings, soft drinks, soaps, cosmetics and toothpastes. The FDA continues to monitor and update a list of colour additives approved for use in the US, along with those restricted and outright banned. A 2012 independent review concluded that all 9 of the synthetic food dyes approved for use in the US raised health concerns, including some of contamination with carcinogens, hypersensitivity reactions and genotoxicity (causing cell damage). Many synthetic pigments are produced with metal salts such as aluminium, and may also contain traces of heavy metals which can be toxic to aquatic wildlife and bioaccumulate when released into waterways. As the science around the safety of synthetic dyes remains contested, we prefer to take the precautionary approach and leave them out of our products.
Other names: FD&C Blue No. 1 Aluminum Lake, D&C Yellow No. 6 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Green No. 3
F.J. Baker F.I.M.L.S., F.I.S.T., R.E. Silverton F.I.M.L.S., L.I. Biol. (1976) Introduction to Medical Laboratory Technology (Fifth Edition). Chapter 17 - Biological Staining - Synthetic Dyes. https://doi.org/10.1016/B978-0-407-00154-1.50021-X
Kobylewski, S., & Jacobson, M. F. (2012). Toxicology of food dyes. International journal of occupational and environmental health, 18(3), 220–246. https://doi.org/10.1179/1077352512Z.00000000034
United States Food & Drug Administration (FDA). Color Additives Status List. https://www.fda.gov/industry/color-additive-inventories/color-additive-status-list