Preservatives

Parabens: Studies demonstrate that at sufficient concentrations, parabens can increase cell proliferation in human breast cancer MCF-7 cells, which are often used as a sensitive measure of estrogenic activity.[6] Parabens are potential endocrine disruptors due to their ability to mimic estrogen.[7] In cell studies, parabens have been found to weakly bind to estrogen receptors.[8]

Propyl paraben is also a reproductive toxin as it affects the male reproduction system and reduces sperm production and testosterone levels.[9][10][11]

Butyl paraben, specifically, appears to disrupt the male reproductive system and affect reproductive organs.[12][13]

Methyl paraben and other parabens in personal care products can lead to UV-induced damage of skin cells and disruption of cell proliferation (cell growth rate).[14][15] Of the parabens, methyl paraben is generally of lower concern, because it is less estrogenic.

Ethyl paraben is listed as a potential endocrine disruptor by the TEDX Endocrine Disruption Exchange.[16][17]

Isobutylparaben exposure in rats has demonstrated increased uterus weight and uterine sensitivity to estrogen in the offspring.[18]

Formaldehyde: Formaldehyde is classified as a known human carcinogen by the National Toxicology Program[19] and the International Agency for Research on Cancer.[20]

Formaldehyde-releasing preservatives: These preservatives release small amounts of formaldehyde over time.

DMDM hydantoin is a formaldehyde-releasing preservative (FRP) used to prevent microbes from growing in water-based products. It can be found in many personal care products.[21]

Diazolydinal urea releases the most formaldehyde of any formaldehyde-releasing preservative.[22]

Imidiazoldinal urea is one of the most common antimicrobial agents used in personal care products and is often combined with parabens.[23]

Quaternium-15 is the most sensitizing of these FRPs and is found in blush, mascara, lotion, and shampoo.[24] A study revealed that about 22.3% of consumers are allergic to quaternium-15.[25]

Bronopol (2-Bromo-2-Nitropropane) is a formaldehyde-releasing preservative. It is listed as a potential endocrine disruptor.[26] It is also very toxic to aquatic life and can cause skin irritation and respiratory irritation.[27][28]

Isothiazolinones: Studies show that isothiazolinones have caused allergic cosmetic dermatitis[29] in many European countries.[30]

Methylisothiazolinone (MIT) is one of the most predominant contact allergens found in cosmetic products.[31] MIT has also been linked to organ system toxicity[32] and neurotoxicity.[33]

Methylchloroisothiazolinones (CMIT/MCI) in a clinical study, researchers found that dermal irritation most commonly occurs in products with CMIT and MIT/CMIT mixtures, but is not as common in products with only MIT.[34][35]

The following preservatives are increasingly used in personal care products. Few studies examine the health effects of these compounds at the levels used in personal care products.

Benzyl benzoate: One study found that benzyl benzoate demonstrated estrogenic responses in a human breast cancer cell line in culture, which indicates the ability of a substance to mimic estrogen.[36] Benzyl Benzoate is a skin and eye irritant and may severely irritate, burn and sting the genitalia and scalp.[37]

Benzyl Alcohol: is used as preservative, solvent and local anesthetic, reported to cause contact urticaria, also known as hives or a skin rash with red, raised, itchy bumps, in some occupational settings.[38] It can be a skin irritant and inhalation of high concentrations may cause central nervous system effects and may cause skin sensitization in repeated or prolonged exposure.[39]

Benzalkonium Chloride: Benzalkonium chloride is linked to occupational asthma.[40] Short-term exposure is corrosive to the eyes, the skin, and the respiratory tract.[41]

Citric Acid: Short-term exposure to citric acid is irritating to the eyes, and skin and the respiratory tract. Long-term (often occupational) exposure may cause erosion of the teeth.[42] It has caused cough in acute inhalation studies of guinea pigs,[43] ataxia, and respiratory depression in mice.[44]

Dehydroacetic Acid: Dehydroacetic acid can lead to seizures in monkeys[45] and severe hemorrhage in multiple organs in rats.[46]

Essential Oils: Essential oils may contain naturally occurring constituents, ingredients such as pulegone or methyleugenol that may be carcinogenic and alter endocrine functioning.[47][48][49]

Methyleugenol (eugenyl methyl ether) can affect multiple endocrine systems[50] and is listed as a possible human carcinogen by the NTP,[51] IARC[52] and on The California Proposition 65.[53]

Grapefruit Seed Extract (GSE): Grapeseed extract is a low concern on its own, but may also be an ineffective preservative. It has been found that sometimes GSE is preserved with other preservatives,[54] which lead to both its efficacy and health concerns: benzethonium chloride,[55][56][57] methylparaben (see parabens) and triclosan (see below).

Lactic Acid: Lactic acid irritates the skin and the respiratory tract, and is corrosive to the eyes and to the digestive tract when swallowed.[58][59]

Levulinic Acid: Is known to be a moderate skin and eye irritant and is harmful when ingested.[60]

Phenoxyethanol: Skin exposure to phenoxyethanol has been linked to allergic reactions ranging from eczema and hives[61] to anaphylaxis.[62] Acute nervous system effects have been seen in infants who have had oral exposure to phenoxyethanol.[63]

Potassium Sorbate: Potassium sorbate may lead to eye irritation[64] and contact dermatitis.[65]

Sodium Dehydroacetate (DHA-S): DHA-S lead to hemorrhage in multiple organs and prolongation of blood coagulation factors in a study of rats.[66]

Sodium Metabisulfite (SMB): Studies have found that inhaled SMB causes may exacerbate asthma symptoms.[67] SMB has also been found to cause dermatitis[68] in occupational settings.[69]

Sorbic acid: Sorbic acid has been associated with skin irritation, contact urticaria, also known as hives or a skin rash with red, raised, itchy bumps, as well as redness of the skin (erythema), abnormal accumulation of fluid (edema), and inflammation of the skin.[70]

Triclocarban: Triclocarban is a potential endocrine disruptor.[71] Studies have found that exposure to triclocarban in personal care products may amplify the effects of endogenous hormones and enhance testosterone.[72] It is also a skin, eye, and respiratory tract irritant.[73]

Triclosan (TSC): There is evidence that triclosan is an endocrine disruptor[74][75] and impacts thyroid function.[76][77] A number of studies indicate that triclosan promotes bacteria that are resistant to both antibiotic medications and antibacterial products.[78][79]Evidence also shows triclosan bioaccumulates and can harm the environment.[80][81]

Vitamin E (tocopherol): One or more animal studies show tumor formation at high doses.[82][83] Dietary supplementation with vitamin E has been shown to significantly increase the risk of prostate cancer among healthy men.[84]

Zinc Pyrithione (Zpt): Studies have found that Zpt induced significant developmental malformations on fish larvae.[85]

Other preservatives: Several other preservatives may be used in personal care products, despite a lack of data on their health effects: anisic acid, salicylic acid, chlorphenism, stearalkonium chloride, sodium salicylate (aspirin), chlorhexidine digluconate, polyaminopropyl biguanide, and neem oil.