They prevalence of contact allergy to the preservative methylisothiazolinone increased in Western Canada between 2008 and 2015, peaking at 15.29%—a finding researchers say supports ongoing efforts to monitor and regulate the ingredient.
“We were well aware of methylisothiazolinone or MI as aethylisothiazolinone or MI as a problematic allergen, especially after 2013 when it was recognized as Allergen of the Year by the north American Contact Dermatitis Group,” said Dr. Jessica Guy, lead author of the paper, which was published in the Journal of Cutaneous Medicine and Surgery(May/June 2017; 21(3):207–210).
Dr. Guy (née Wilford) is a 5th-year resident in the Department of Dermatology and Skin Science at the university of British Columbia, Vancouver.
As the more commonly used preservatives such as the formaldehyde-releasers and the parabens began to have negative connotation in the minds of the general public, or data from patch testing raised concerns about them, industry looked to find alternative preservatives that could be used instead, said Dr. Guy.
“That led to the really prevalent use of MCI (methylchloroisothiazolinone) and MI. At the time when [the combination of] MCI and MI were found to be a strong sensitizer, based on initial studies in guinea pigs it was thought that the methylchloralisothiazolinone or the MCI portion was the stronger sensitizer. That led to the use of MI alone as a preservative.” unfortunately, MI also turned out to be a strong sensitizer, she said.
Evidence growing worldwide
Dr. Guy and senior author Dr. Gillian de Gannes were spurred to look at their own clinical data on MI and MCI contact allergy by reports around the world of rising prevalence of MI contact allergy, as well as MCI contact allergy. This included clinical findings published by Dr. Melinda Gooderham in 2015 (Dermatitis July-Aug. 2015; 26(4):166-169).
“That was the main impetus for us to then look at our clinic data and see if we could find a similar pattern, especially from 2013-onward, after we added the 2,000 parts per million MI to our screening series,” said Dr. Guy. She explained that prior to 2013, the contact allergy screen contained MCI and MI in a 3-to-1 ratio at 100 parts per million, which may have led to some false negatives compared to the more sensitive tests of MI at 2,000 parts per million, and the MCI/MI combination at 200 parts per million adopted in 2013.
2,177 patch tests reviewed
A chart review found a total of 104 patients tested positive for MCI/MI or MI alone out of 2,177 total patients patch tested for the preservatives at a single community dermatology clinic in Vancouver from Jan. 2008 to Apr. 2015.
Overall, positive results increased over the study period. They peaked in 2015, with 9.41% testing positive for MCI/MI, 12.94% for MI, and 15.29% for either in that year.
The initial positive patch testing prevalence for MI at 2,000 parts per million was 6.6% when it was introduced in 2013. This rose to 10.1% in 2014, and 12.9% in 2015.
“Looking at our own data from 2013 to 2015, we had 71 patients who reacted to MCI/MI and/or MI,” said Dr. Guy. of those 71 patients, 31 reacted only to MI but not MCI, she said.
“That shows 43.7 per cent of the patients who were, in fact, sensitized to MI would have been missed and had a false negative result if they had only been screened for the earlier 100 parts per million MCI/MI allergen,” said Dr. Guy.
This paper's findings are concordant with those published by the north American Contact Dermatitis Group, said Dr. Guy (Zirwas MJ, hamann D, Warshaw eM, et al: epidemic of isothiazolinone allergy in north America: Prevalence data from the north American Contact Dermatitis Group 2013-2014. Dermatitis 2017 May/Jun; 28(3):204-209). That paper looked at MCI and MI contact allergy prevalence in the 2013 to 2014 period, said Dr. Guy, and 10.7% of the patients were positive to MI contact allergy, compared to 9.0% in the 2013 to 2015 period covered by the paper written by Drs. Guy and de Gannes.
“It just reinforces that this is an increasing allergy-causing sensitization in all kinds of personal products that people are exposed to,” Dr. Guy said.
Family physicians and dermatologists who see patients with dermatitis, particularly when contact dermatitis is being considered and patch testing is available, should definitely consider screening for MI and MCI/MI, Dr. Guy said.
Top 10 list of allergens changing
So prevalent have contact allergies to MI and MCI become that they have pushed other common contact allergens out of the north American Contact Dermatitis Group top 10 list, she said.
“In the last publication this year showing the data from 2013 to 2014, methylisothiazolinone went from being not on the list to now being number three. It has become a very significant allergen.”
MCI/MI has also entered the list at number 10, displacing quaternium15, a formaldehyde-releasing preservative. In fact, other than formaldehyde itself, MI and MCI/MI are the only preservatives remaining on the north American Contact Dermatitis Group’s top 10 list.
Regulation of MCI/MI and MI
Health Canada is moving to more closely regulate MI and MCI/MI, said Dr. Guy, noting that currently MCI may not be used by itself, and the MCI/MI combination may not be used in leave-on products or in rinse-off products targeted for children under the age of three years. In rinse-off products for adults, MCI/MI is restricted to 0.0015% of the make up of the product, or 15 parts per million, she said.
However, health Canada does not regulate either preservative in industrial products, only in personal care products. In the population sample of this study, mechanics were represented more than any other occupation, Dr. Guy said.
“Once [individuals] are sensitized, they can react to [these preservatives] in their personal care products—things like shampoos, soaps, creams, lotions, personal wipes—but also in industry or other uses where they are contacting industrial products,” she said.
Dr. Guy noted that there have been cases where patients have reacted to interior house paint containing MCI or MI, causing the patient to develop generalized contact dermatitis. Some have had to leave their home for up to six months while the preservatives offgassed from the paint.
Originally published in The Chronicle of Skin & Allergy (Oct./Nov. 2017;23(7):page 1,18)