Evolution of methylisothiazolinone sensitization: A Belgian multicentric study from 2014 to 2019

Abstract

Background: In the 2010s an epidemic of allergic contact dermatitis to methylisothiazolinone (MI) occurred in Europe. European authorities banned the use of methylisothiazolinone in leave-on cosmetics in 2017 and limited its use in rinseoff products in 2018. Objectives: To investigate the sensitization rate to MI in Belgium between January 2014 and December 2019, and to assess cosensitizations to octylisothiazolinone (OIT) and benzisothiazolinone (BIT) in MI-sensitized patients. Methods: A retrospective study of patch test results with MI, OIT, and BIT observed in patients attending five Belgian hospitals.Results: Overall, 560 of 10 029 patients (5.58%) had a positive patch test reaction to MI, and its sensitization rate decreased from 7.9% in 2014 to 3.1% in 2019. Rinse-off cosmetics, paints, and detergents were the most prevalent sensitization sources in recent years. Simultaneous reactions readily occurred to OIT, and, surprisingly, and increasingly, also to BIT.Conclusions: Contact allergy to MI in Belgium has reached a pre-epidemic level, reflecting the impact of recent regulatory measures. Leave-on cosmetics, in contrast to rinse-off products, have almost disappeared as sensitization sources in Europe.Paints and detergents also remain problematic. The remarkably high number of patients (co)sensitized to BIT should be a focus of future research.

Patch test results with the European baseline series, 2019/20—Joint European results of the ESSCA and the EBS working groups of the ESCD, and the GEIDAC

“…Again, the putatively different patient selection makes it difficult to interpret these data. Probably, pre‐epidemic levels which have been reported by some groups, 34 but not by others, 35 will not be reached soon, in view of the vast number of MI‐sensitized patients, who might present with other current problems but still be MI‐allergic. MI contact allergy might not be clinically relevant in many cases, as allergen avoidance should be (relatively) easy owing to (i) cosmetic restrictions with a ban in leave‐on cosmetics and a restriction to 15 ppm in leave‐on cosmetics and (ii) classification as CLP/GHS ‘H 317: I A’ contact allergen under REACH regulation in Europe, with a requirement to disclose the presence of MI in all products if this exceeds 1.5 ppm.…”

European patch test results with audit allergens as candidates for inclusion in the European Baseline Series, 2019/20: Joint results of the ESSCAA and the EBSB working groups of the ESCD, and the GEIDACC

“…With the restrictions on the use of MI it is unsurprising that departments have seen a rapid fall in allergy to both MI and MCI/MI 14,15 back to pre‐epidemic levels, or not quite so 16 . Although not permitted in cosmetics, both OIT and BIT were recommended for more routine testing 1 and a statistically significant rise in the prevalence of allergy to BIT, in particular, has been found 15,17 . It seemed probable that this increased prevalence had occurred as a consequence of exposure in domestic cleaning products, detergents, and paints.…”

“…16 Although not permitted in cosmetics, both OIT and BIT were recommended for more routine testing 1 and a statistically significant rise in the prevalence of allergy to BIT, in particular, has been found. 15,17 It seemed probable that this increased prevalence had occurred as a consequence of exposure in domestic cleaning products, detergents, and paints. Notwithstanding co-sensitizations to MI, BIT, and OIT, cross-reactivity might also occur between MI and BIT, and to a greater extent between MI and OIT, 18 the latter also found as a leather-treating agent.…”

Hand dermatitis aggravated by contact allergy to methylisothiazolinone in protective nitrile gloves

“…Finally, we cannot exclude that MI-dependent contact dermatitis was further maintained due to frequent exposure to rinse-off cosmetics or detergents. 5 In our patient, regular changes of new gloves every 3 days lead to a relative improvement, but no clearance, of his hand dermatitis. In practice, clinicians must be aware that, occasionally, protective nitrile gloves might contain isothiazolinones, inherently or by contamination, which might potentially aggravate existing hand dermatitis.…”

“…Although in the present case it concerned nitrile gloves, it has been previously described that some rubber gloves (i.e., natural latex rubber) might not always prevent MI penetration 4 ; however, this particular feature (penetration of MI through nitrile rubber gloves) was not investigated in our case. Finally, we cannot exclude that MI‐dependent contact dermatitis was further maintained due to frequent exposure to rinse‐off cosmetics or detergents 5 . In our patient, regular changes of new gloves every 3 days lead to a relative improvement, but no clearance, of his hand dermatitis.…”