Contact sensitization to 5‐chloro‐2‐methyl‐4‐isothiazolin‐3‐one and 2‐methyl‐4‐isothiazolin‐3‐one (MCI/MI)

Abstract

The frequency of positive reactions to 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (MCI/MI) were studied at 22 European contact dermatitis clinics over a period of 1 year. A total of 4713 patients participated. All the patients were patch tested with nickel sulphate, formaldehyde, paraben-mix, and MCI/MI. 19.4% of the patients had positive patch tests to nickel, making this the most common allergen. 3% of the patients reacted to 100 ppm MCI/MI, while 2.6% reacted to formaldehyde and 1.1% to parabens. There was great variation in the frequency of MCI/MI sensitivity among the 22 centres. MCI/MI contact allergy was most common among women and in patients with facial dermatitis, while it was rarely seen in patients with dermatitis on the lower legs. There were no fluctuations in the number of positive patch tests to MCI/MI on a monthly basis when the results from all centres were combined. 117 of the 141 MCI/MI sensitized patients included in the study were retested. 88% had positive patch tests when retested. 101 of the MCI/MI-sensitive patients participated in a double-blind, placebo-controlled product use test. This test showed that 31% of the MCI/MI-sensitive patients had a positive reaction to a MCI/MI-preserved product. Only a few patients reacted to a control product. It is concluded that the preservative MCI/MI is an important new contact allergen.

An update of the risk assessment for methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) with focus on rinse‐off products

“…There is a negative correlation with leg dermatitis (54). The morphology of MCI/MI allergy is that of a typical contact dermatitis but may be patchy and mimic seborrheic dermatitis.…”

An Approach to Predictive Testing of Contact Sensitizers in vitro by Monitoring Their Influence on Endocytotic Mechanisms

“…Strong sensitizers like DNFB [18] and Kathon CG [19] were compared to the weaker but common aller gens formaldehyde [20],NiSO4 [21] and K2Cr20 7 [22], ve ry infrequent sensitizers like phenoxyethanol [22][23][24] and methyl-4-OH-benzoate (methyl paraben) [25] as well as to irritants (SLS, benzoic acid), activating substances (PMA, Con A) and untreated or solvent treated cells used as con trol.…”

Adhesion Molecules in the Nickel Allergic Reaction

“…Nickel is the leading cause of metal-induced contact sen sitivity, emerging as the most common allergen in a Europe an multiccnter survey in which 19.4% of the patients had a positive skin test for nickel [1], 16.7% of female subjects in Toronto, Canada, are sensitized to nickel [2]. Nickel allergy is seen to manifest itself clinically in the form o f contact dermatitis.…”