The irritancy of metalworking fluids: a laser Doppler flowmetry study

Irritant contact dermatitis is common in metalworkers exposed to metalworking fluids (MWF). The irritancy of 3 commercially available water-based cutting fluids in maximal user's concentration and 2 neat oils was investigated in 23 healthy volunteers. Additionally, the irritancy of some groups of components of the cutting fluids was studied. After Sellotape stripping, repeated patch tests were performed over 5 days and evaluated by a visual score (VS) and by laser Doppler flowmetry (LDF). In general, the MWF caused marginal skin irritation. In a comparison of the MWF and water, the cutting fluids were ranked higher in irritancy than the neat oils, but the effect of only one cutting fluid could be distinguished from that of water. The components of the cutting fluids also caused no strong reactions. The LDF response showed that one emulsifier was more irritant than water and according to the VS, one corrosion inhibitor was the most irritant. The correlation coefficient between the VS and the LDF response was probably diminished by a strong adverse reaction to the fixing tape in many volunteers. From this experiment, it was concluded that MWF are generally only mildly irritant when used in proper concentrations. However, orthoergic contact dermatitis often develops as a result of repeated and cumulative subclinical insults, in which MWF, especially water-based, play a crucial role because exposure at work is often extensive.