Scientific Article: Clean Beauty by Dr. Macrene

Clean Beauty is a multi-part series defining and addressing toxic exposure from skincare, environmental effects of manufacturing practices and packaging, and ethical concerns surrounding animal or human-derived ingredients.

Part 1: Defining Clean Beauty

Consumers have become increasingly concerned about toxic exposure from skincare, environmental effects of manufacturing practices and packaging, and ethical concerns surrounding animal or human- derived ingredients. There is evidence indicating that topical agents may result in local and systemic reactions and carcinogenicity from toxic exposures, that certain ingredients are manufactured with inhumane practices, that plastic packaging may leech harmful chemicals into your skin and the environment, and that animal or human byproducts may be hidden in your skincare. As a result, there is a growing demand for greater transparency of ingredient usage and manufacturing practices and for the elimination of potentially harmful ingredients or packaging.

This article defines the categories of skincare ingredients, manufacturing, and packaging that are demonstrated to be harmful to the health of humans, animals and/or the environment or that raise ethical concerns.


The definition of clean beauty de facto commands the designation of unclean ingredients or packaging components with a rationale for their exclusion. Skincare ingredients, manufacturing practices or packaging components may be classified by chemical class, adverse effects, environmental harm and ethical concerns. The banning of unclean ingredients may be due to direct or indirect toxicity, such as carcinogenicity, sensitization, such as allergic contact dermatitis, environmental effects, such as marine ecosystem disruption, or ethical concerns, such as manufacture by underage children or use of animal or human-derived byproducts. 


The first focus of this article to the classification of unclean ingredients to be eliminated from skincare. While they may and should be categorized by their chemical name or class, it is far more informative to group according to their adverse effects first on human health, though subsequent parts of this work will focus on adverse environmental effects, ethical concerns, and the use of animal and human byproducts.

I. Adverse Effects on Human Health


Cancer-causing ingredients, known as carcinogens, may interrupt normal cell function in a variety of ways. The one aspect all cancer cells have in common is uncontrolled reproduction. The unbridled cell cycle results in the proliferation of cancer cells that accumulate in tumor formation, and with additional changes to the genetic material of cancer cells, they may acquire the ability to metastasize or spread.

The mechanism of action of carcinogens varies widely from direct mutagens that enter the nucleus of the cell and alter the DNA resulting in loss of normal cell function and controls to action on the receptors of cells causing downstream effects on hormones and cellular proliferation. One example of the latter are the so-called hormone disruptors; these are ingredients that either mimic hormones by binding to hormone receptors or that indirectly result in the upregulation of hormone secretion, ultimately causing increased cancer risk (Smith et al 2015).

Smith MT, Guyton KZ, Gibbons CF, et al. Key Characteristics of Carcinogens as a Basis for Organizing Data on Mechanisms of Carcinogenesis. Environ Health Perspect. 2016;124(6):713‐721. doi:10.1289/ehp.1509912

In Clean Beauty, Part I, the first class of carcinogens, the Hormone Disruptors are covered.

Sub-Category 1: HORMONE

Hormone disruptors are ingredients that mimic hormones, bind to hormone receptors and interfere or “disrupt” normal hormonal regulation. As a result, cells are overstimulated and cancer is promoted in target tissues, such as breast or uterus, that possess hormone receptors.



BHA and BHT are SPA preservatives employed in skincare which have been implicated as carcinogens in skin (Sato et al 1987). BHA has been shown to increase estrogen secretion (Yang et al 2018).

Sato H, Takahashi M, Furukawa F, et al. Initiating potential of 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (AF-2), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and 3,3‘,4‘,5,7-pentahydroxyflavone (quercetin) in two-stage mouse skin carcinogenesis. Cancer Lett. 1987;38(1-2):49‐56. doi:10.1016/0304-3835(87)90199-6

Xiaoxi Yang, Wenting Song, Na Liu, Zhengdong Sun, Ruirui Liu, Qian S. Liu, Qunfang Zhou, and Guibin Jiang. Synthetic Phenolic Antioxidants Cause Perturbation in Steroidogenesis in Vitro and in Vivo. Environmental Science & Technology 2018 52 (2), 850-858 DOI: 10.1021/acs.est.7b05057.



