Methylparaben is a member of the paraben family, a group of compounds that possess antibacterial and antifungal properties. These agents are esters of para-hydroxybenzoic acid, which is why they’re collectively called parabens. However, in contrast to its cousins, ethylparaben, butylparaben, and propylparaben, methylparaben receives its specific name owing to the fact that its chemical structure contains the methyl alkyl group.
Due to its antimicrobial properties, methylparaben is used extensively as a water-soluble preservative in many foods, beverages, pharmaceuticals, and personal care products. Although it is usually synthesized in a laboratory for this purpose, it is essentially identical in molecular structure to the same compound that occurs in nature. In fact, most plants synthesize para-hydroxybenzoic acid into parabens as a defense mechanism to thwart attacks from bacteria and fungi. Those that are known to produce this substance specifically include wintergreen, birthwort, and blueberries.
Advocates of organic and natural foods and cosmetics have expressed concerns over the use of parabens in consumer products for years, but there is little evidence to warrant it. While it is true that methylparaben is readily absorbed through the skin as well as in the intestinal tract, it is converted back into para-hydroxybenzoic acid and quickly excreted through urine. In fact, the only negative side effects that have been documented are contact dermatitis and skin sensitivity, both occurring with rare frequency and only in reaction to very high concentrations of test material.
There is even less evidence to support the persistent belief that methylparaben is carcinogenic and oestrogenic. Numerous studies involving humans have consistently demonstrated that para-hydroxybenzoic acid is non-toxic. In addition, a great number of plants and fruits contain constituents that exhibit far more oestrogenic activity than methylparaben, including clover, apple, cabbage, potato, carrot, wheat, and scores of others.
In terms of environmental impact, methylparaben is completely and readily biodegradable. As might be expected, it is degraded into para-hydroxybenzoic acid by exposure to water, sunlight, and microscopic organisms in the soil. In addition, the degradation of this substance actually helps to remove toxic phenols from the surrounding environment. This is possible because bacteria belonging to the Enterobacteriaceae family feed off of the carbon molecules in methylparaben, which leaves phenol as a by-product. Another strain of bacterium known as Pseudomonas consume the leftover phenol for energy by breaking the substance down into harmless carbon compounds.
Some of the synthetic alternatives to using methylparaben as a preservative do not share the same positive qualities noted here. For example, thimerosal has been used in vaccines, although it has been eliminated or reduced to very small amounts in most. Thimerosal has been shown to be a neurotoxin and accumulates in the fatty tissue of marine life. Beyond a small potential for skin sensitivity to develop, no detrimental effects have been found from using methylparaben to preserve vaccines or other injection medicines.