A research letter – Has the epidemic of allergic contact dermatitis due to Methylisothiazolinone reached its peak? – written by over a dozen dermatologists based throughout the UK, has just been published in the British Journal of Dermatology, and it includes some interesting data about the collated results of patch testing conducted at various national centres in recent years.
Since 2010, the percentage of patients undergoing patch testing and found to be positive to MI had been steadily increasing in roughly 3% leaps, from 1.67% (2010), to 4.92% (2011), 7.68% (2012) and 11.03% (2013). But 2014 found the first – albeit very modest – reduction, to 10.73%. The researchers add that “the incidence of allergy to MCI/MI appears to have mirrored this plateau effect with it reaching 9.6% in 2014 but still yet to decline”.
Other than the fact that the prevalence of MI and/or MCI/MI allergy is around 10% in patch tested individuals (estimated still to be around 1% of the general population), the letter also tells us that even though the incidence (rate of new diagnoses) may be slowing, the prevalence is of course still rising as people continue to get diagnosed – and many undiagnosed or correctly self-diagnosed will be unaccounted for in the figures.
It is tempting to speculate why this slowdown may have occurred, and you can’t help but suspect that the major adverse publicity about methylisothiazolinone in 2013 – this report from the Telegraph being just one items of coverage – may have deterred some consumers from using products containing MI, as well as given added cause to cosmetics brands to quickly reformulate products ahead of legislation which later came in, banning MI/MCI from leave-on products by April 2016 in the EU.
Further legislation, banning MI from leave-on products by February 2017, has just been approved, can we be hopeful that incidence rates continue to decline?
The use of MI in rinse-off products – permitted at 100 parts per million, with sensitised individuals reacting typically at around 50ppm – means that “a large proportion of the undiagnosed public will suffer from continued episodes of atopic contact dermatitis”, and will of course be of no use to the diagnosed, who will still have to check labels and avoid the ingredient.
This situation may be partly resolved if MI is further restricted to 15ppm in rinse-off, bringing it in line with permitted usage for the MI/MCI mix.
NB: MI allergy patients can access the full article without paying the publishers’ fee, using the PatientAccess scheme. There is still a small fee from the copyright clearing centre but the British Journal of Dermatology waive the fee of the actual paper to patients.