Active Ingredients: Benzoyl Peroxide 5% w/w
Preservatives: Methylparaben 0.5% w/w, Propylparaben 0.05% w/w

Parabens are most common in personal care products that contain significant amounts of water such as shampoos, conditioners, lotions and facial and shower cleansers and scrubs because they discourage the growth of microbes. While the Cosmetic Ingredient Review [link to regulation section] recommends concentration limits for single (up to 0.4%) and total paraben concentrations (up to 0.8%) in a single product, these recommendations do not account for exposure to parabens from several products by a single individual.[3]

Parabens are found in nearly all urine samples from U.S. adults regardless of ethnic, socioeconomic or geographic backgrounds.[4] In one biomonitoring study, adolescents and adult females had higher levels of methylparaben and propylparaben in their urine than did males of similar ages.[5]

A 2004 UK study detected traces of five parabens in the breast tumors of 19 out of 20 women studied.[6] This small study does not prove a causal relationship between parabens and breast cancer, but it is important because it detected the presence of intact parabens—unaltered by the body’s metabolism—which is an indication of the chemical’s ability to penetrate skin and remain in breast tissue. A more recent study found higher levels of one paraben, n-propylparaben, in the axilla quadrant of the breast (the area nearest the underarm).[7] This is the region in which the highest proportion of breast tumors is found, although paraben concentration in the tissue samples was not related to location of breast tumors in individual women.

Parabens are not water soluble and can penetrate the skin. As a result, repeated application of a product or multiple products containing parabens could mean almost continuous exposure.[8] The ubiquity of parabens in personal care products makes this a reasonable scenario. (safecosmetics.org)

Methylparaben doesn’t accumulate in the body. In fact, the body flushes the chemical out pretty quickly. Despite this, many consumers are concerned about the safety of methylparaben. These concerns have increased in light of a claimed link to cancer risk.

The FDA and other researchers are conducting studies to investigate the safety of methylparaben. So far there hasn’t been any conclusive evidence, though there have been cases of individuals who have had negative reactions. While the FDA is reviewing these studies, they haven’t yet come across anything to show that parabens are unsafe for use in cosmetics, foods, or drugs.

The Environmental Working Group (EWG) lists methylparaben as being a low to moderate health hazard. However, the hazard is only in regards to allergic reactions or product usage exceeding the recommended level. The EWG lists methylparaben’s risk of causing cancer and reproductive toxicity at 0 percent.

The Centers for Disease Control (CDC) tested the urine of more than 2,548 participants in a 2005 to 2006 survey. CDC researchers found that most participants had some methylparaben in their urine. They also found that the presence of the chemical didn’t signal a problem on its own.

While studies are still being conducted, currently there is no official precaution against using products with methylparaben. (healthline.com)

Parabens are actually several distinct chemicals with a similar molecular structure. Several are common in a wide array cosmetic and personal care products: ethylparaben, butylparaben, isobutylparaben, isopropylparaben, methylparaben and propylparaben.MORE...
Methylparaben and propylparaben are the most common of these.