The parabens are used as preservatives in cosmetic products. The estrogenic effects of parabens have been demonstrated and the association with breast, uterine and prostate cancer reviewed by the author (Alexiades 2008; Karpuzoglue et al 2013).

Alexiades-Armenakas M. Parabens toxicity to skin and other organs. J Drugs Dermatol. 2008;7(1):77‐78.

Karpuzoglu E, Holladay SD, Gogal RM Jr. Parabens: potential impact of low-affinity estrogen receptor binding chemicals on human health. J Toxicol Environ Health B Crit Rev. 2013;16(5):321‐335. doi:10.1080/10937404.2013.809252.


Phthalates are used to make plastics flexible and are well established hormone disruptors. While they may appear on product ingredient labels, they may also be hidden under the term “fragrance.” They have been demonstrated to have adverse effects on male and female reproduction, breast development and cancer, prostate cancer, neuroendocrinology, thyroid, metabolism and obesity, and cardiovascular endocrinology (Diamanti-Kandarakis et al 2009).

Diamanti-Kandarakis E, Bourguignon JP, Giudice LC, et al. Endocrine-disrupting chemicals: an Endocrine Society scientific statement. Endocr Rev. 2009;30(4):293‐342. doi:10.1210/er.2009-0002.



Chemical sunscreens exert hormone disrupting effects on estrogens, androgens, thyroid hormones and progesterone (Wang et al 2016). Adverse effects on neurohormones have been extensively documented (Ruszkiewicz et al 2017).

Wang J, Pan L, Wu S, et al. Recent Advances on Endocrine Disrupting Effects of UV Filters. Int J Environ Res Public Health. 2016;13(8):782. Published 2016 Aug 3. doi:10.3390/ijerph13080782

Ruszkiewicz JA, Pinkas A, Ferrer B, Peres TV, Tsatsakis A, Aschner M. Neurotoxic effect of active ingredients in sunscreen products, a contemporary review. Toxicol Rep. 2017;4:245‐259. Published 2017 May 27. doi:10.1016/j.toxrep.2017.05.006.


Bisphenols were banned as ingredients in cosmetic formulations in 2006, but are used as a coating material in plastic packaging, such as plastic bottles, tubes and aerosols, where it serves as an anti-corrosive. BPs have been shown to leach into the plastic container’s contents resulting in widespread human exposure (Gao et al 2015). The estrogen-mimicking effects of BPs have been established to lead to cancer of the breast, ovary and prostate (Gao et al 2015). For this reason, plastic containers may release these carcinogenic ingredients into skincare. Many plastic manufacturers have skirted the toxicity of bisphenol A (BPA) and labeling their plastic “BPA-free” by substituting with alternate bisphenols such as bisphenol S (BPS) which are likely just as toxic (Bilbrey 2014).

Gao H, Yang BJ, Li N, et al. Bisphenol A and hormone-associated cancers: current progress and perspectives. Medicine (Baltimore). 2015;94(1):e211. doi:10.1097/MD.0000000000000211

Bilbrey J. BPA-Free Plastic Containers May Be Just as Hazardous. Scientific American, August 11, 2014. accessed June 12, 2020.


Triclosan is a broad-spectrum antimicrobial frequently used in personal care products that has been shown in multiple studies to disrupt hormonal systems (Weatherly et al 2017). While banned from soap products in 2016, triclosan continues to be used in hand sanitizer, toothpaste, and mouthwash.

