What are Parabens?How do they affect the skin?

A 20year-old young woman has been diagonised as allergic to parabens.She has acne on her face and has been taking treatment to control this.She applies moisturiserand sunsceen.Of late she has developed red rashes,especially around the mouth ,apart from which she has severe itching on her face .Is it because of a medicine called Isoace[not sure about the spelling] which was administered for 6 months?She was asked to apply moisturiser liberally to counter the dryness.She is now really despondent .will her skin become normal?|||Parabens are a group of chemicals widely used as preservatives in the cosmetic and pharmaceutical industries. Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bacteriocidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, cleansing gels, personal lubricants, topical/parenteral pharmaceuticals and toothpaste. They are also used as food additives.





Their efficacy as preservatives, in combination with their low cost, their long history of safe use—at least to the extent that scientific studies have not proven they are harmful—and the unproven efficacy of natural ingredients like grapefruit seed extract (GSE),probably explains why parabens are so commonplace. They are becoming increasingly controversial, however, and some organizations which adhere to the precautionary principle object to their everyday use.





Chemistry


Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216) and butylparaben. Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. The general chemical structure of a paraben is shown at top right, where R symbolizes an alkyl group such as methyl, ethyl, propyl or butyl.





Occurrence


Some parabens are found naturally in plant sources such as methylparaben from the fruit of the blueberry shrub,where it acts as an antimicrobial agent.








Synthesis


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. para-Hydroxybenzoic acid is in turn produced industrially from a modification of the Kolbe-Schmitt reaction, using potassium phenoxide and carbon dioxide.








Toxicology


Parabens are considered to be safe because of their low toxicity profile and their long history of safe use; however, a few recent controversial studies have begun to challenge this view. Studies on the acute, subchronic, and chronic effects in rodents indicate that parabens are practically non-toxic. Parabens are rapidly absorbed, metabolized, and excreted The major metabolites of parabens are p-hydroxybenzoic acid (pHBA), p-hydroxyhippuric acid (M1), p-hydroxybenzoyl glucuronide (M3), and p-carboxyphenylsulfate (M4).





Allergic reactions


In individuals with normal skin, parabens are, for the most part, non-irritating and non-sensitizing. Parabens can, however, cause skin irritation and contact dermatitis in individuals with paraben allergies, a small percentage of the general population