Parabens: A Review of Epidemiology, Structure, Allergenicity, and Hormonal Properties

Allison L. Cashman; Erin M. Warshaw


Dermatitis. 2005;16(2):57-66. 

In This Article

Antimicrobial Spectrum and Microbial Resistance

Parabens have a broad spectrum of activity against yeasts, molds, and bacteria. The antimicrobial activity of parabens increases with increasing alkyl chain length. As a result, they are typically combined to enhance antimicrobial efficacy. Parabens are more effective against fungi than against bacteria; their antibacterial activity is greatest against gram-positive organisms and poorest against Pseudomonas species.[10,26] Enhancement of antimicrobial coverage is achieved by combining parabens with other biocides such as formaldehyde releasers, isothiazolinones, or phenoxyethanol.[1,10,26]

Cladosporium resinae, Pseudomonas aeruginosa, and Burkholderia cepacia have been reported to be resistant to parabens.[27,28,29] Certain microorganisms, such as the gram-negative bacteria Enterobacter cloacae, Acinetobacter, Rhodopseudomona palustris, and Burkholderia cepacia, contain specific enzymes that degrade parabens.[30,31,32,33,34] A recent study showed a para-hydroxybenzoate hydroxylase gene (POBA/PRBA) in Enterobacter cloacae and Enterobacter gergoviae strains.[35] This enzyme catabolizes para-hydroxybenzoic acid to the central intermediate protocatechuate, which is ultimately degraded to form tricarboxylic acid intermediates.

Burkholderia cepacia and Enterobacter cloacae known to degrade parabens have led to systemic infections by resistant organisms. Hutchinson and colleagues reported on six patients with serious infections that were caused by an ultrasound gel contaminated with Burkholderia cepacia.[33] The B. cepacia strain that was isolated from the patients' blood was identical to the isolates in the ultrasound gel and demonstrated the ability to degrade parabens in vitro. Enterobacter cloacae was isolated from the ultrasound gel and also demonstrated the ability to degrade parabens. Other cases of nosocomial infections from paraben-containing products contaminated with Enterobacter have been reported, including an outbreak of E. cloacae sepsis in a newborn unit, traced to contaminated total parenteral nutrition solution;[36] an outbreak of E. cloacae and Pseudomonas aeruginosa, traced to a contaminated vial of dextrose;[37] and cases of gram-negative bacteremia in hemodialysis patients, traced to contaminated drain ports.[38]