Can patch testing with methylchloroisothiazolinone/methylisothiazolinone be optimized using a new diagnostic mix?

The share of contact allergy to MCI/MI 0.215% aq., MCI/MI 0.02% aq., and MI 0.2% aq. varied in the test centers between 7.9% and 25.9%, 3.2% and 10.3%, and 5.8% and 12.3%, respectively. MCI/MI 0.215% aq. detected significantly more patch‐test positive individuals than both MCI/MI 0.02% aq. (P < .001) and MI 0.2% aq. (P < .001), as well as either one of MCI/MI and MI (P < .001). In the patients only reacting to MCI/MI 0.215% aq., 57.7% were recorded as having a dermatitis that was explained or aggravated by exposure to either MCI/MI or MI.