Parabens were named nonallergen of the year! It is time that we help consumers understand that the substitutes for parabens are often worse than parabens, and parabens are not as sensitizing as we thought. Preservatives are essential parts of most cosmetics and cosmeceuticals. (I say “most” because many organic products do not have them and consequently have shorter shelf lives.) Without them, products are vulnerable to rapid decomposition and infiltration by bacteria, fungi, and molds. The preservatives that are used in the place of parabens often are sensitizers. What do we tell our patients about the safety of parabens with all of these conflicting reports? This column will focus on current thoughts regarding the safety of parabens used as preservatives. I would love to hear your thoughts.
Background
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Parabens are alkyl esters of p-hydroxybenzoic acid and have been used as a class of preservatives since the late 1920s and early 1930s. Parabens are found naturally in raspberries, blackberries, carrots, and cucumbers and are common ingredients in food and pharmaceuticals. They are still widely used in skin, hair, and body care products, despite the public outcry against them.1-4
There are many kinds of parabens such as butylparaben, isobutylparaben, ethylparaben, methylparaben, propylparaben, isopropylparaben, and benzylparaben, each with its own characteristics.5 Parabens are considered ideal preservative ingredients because they exhibit a broad spectrum of antimicrobial activity, stability over a large pH and temperature range, have no odor, do not change color, and are water soluble enough to yield an effective concentration in a hydrophilic formulation.3 As the alkyl chain length of parabens increases, they become less water soluble and more oil soluble. Parabens penetrate the skin barrier in inverse relation to its ester chain length.6 Often, several parabens will be combined to take advantage of each paraben’s solubility characteristics.
Many patients avoid parabens because of “health risks.” Now other preservatives are being substituted for parabens, even though these ingredients may be less studied or even less safe than parabens. It is important not to lump all parabens together as they each have different characteristics. Methylparaben and propylparaben are the most commonly used parabens in skin care products.7 Combinations of parabens are notably more effective than the use of single parabens.3,8 High concentrations of any type of paraben can cause an irritant reaction on the skin, but those with longer ester chain lengths are more likely to cause irritation.
Methylparaben
The methyl ester of p-hydroxybenzoic acid is found in many skin care products. It is readily absorbed through the skin and gastrointestinal tract. It is quickly hydrolyzed and excreted in the urine and does not accumulate in the body. Studies have shown it is nontoxic, nonirritating, and nonsensitizing. It is not teratogenic, embryotoxic, or carcinogenic. Methylparaben, because of its shorter side chain groups and greater lipophilicity, has been shown to be more readily absorbed by the skin than other paraben chemicals.8,9 It is also on the low order of ingredients provoking acute and chronic toxicity.3