Methylisothiazolinone (MIT), a biocide, is pervasively used in cosmetics, shampoos and other personal care items as a preservative. In the last decade researchers are uncovering MIT’s negative side effects, from skin allergies to more serious health adversities. This month, the Archives of Dermatology published a study on reports of adverse effects from MIT in baby wipes (2010;146(8)). A total of four cases in adult patients with severe perianal and perineal allergic contact dermatitis seen at the Mayo Clinic during a six-month period were reported. With patch testing, researchers were able to identify an allergy to methylchloroisothiazolinone (MCI)—another preservative known for its antibacterial and antifungal effects—and MIT, and determined all four patients were using moist toilet paper. The dermatitis resolved after use of the moist toilet paper was discontinued.
More deleterious than an allergic reaction is research linking MIT to damaged nerve tissue. A study in 2002 at the University of Pittsburgh School of Medicine, Pennsylvania, reported brief exposure to MIT is highly toxic to cultured neurons, but not to glia (J Neurosci.2002;22(17):7408-7416). Researchers said, “We also show the toxic actions of this biocide are zinc dependent and require the activation of p44/42 extracellular signal-regulated kinase (ERK) via a 12-lipoxygenase-mediated pathway. The cell death process also involves activation of NADPH oxidase, generation of reactive oxygen species, DNA damage, and overactivation of poly(ADP-ribose) polymerase, all occurring downstream from ERK phosphorylation.” And four years later, results from an additional study out of Pittsburgh suggested a disruption of focal adhesion kinase (FAK)- Src family kinase (SFK) complexes due to SFK inhibition leads to FAK dysfunction, with detrimental effects to immature neurons (JPET. 2006;317(3):1320-29). Prolonged exposure to low levels of MIT and related compounds may have damaging consequences to the developing nervous system.