Parabens, phthalates, formaldehydes, petroleum, sulfates, oh my! Skin care products—from acne treatments to zinc oxide sunscreen—contain, cumulatively, more than 8,000 ingredients, so how do you decide which to avoid and which to embrace?

Parabens, a group of commonly used chemical preservatives in cosmetics, loom large as some of the most ubiquitous and problematic ingredients. Listed as propylparaben, methylparaben, ethylparaben, or butylparaben, its presence in products “is indicative the company is not doing the best job they can in cleaning up their act, “ says Stacy Malkan, communication director for the Campaign for Safe Cosmetics and the author of Not Just a Pretty Face (New Society Publishers, 2007). If your shampoo, diaper cream, or toothpaste contains parabens, you can safely bet that more suspicious chemicals are lurking.

While the jury is still out on how grave a danger parabens pose, they get a bad rap for several reasons:

Increased risk of breast cancer. The main problem with parabens is that they mimic the hormone estrogen, which can contribute to or even cause breast cancer. Not only did the Centers for Disease Control find parabens present in the urine of virtually all Americans surveyed, but a United Kingdom study discovered parabens in 19 out of 20 breast cancer tumors. What’s more, “a new study shows that methylparaben interferes with Tamoxifen, a drug used to fight cancer, and reverses its suppressant effect,” Malkan says.

No friend to fertility. As an endocrine disruptor, parabens interfere with normal hormone function. A noteworthy study published in the journal Food and Chemistry Toxicology linked parabens to decreased sperm counts in rats. Other studies suggest parabens in products used by pregnant women can contribute to birth defects.

On the wrong side of pretty. A recent study showed parabens may age the skin when the skin is exposed to ultraviolet light.

Many manufacturers seek to minimize the danger of parabens by saying that the amounts found in their products are too small to be significant—“the dose makes the poison” argument. “Yes, doses are low, but there is a cumulative effect,” Malkan counters. Surveys by the Environmental Working Group, a nonprofit watchdog organization, show that the average adult consumer uses nine personal care products each day.

What’s more, Malkan says, the chemicals we put on our skin may be just as dangerous, if not more dangerous than chemicals we put in our mouths. The ingredients can go directly into the bloodstream, thus avoiding the filtering process of the liver. The toxins remain in the tissue, accumulating in the body. Deodorants are particularly worrisome, as they stay on the skin very close to vulnerable breast tissue, says Malkan.

With those kinds of statistics, it seems like choosing paraben-free products would be a no-brainer. But caveat emptor, says Malkan: “Alternatives to parabens, such as quaternium-15, a formaldehyde-releasing preservative, can be equally toxic.” Look for sodium benzoate and polysorbic acid, she says, which have the lowest toxicity rate among preservatives.

To find out more about which companies use parabens and which don’t, check out the Environmental Working Group’s database at http://www.ewg.org/skindeep/.

For a list of paraben-free body care products, click here.