Can parabens be added to cosmetics without posing a risk to human health? A systematic review of its toxic effects
Objective: To summarize evidence regarding the toxic potential of administering parabenscontaining cosmetics in humans. Methods: The systematic review followed the methodology proposed in Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA). Electronic searches of the PubMed, Virtual Health Library (BVS), and Science Direct databases were performed between October 1st and 31st, 2018. No language restriction was determined. Original articles reporting observational, in vitro and in silico studies of toxicity caused by parabens in human or human cells were considered for eligibility. Two independent reviewers performed data extraction and assessed the methodological quality and risk of bias of articles by using the Downs & Black Scale. Score levels greater than 70% were assumed to reflect good methodological quality. The Kappa coefficient was calculated. Results: A total of 254 studies were found. Following the eligibility evaluation, 22 studies were included for the qualitative synthesis. The concordance between the reviewers was substantial (Kappa coefficient = 0.650). The meaningful reported outcomes were: high concentrations of parabens in the body; apoptosis damage to sperm DNA; oxidative stress; DNA damage; irritative potential; interference in the control of adipogenesis; estrogenic activity; genotoxicity; necrosis; role in carcinogenesis of breast cancer; harmful effects on human skin when exposed to the sun; stimulation of oncogenes expression; and interference with DNA transcription. Despite most included articles presenting appreciable methodological quality, remarkable limitations were observed and the mechanisms by which parabens exert toxicity on humans remained unclear. Conclusions: The accumulation of parabens in the human organism following repeated cosmetics administration on the skin is noteworthy. However overall, the evidence so far does not make it possible to determine whether, and in what extent, the use of paraben-containing cosmetics can disturb human health. Further investigations are still required for clarifying these issues.