[6] The popularity of butylparaben in these products is due to its low toxicity in humans and its effective antimicrobial properties, in particular those against mold and yeast.

[10] The exact mechanism of how parabens work is unknown but they are proposed to act by inhibiting DNA and RNA synthesis, and enzymes like ATPase and phosphotransferase in some bacterial species.

It has also been suggested that they interfere with membrane transport processes by disrupting the lipid bilayer and possibly causing the leakage of intracellular constituents.

[12][9] In December 2010 the Scientific Committee on Consumer Products (SCCP) of the European Union reported that insufficient data is available to perform risk assessments for butylparaben in humans.

[13] The committee has also stated that it considers the use of butylparaben and propylparaben as preservatives in finished cosmetic products as safe to the consumer, as long as the sum of their individual concentrations does not exceed 0.19%.

[1] in 2020 European Chemicals Agency (ECHA) added Butylparaben to very high concern (SVHC) in the Candidate List for eventual inclusion in Annex XIV REACH in category "Toxic for reproduction".

[13] Butylparaben displayed the most competitive binding to rat estrogen receptors when tested along with methyl, ethyl, and propylparabens.

[1] Mice administered butylparaben at 0.01-1% body weight for ten weeks showed a decrease in serum testosterone concentration and in spermatid counts in the seminiferous tubules.

[1] A review by the National Toxicology Program concluded, "There is no evidence of demonstrable risk for the development of breast cancer caused by the use of paraben-containing underarm cosmetics.