For many years, parabens were considered among those preservatives with low sysemic toxicity, primarily causing allergy reactions, but we have become aware some synthetic chemicals mimic the female hormone estrogen, our understanding of the toxic effects of synthetic and natural substances has changed.
Reserchers from the Department of Biology and Biochemistry, Brunel University, Uxbridge, Middlesex have found alkylhydroxy benzoate preservatives ( namely methyl -, ethyl -, propyl - and butylparaben ) are weakly estrogenic.