Parabens are esters of p-hydroxybenzoïque acid used as preservatives in thousands of cosmetic, pharmaceutical and foodstuff products (adhesives, bandages, nasal drops, suppositories, food additives, etc…). There are six parabens of which the most used are: methylparaben , ethylparaben , butylparaben and propylparaben .
Certain parabens are naturally present in plants and fruits such as grapefruit pips, wine, green tea but almost all those that are used commercially for their bactericidal and fungicidal properties are synthetic.
Studies on laboratory animals have shown that parabens are quickly absorbed by the mouth or the skin. Although many absorbed parabens are metabolized and excreted by the urine, some remain unmodified and accumulate in the fatty fabrics of the body, like other lipophilic pollutants.
These preservatives are dangerous because once absorbed, they behave like estrogens, i.e. they mimic female hormones while sticking to the receivers of estrogen of the cells of the organism. The estrogenic activity of the parabens was initially announced in 1998. Since that time, several studies proved that the parabens bind themselves to the receivers of oestrogen, causing adverse effects. Thus, the subcutaneous administration of methylparaben in the mouse resulted in developing an adenocarcinomist of the breast. Another in vivo study in 2005 concluded that the use of propylparaben and butyparaben on laboratory animals caused the modification of the reproductive function of the male of which the inhibition of the spermatogenesis.
A “famous” study going back to 2004 and done by Doctor Philippa Darbre showed the accumulation of parabens in cancerous tissue of the breast of human origin (described in the Journal of Applied Toxicology v. 24, i.1, January 1, 04, United Kingdom). On 20 cancerous tumours of the breast observed, 18 comprised parabens. This study was disputed mainly for two reasons: sampling was too small and the methylparaben, the majority component, is the one that has the weakest oestrogenic action of the entire group of parabens. Other studies were done but in the saga of parabens there is the impression practically that with each study pointing towards the link parabens/breast cancer one or more anti-studies correspond. The question of these preservatives is not settled yet and it is not I who will do it.
It is interesting to note that among the parabens detected in human tissues, methylparaben is the one which is there in the greatest quantity reflecting at the same time a broader use in the products for human consumption as well as a strong capacity with being absorbed and being accumulated in the body. As the parabens are used in a variety of dermato-cosmetic products in the areas of the armpit and the breast, it was also suggested that the frequency of their application, in fact in these zones, influences and supports the appearance of breast cancer.
Finally, to conclude, no study has established a direct link and out of any doubt between parabens and breast cancer, but what research has shown without any doubt is that the parabens are hormonal disruptors and that they cause, like the innumerable xenestrogens (environmental estrogens present in domestic products, pesticides, plastics, etc…  , ], a hormonal imbalance . This information is alarming when it is known that the hormonal factors are prevalent in breast cancers. 70% of the breast cancers are hormono-dependent  which means that they developed in a situation of hyperestrogeny or of another hormonal imbalance. When this is known, it becomes obvious that it is necessary to give a particular attention to all these factors which increase our risks of cancer and that it is necessary to always keep in mind that there are hormonal disturbers on which one can act ( parabens in cosmetics ) and others on which one has no control. It is up to you to decide if you want products containing 3 to 5 parabens each or to be careful and to choose alternatives without parabens.
The alarm cries of the scientists do not go back to yesterday, Here is what Rachel Carson said already, in 1962, in her book “ Silent spring ”:
“The chemical agents of cancer are embedded in our world in two manners. The first ironically because of man’s desire to have a better and easier life; the second with the production and the sale of chemicals which became a commonly accepted part of our economy and our way of life. ”
Big pharma, Big cosmetica and Big Food industries fed thoroughly by the thirst for profit but also with the blessing of the governments which agree to allow “the small amount of poison” minimize the effects of parabens on human health counting on their weak concentration in the products without taking account of the effects of addition or “cocktail”. The defense-argument of these industries holds owing to the fact that the majority of the studies which tend to show a link between parabens and cancer are done on laboratory animals, in this case on mice and not on humans. What research showed recently is that it is not so much the quantity of the parabens which counts but rather the moment of the exposure. Pregnant women should pay particular attention to these hormonal disruptors .
A study published in 2009 reports about disturbances of the hormonal system among women of very varied ages following the use of products of personal care: premature development of the breasts and menstruation in a young girl of 36 months old after exposure to a hair lotion containing oestrogenic products used by her mother; abnormal genital bleedings and breast cancer in a 93 year old woman after long-term use of a body care containing ethynyloestradiol. 
How much evidence do we need?
On Skin Deep, you will be able to consult certain scientific studies, information concerning the risks which these ingredients present for health as well as their rating between (5 and 6) as a single substance and not in the composition of the products (for example, methylparaben 5, ethylparaben 5, butylparaben 6 and propylparaben 6)  .
Since January 2011 Denmark has prohibited parabens in all the products intended for children.
“ Manufacture, importation, sale or the offering of products containing phthalates, parabens or the alkylphenols are prohibited ” is the text of a new bill in France which has just been adopted by the French National Assembly on May 3, 2011.
I suggest you read the chapter entitled “ Reading the labels ”, because now that the risk that parabens comprise is increasingly known by the public, industry counter-attacks while affixing on the labels or packaging the mention “ Without parabens ” (sometimes even on products which in any event could not have contained some in the manufacturing formula), but which however contains ingredients even more toxic and more dangerous than parabens.
Another worrying aspect is the increased presence of parabens in drugs, especially medicines for children. Read about ” Are There really phthalates and parabens in medication? ” by Adria Vasil.
 ↑ Gillian Deacon, There is Lead in Your Lipstick
Phillips D. Darbre (2009) «Underarm Antiperspirant/Deodorant and Brest Cancer», Brest Cancer Research 11 (Suppl 3): S5