Preservatives may be used in cosmetics to prevent the growth of harmful bacteria and mold. Parabens and formaldehyde-releasing preservatives are commonly used preservatives in cosmetic and personal care products.
Parabens are not water-soluble and can penetrate the skin. As a result, repeated application of a product or multiple products containing parabens could mean almost continuous exposure.
Formaldehyde-releasing preservatives slowly release formaldehyde which kills bacteria in water-based products. A study determined that longer storage time and higher temperature increase the amount of formaldehyde released from formaldehyde-releasing preservatives and could ultimately lead to more severe health concerns.
Other preservatives are emerging as replacements.
Health Concerns
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. Parabens are potential endocrine disruptors due to their ability to mimic estrogen. In cell studies, parabens have been found to weakly bind to estrogen receptors.
Propylparaben is also a reproductive toxin as it affects the male reproduction system and reduces sperm production and testosterone levels.
Butylparaben, specifically, appears to disrupt the male reproductive system and affect reproductive organs.
Methylparaben and other parabens in personal care products can lead to UV-induced damage to skin cells and disruption of cell proliferation (cell growth rate). Of the parabens, methylparaben is generally of lower concern, because it is less estrogenic.
Ethylparaben is listed as a potential endocrine disruptor by the TEDX Endocrine Disruption Exchange.
Formaldehyde: Formaldehyde is classified as a known human carcinogen by the National Toxicology Program and the International Agency for Research on Cancer.
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.
Diazolydinal urea releases the most formaldehyde of any formaldehyde-releasing preservative.
Imidiazoldinal urea is one of the most common antimicrobial agents used in personal care products and is often combined with parabens.
Quaternium-15 is the most sensitizing of these FRPs and is found in blush, mascara, lotion, and shampoo. A study revealed that about 22.3% of consumers are allergic to quaternium-15.
Bronopol (2-Bromo-2-Nitropropane) is a formaldehyde-releasing preservative. It is listed as a potential endocrine disruptor. It is also very toxic to aquatic life and can cause skin irritation and respiratory irritation.
Isothiazolinones: Studies show that isothiazolinones have caused allergic cosmetic dermatitis in many European countries.
Methylisothiazolinone (MIT) is one of the most predominant contact allergens found in cosmetic products. MIT has also been linked to organ system toxicity and neurotoxicity.
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.