Weatherly LM, Gosse JA. Triclosan exposure, transformation, and human health effects. J Toxicol Environ Health B Crit Rev. 2017;20(8):447‐469. doi:10.1080/10937404.2017.1399306


In order to eliminate the hormone disruptor carcinogens aforementioned and to qualify as Clean Beauty, the following first three criteria as defined in Part I must be met by the product:

  • not contain the carcinogenic ingredients listed above on their ingredient listing
  • be fragrance-free
  • not be packaged in plastic, but rather in glass containers

Summary of Part 1

In this first part of my series on Defining Clean Beauty, I have defined the criteria for clean beauty and for unclean ingredients and practices. This first part commenced with a focus on cosmetic ingredients that are carcinogens. The first sub-category discussed are the hormone disruptors, whose mechanisms of action have been defined and the research demonstrating their link to cancers cited. In order to qualify as clean beauty, the product must not contain the carcinogenic ingredients on their ingredient list; must be fragrance-free; and must not be packaged in plastic, but rather in glass. In the absence of these three criteria, the product may not be considered clean beauty. In the next part, we will cover the next cancer-causing ingredient classes, followed by allergenic and sensitizing ingredients that cause dermatitis, and ingredients associated with other forms of toxicity.

Part 2: The second class of carcinogens: DNA mutagens

In Part II, the second class of carcinogens in skincare and cosmetics, the direct DNA mutagens are introduced and covered. The first sub- group of mutagens are the ethylene oxide derivatives.


Direct DNA mutagens are compounds that penetrate the nucleus and cause direct damage to the DNA of cells. This section will classify mutagens found in skincare and cosmetics.


Ethylene oxide is a compound used to manufacture chemical derivatives in a process termed “ethoxylation” that serves as the basis for consumer goods around the globe. The mutagenicity and carcinogenicity of ethylene oxide is attributed to direct reaction with DNA and formation of multiple 2-hydroxyethyl (HE) DNA adducts.

Most ethylene oxide produced worldwide is used in the manufacture of ethylene glycols. Derivatives of ethylene oxide include diethylene glycol, triethylene glycol, poly(ethylene) glycols, ethylene glycol ethers, ethanol-amines, and ethoxylation products of fatty alcohols, fatty amines, alkyl phenols, cellulose and poly(propylene) glycol. Ethylene oxide is used in the production of PEGs, ceteareths and polysorbates. A significant concern is the contamination of the ethoxylation reaction with 1, 4-dioxane, another direct mutagen.

IARC Working Group on the Evaluation of Carcinogenic Risk to Humans. Chemical Agents and Related Occupations. Lyon (FR): International Agency for Research on Cancer; 2012. (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 100F.) ETHYLENE OXIDE. Available from:

Occupational Safety and Health Administration (2005). Regulatory Review of the Occupational Safety and Health Administration’s Ethylene Oxide Standard (29 CFR 1910.1047), Washington DC

Devanney MT (2010). CEH Marketing Research Report – Ethylene Oxide (Abstract). Zürich: SRI Consulting.

The International Agency for Research on Cancer classifies ethylene oxide into group 1, meaning it is a proven carcinogen. The Environmental Protection Agency classified ethylene oxide as a human carcinogen in December 2016. Studies of workers show that their exposures to ethylene oxide are associated with an increased risk of cancers of the white blood cells and of breast cancer in females.

IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Lyon: International Agency for Research on Cancer. 1999. ISBN 978-92-832-1297-3. Archived from the original on 3 March 2016. Retrieved 28 June 2007.

i. PEGs

Most ethylene oxide is used for synthesis of polyethylene glycols (PEGs) which accounts for up to 75% of global consumption. Over 1000 PEGs are on the International Nomenclature of Cosmetic Ingredients (INCI) database.

PEGs are the products of ethylene oxide and water. Since many PEG types are hydrophilic (water-loving), they are used as penetration enhancers in topical dermatological preparations. PEGs are used in cosmetic products as surfactants, emulsifiers, cleansing agents, humectants, and skin conditioners.

