Below are descriptions of two of the ingredients I am trying to avoid or use very minimally. As you can see, there are various health concerns associated with each one and I believe that any small step I can take to limit my exposure to these chemicals is worth it to me.
Parabens are a class 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 bactericidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, personal lubricants, topical/parenteral pharmaceuticals, spray tanning solution and toothpaste. They are also used as food additives.
Their efficacy as preservatives, in combination with their low cost, the long history of their use, and the inefficacy of natural alternatives like grapefruit seed extract, probably explains why parabens are so commonplace. They are becoming increasingly controversial, however, because they have been found in high concentrations in breast cancer tumors.  Parabens have also displayed the ability to weakly mimic estrogen (a hormone known to play a role in the development of breast cancer). No causal link between parabens and cancer has been established, however.
Both Sodium Lauryl Sulfate (SLS) and its close relative Sodium Laureth Sulfate (SLES) are commonly used in many soaps, shampoos, detergents, toothpastes and other products that we expect to “foam up”. Both chemicals are very effective foaming agents, chemically known as surfactants.
In fact, SLES is commonly contaminated with dioxane, a known carcinogen.
A report published in the Journal of The American College of Toxicology in 1983 showed that concentrations as low as 0.5% could cause irritation and concentrations of 10-30% caused skin corrosion and severe irritation.
In the same way as it dissolves the grease on car engines, sodium lauryl sulfate also dissolves the oils on your skin, which can cause a drying effect. It is also well documented that it denatures skin proteins, which causes not only irritation, but also allows environmental contaminants easier access to the lower, sensitive layers of the skin.
Perhaps most worryingly, SLS is also absorbed into the body from skin application. Once it has been absorbed, one of the main effects of sodium lauryl sulfate is to mimic the activity of the hormone Oestrogen. This has many health implications and may be responsible for a variety of health problems from PMS and Menopausal symptoms to dropping male fertility and increasing female cancers such as breast cancer, where oestrogen levels are known to be involved.
More SLS information – http://en.wikipedia.org/wiki/Sodium_lauryl_sulfate
Are you aware of a lot of the ingredients in your beauty products? Is there anything you try to avoid?