Patch testing with methylchloroisothiazolinone/methylisothiazolinone 200 ppm aq. detects significantly more contact allergy than 100 ppm. A multicentre study within the European Environmental and Contact Dermatitis Research Group.
BACKGROUND
Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) are the active ingredients in commonly used preservative systems (e.g. Kathon CG(®)). MCI/MI is present in the European baseline patch test series at 100 ppm aq. Since 1986, 200 ppm (dose 0.006 mg/cm(2)) has been used in Sweden without causing skin irritation. Centres in Spain, the United Kingdom and Ireland have also used 200 ppm in their baseline series.


OBJECTIVE
To find the optimal patch test concentration for MCI/MI.


METHODS
MCI/MI 100 ppm aq. and MCI/MI 200 ppm aq. were simultaneously patch tested in 3300 consecutively tested dermatitis patients at eight European patch test clinics and one US patch test clinic. With the Finn Chambers(®) technique (diameter 8 mm), 15 µl was micropipetted on to the filter paper in the chamber. The corresponding volume for Van der Bend(®) chambers was 20 µl, and that for IQ Chambers(®) was 25 µl.


RESULTS
Contact allergy to MCI/MI at 100 and 200 ppm was found in 1.2% and 2.1% of patients, respectively (p < 0.001).


CONCLUSIONS
MCI/MI 200 ppm aq. (dose 0.006 mg/cm(2) ) diagnoses significantly more contact allergy than the presently used concentration of 100 ppm (dose 0.003 mg/cm(2)), without resulting in more adverse reactions. MCI/MI at 200 ppm should therefore be considered for inclusion in the European baseline test series.
Department of Occupational and Environmental Dermatology, Skåne University Hospital, Lund University, SE-205 02, Malmö, Sweden.
Magnus
M
Bruze
Marléne
M
Isaksson
Birgitta
B
Gruvberger
Klaus E
KE
Andersen
Margarida
M
Gonçalo
An
A
Goossens
Jeanne D
JD
Johansen
Howard I
HI
Maibach
Thomas
T
Rustemeyer
Christophe-J
CJ
Le Coz
Ian R
IR
White
D000485:Allergens / Q000008:administration & dosage* / Q000009:adverse effects; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D010328:Patch Tests / Q000379:methods*; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects; D013844:Thiazoles / Q000008:administration & dosage* / Q000009:adverse effects
D000485:Allergens; D011310:Preservatives, Pharmaceutical; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C037057:Kathon 886; C011421:5-chloro-2-methyl-4-isothiazolin-3-one
European baseline series; MCI/MI; adverse reactions; allergic contact dermatitis; contact allergy; delayed hypersensitivity; dose/cm2 skin area; micropipette; patch test sensitization