Parabens are a group of the alkyl esters of p-hydroxybenzoic acid and typically include methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben, isopropylparaben, and benzylparaben. Parabens (or their salts) are widely used as preservatives in cosmetics, toiletries, and pharmaceuticals.

Parabens Danger, Parabens Advantage, and Side Effects
Parabens have a low toxicity profile and a long history of use. Testing of parabens has revealed to varying degrees that individual paraben compounds have weakly estrogenic activity in some in vitro screening tests. Reported in vivo effects include increased uterine weight (i.e., butyl-, isobutyl-, and benzylparaben) and male reproductive-tract effects (i.e., butyl- and propylparaben). However, in relation to estrogen as a control during in vivo studies, the parabens with activity are many orders of magnitude less active than estrogen. However, the risk remains that excessive parabens absorption from cosmetic skin care products could have an influence on breast tissue.

Parabens and Breast Cancer
It appears that parabens do have estrogen like activity and hence may influence breast tissue. It remains to be seen whether parabens use increases the risk of breast cancer or perhaps has no practical effect.

Estrogenic activity of p-hydroxybenzoic acid (common metabolite of paraben esters) and methylparaben in human breast cancer cell lines.
J Appl Toxicol. 2005 Jul-Aug;25(4):301-9. Pugazhendhi D, Pope GS, Darbre PD.Division of Cell and Molecular Biology, School of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ, UK.
This paper addresses the question of whether p-hydroxybenzoic acid, the common metabolite of parabens, possesses oestrogenic activity in human breast cancer cell lines. The alkyl esters of p-hydroxybenzoic acid (parabens) are used widely as preservatives in consumer products to which the human population is exposed and have been shown previously to possess oestrogenic activity and to be present in human breast tumour tissue, which is an oestrogen-responsive tissue. Recent work has shown p-hydroxybenzoic acid to give an oestrogenic response in the rodent uterotrophic assay. We report here that p-hydroxybenzoic acid possesses oestrogenic activity in a panel of assays in human breast cancer cell lines. Conclusion: It can be concluded that removal of the ester group from parabens does not abrogate its oestrogenic activity and that p-hydroxybenzoic acid can give estrogenic responses in human breast cancer cells.

Cosmetic free parabens are widely available.

Parabens questions
Q. We would appreciate the doctor's opinion of the use of "methyl and propyl parabens" and propylene glycol in products used on the skin, or other personal care products.
     A. I have not studies parabens in any detail and hence don't have a good understanding of parabens or its various forms.

Physicians Formula Cosmetics files lawsuit against Physician Formulas. Attorneys involved are Kirkland and Ellis.