Contact allergies to the preservatives formaldehyde and methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) have been reported to appear together at a statistically significant level. Recently, revisions concerning the patch test preparations of MCI/MI, MI and formaldehyde have been recommended for the European baseline series.To investigate (i) the number of concomitant contact allergies to the preservatives, (ii) the number of concomitant contact allergies to the preservatives and the fragrance mixes (FM I and FM II) and (iii) gender differences.Patients tested with the Swedish baseline series during the period 2012-2014 at the Department of Occupational and Environmental Dermatology in Malmö, Sweden were investigated.2165 patients were patch tested with the baseline series (34% males and 66% females). Contact allergies to formaldehyde and MCI/MI and/or MI were significantly associated (p < 0.001). The associations between contact allergy to MCI/MI and/or MI and FM I and/or FM II, and between formaldehyde and FM I and/or FM II as well as, were statistically significant (p < 0.001).Contact allergies to formaldehyde and MCI/MI and/or MI are significantly associated, as well as contact allergies to these preservatives and fragrance allergy. Males and females do not differ significantly concerning contact allergy to fragrances.