Nickel chloride or nickel sulfate? Irritation from patch-test preparations as assessed by laser Doppler flowmetry.

To obtain an optimal test preparation for diagnosing nickel contact sensitivity, one can vary the nickel salt, vehicle and concentration, length of exposure, patches, and tape. Nickel chloride has been suggested as an alternative to nickel sulfate in the standard tray. However, a sensitive and noninvasive method of recording skin blood flow (laser Doppler flowmetry) showed in healthy subjects that the chloride was more irritating to the skin than the sulfate when petrolatum was used as vehicle. The naked eye could not discern this difference.