Purpose of review: The aim of this review was to examine the current outbreak of cases of contact allergy to methylisothiazolinone in Europe, a phenomenon that has also been observed worldwide, despite initial legislative control of the introduction of methylisothiazolinone into the market.
Recent findings: Reported allergic contact reactions are primarily eczematous, most commonly in women over 40 from cosmetic use, but there are reports of noneczematous eruptions such as lichen planus-like or lymphomatoid reactions. Methylisothiazolinone in cosmetic, personal care, for example, wet wipe, and household products are the most common exposure. Occupational exposure is represented by workplace use of hygiene (healthcare) and beauty products (hairdressers, beauticians) together with water-based paints and other aqueous solutions such as cutting fluid.Methylisothiazolinone should be patch tested at a concentration of 2000 ppm (0.2% aqueous) to maximize sensitivity of the test.Notwithstanding the recommendation to discontinue the use of methylisothiazolinone in leave-on cosmetics, studies suggest safer use of concentrations should also be determined for rinse-off products. Legislation to improve labelling of industrial materials is also required.Going forward there is a need for collaboration between the cosmetic industry and interested physicians to break the recurrent cycle of sensitization to preservatives as one is replaced with another to maintain the risk of sensitization at an acceptably low level.
Summary: Methylisothiazolinone is particularly relevant at present as strategies to control the outbreak are yet to be enforced and there is no current evidence of the outbreak abating.