PEG derivatives include:

a. PEG ethers (e.g. laureths, ceteths, ceteareths, oleths)

b. PEG ethers of glyceryl cocoates

c. PEG fatty acids (e.g. PEG laurates, dilaurates, stearates, and distearates)

d. PEG castor oils

e. PEG amine ethers (PEG cocamines)

f. PEG propylene glycols

g. other derivates (e.g., PEG soy sterols and PEG beeswax)

PEGs and PEG derivatives, while generally regulated as safe for use in cosmetics, may be contaminated with ethylene oxides and 1,4-dioxane, known mutagens, which must be completely removed prior to mixing in cosmetic formulations. Thus, assessment studies for each chemical mixture are required in each instance for evaluation of their safety in cosmetic use.

Jang HJ, Shin CY, Kim KB. Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use. Toxicol Res. 2015;31(2):105-136. doi:10.5487/TR.2015.31.2.105.


The ceteareths are synthetic compounds used in skincare that are synthesized through ethoxylation (as aforementioned the chemical reaction in which ethylene oxide is added to a substrate). To generate ceteareths, two substrates, cetyl alcohol and stearyl alcohol, which are both derived from coconut oil, are used. The ceteareth number (for example, ceteareth-20) indicates the number of repeating ethylene oxide units in the molecule. Currently, there are 32 different types of ceteareths.

Ceteareth-20 is a surfactant and an emulsifier in cosmetics and personal care products, including moisturizers, conditioners, cleansers, and sunscreens.

The concerns regarding ceteareths include the presence of the mutagen ethylene oxide and the process of ethoxylation, which may lead to contamination with 1,4-dioxane, also a mutagen. 1,4-dioxane possesses the additional dangerous property of readily penetrating into the skin. It is linked with skin allergies and with potential cancers. The levels of 1,4-dioxane found in many personal care products are reported at 1000 times in excess of levels shown to cause cancer in animal studies.


Polysorbates 20 and 80 (Tween 20 and Tween 80) are used as surfactants and emulsifiers in cosmetics. They prevent surface adsorption and serve as stabilizers against protein aggregation. They are often used in cosmetics to solubilize essential oils into water-based products.

Polysorbates are oily liquids that are made from the substrate sorbitol, which is treated with ethylene oxide. The polysorbate number refers the number of ethylene oxide moieties: for example, polysorbate-20 is comprised of 20 parts ethylene oxide to 1 part sorbitol. As with other ethoxylated compounds, there is the risk of ethylene oxide and 1,4-dioxane contamination, both of which are known carcinogens.

Polysorbates are found in facial cleanser, body wash, toners, and moisturizers. Interestingly, they are used even in purported “natural” and “organic” product lines.

Kerwin BA. Polysorbates 20 and 80 used in the formulation of protein biotherapeutics: structure and degradation pathways. J Pharm Sci. 2008;97(8):2924-2935. doi:10.1002/jps.21190


In order to eliminate the direct DNA mutagens and carcinogens and to qualify as Clean Beauty, the following must be absent from the product:

  1. PEGs
  2. Ceteareths
  3. Polysorbates

Summary of Part 2

In this second part of my series on Defining Clean Beauty, I have defined the criteria for clean beauty and for unclean ingredients and practices. The first part commenced with an overview and classification of unclean ingredients. The first sub-category discussed are the hormone disruptors, whose mechanisms of action have been defined and the research demonstrating their link to cancers cited. The second sub-category are the direct DNA mutagens and include ethylene oxide derivatives. Ethylene oxide and its byproduct during ethoxylation reactions, 1,4-dioxane, directly interact with DNA causing damage, called mutations, that result in cancer formation. Ethoxylated compounds to be eliminated from skincare include the PEGs, ceteareths and polysorbates. Ethylene oxide is classified as a class I carcinogen and shown to increase the risk of cancer of the white blood cells and of the breast.