MI belongs to the group of isothiazolinones, which prevents the formation of microorganisms and is cytotoxic.
In 2012, two multicentre studies, comprising 8,680 and 7,874 patients in Belgium and France respectively, showed the rise in contact allergy caused by MI, with a sensitization rate of about 6%, even increasing to 7% in 2013(Eur J Dermatol May-Jun 2015; 25(3): 228–233). In 2015, Europe banned methylchloroisothiazolinone/MI mixture in leave-on cosmetics and MI in Feb. 2017.
All products intended for use by children under the age of three containing MI/MCI were banned in Canada in June 2016 and all other leave-on products containing MI/MCI were banned in Dec. 2016, according to Health Canada. MI is permissible in all cosmetic products at a max concentration of 100 ppm and MI/MCI only in rinse-off products at a max concentration of 15 ppm. Currently, Europe has the same regulations.
“The ban on the use of methylisothiazolinone needed to be extended, with stricter regulations on the use of this agent in rinse-off products,” stated Dr. Professor An Goossens, Leuven, Belgium, at the EADV congress. The current permissible max concentrations “cannot be considered safe for the consumer as far as the induction of contact allergy is concerned.”
In a recent study, published in the journalContact Dermatitis (May 2017; 76(5): 272–279), investigators found clinically relevant MI contact allergy remains prevalent across European countries. Eleven European dermatology departments from eight European countries prospectively collected data between May and Oct. 2015 among consecutive patients who had positive patch test reactions to MI. MI contact allergy was relevant mainly because of exposure to cosmetic products, even when only rinse-off cosmetic products containing MI or MCI/MI were used.
No safe level identified
That MI can be a problem in rinse-off products was also shown in another study (Br J Dermatol July 2015; 173(1):115–122) in which 10 out of 10 MI-allergic subjects developed positive reactions to the soap at 100 ppm and seven out of nine reacted to the 50 ppm soap during 21 days of application. No reactivity was seen to the soap without MI. The investigators of that study concluded, “rinse-off products preserved with 50 ppm MI or more are not safe for consumers. No safe level has yet been identified.”
When patients frequently have skin contact with rinse-off products, such as, for example, hairdressers exposed to hair-care products or nurses to liquid soaps containing MI, then such products become “leave-on products. This clearly demonstrates that the upper limit of 100 ppm for MI concentration in rinse-off products is much too high,” said Dr. Professor Goossens.
“We dermatologists believe that the maximum concentration should not be higher than 15 ppm for rinse-off cosmetic products, because higher MI concentrations do harm people. This maximum concentration has recently been agreed upon in the EU in July 2017, which will be implemented from April 2018 on,” Dr. Professor Goossens reported. Moreover, its inclusion in toys for children below three years of age will be banned.
The issue is not confined to cosmetic products, noted an EADV press release, since there are also problems with MI in many water-based household and other products, such as detergents, paints, glues, air fresheners, or ironing water, which frequently give rise to air-borne (sometimes generalized) allergic reactions in sensitized subjects. The first documented cases of paint-related MI allergy in the United States were recently published in the journalDermatitis (July/Aug. 2017; 28(4): 284–287).
“Although the frequency of MI-allergic cases seem to have decreased recently, in our view, it is important to declare MI, as well as all isothiazolinones, in all products, not only in cosmetics, but also in products such as paints,” said Dr. Professor Goossens.
He noted that in Europe, products will be required to have a warning regarding the sensitization potential of MI if the concentration is 15 ppm, and will be labelled that the product contains MI if the concentration is above 1.5 ppm.