Paraben

Parabens are a class of widely used preservatives in cosmetic and pharmaceutical products. Chemically, they are a series of parahydroxybenzoates or esters of parahydroxybenzoic acid (also known as 4-hydroxybenzoic acid). Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bactericidal and fungicidal properties. They are found in shampoos, commercial moisturizers, shaving gels, personal lubricants, topical/parenteral pharmaceuticals, suntan products, makeup, and toothpaste. They are also used as food preservatives. Parabens are a class of widely used preservatives in cosmetic and pharmaceutical products. Chemically, they are a series of parahydroxybenzoates or esters of parahydroxybenzoic acid (also known as 4-hydroxybenzoic acid). Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bactericidal and fungicidal properties. They are found in shampoos, commercial moisturizers, shaving gels, personal lubricants, topical/parenteral pharmaceuticals, suntan products, makeup, and toothpaste. They are also used as food preservatives. No effective direct links between parabens and cancer have been established. Parabens are active against a broad spectrum of microorganisms. However, their antibacterial mode of action is not well understood. They are thought to act by disrupting membrane transport processes or by inhibiting synthesis of DNA and RNA or of some key enzymes, such as ATPases and phosphotransferases, in some bacterial species. Propylparaben is considered more active against most bacteria than methylparaben. The stronger antibacterial action of propylparaben may be due to its greater solubility in the bacterial membrane, which may allow it to reach cytoplasmic targets in greater concentrations. However, since a majority of the studies on the mechanism of action of parabens suggest that their antibacterial action is linked to the membrane, it is possible that its greater lipid solubility disrupts the lipid bilayer, thereby interfering with bacterial membrane transport processes and perhaps causing the leakage of intracellular constituents. Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216), butylparaben and heptylparaben (E209). Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. The general chemical structure of a paraben is shown at the top right of this page, where R symbolizes an alkyl group such as methyl, ethyl, propyl or butyl. All commercially used parabens are synthetically produced, although some are identical to those found in nature. They are produced by the esterification of para-hydroxybenzoic acid with the appropriate alcohol, such as methanol, ethanol, or n-propanol. para-Hydroxybenzoic acid is in turn produced industrially from a modification of the Kolbe-Schmitt reaction, using potassium phenoxide and carbon dioxide. Most of the available paraben toxicity data are from single-exposure studies, meaning one type of paraben in one type of product. According to paraben research this is relatively safe, posing only a negligible risk to the endocrine system. However, since many types of parabens in many types of products are used commonly, further assessment of the additive and cumulative risk of multiple paraben exposure from daily use of multiple cosmetic and/or personal care products is needed. FDA states that they have no information that use of parabens in cosmetics has any effect on health. They continue to consider certain questions and evaluate data about parabens' possible health effects. Parabens are, for the most part, non-irritating and non-sensitizing. Among people with contact dermatitis or eczema, less than 3% of patients were found to have a sensitivity to parabens. At least one case has been reported of an allergic reaction to parabens. The American Cancer Society mentioned a 2004 study that found parabens in the breast tissue of mastectomy patients but did not find parabens to be a cause of the cancers. Michael Thun of ACS stated that the effects of parabens would be miniscule compared to other risks 'such as taking hormones after menopause and being overweight'. A 2005 review concluded 'it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer' and that 'worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring endocrine active chemicals in the diet such as the phytoestrogen daidzein.' Animal experiments have shown that parabens have weak estrogenic activity, acting as xenoestrogens. In an in vivo study, the effect of butylparaben was determined to be about 1/100,000th that of estradiol, and was only observed at a dose level around 25,000 times higher than the level typically used to preserve products. The study also found that the in vivo estrogenic activity of parabens is reduced by about three orders of magnitude compared to in vitro activity.