Chlorhexidine gluconate and acetate in patch testing

Patch testing to chlorhexidine is usually performed with chlorhexidine gluconate aq. We report the results of 297 patients, almost all with leg ulcers, concomitantly tested with chlorhexidine acetate 1% aq. and chlorhexidine gluconate 1% aq. 39 patients had positive reactions to one of these compounds or to both. 36 positive reactions to the acetate were found, in contrast to 18 reactions to the gluconate. The reactions were considered relevant in 22 of 39 patients, since these patients had developed an eczema in an area where a chlorhexidine compound was used, and discontinuing the chlorhexidine compound resulted in improvement of the condition. In 10 of these 22 patients, the diagnosis would have been missed if the gluconate only had been used for testing, while the acetate failed to diagnose 2 patients. In 109 patients without leg ulcers, inconclusive patch test readings (i.e., irritant reactions or weak positive reactions) were found in 17% with chlorhexidine acetate 1% aq., compared to 5% with chlorhexidine gluconate 1% aq., indicating a high degree of irritant potential of the acetate 1% aq. We consider that some positive reactions are lost if chlorhexidine gluconate 1% aq. only is used for patch testing, but that chlorhexidine acetate 1% aq., on the other hand, is an unacceptably strong irritant. We therefore suggest that further testing with chlorhexidine acetate 1 and 0.5% aq. should be performed, in parallel with chlorhexidine gluconate 1% aq., in order to establish appropriate test concentrations. We find that up to 13% of the leg ulcer patients in this study may be sensitized to chlorhexidine, and we recommend that the indications for the drug in leg ulcer patients should be reconsidered.