Alkanolamineborates are extensively used in coolants as corrosion inhibitors. In this paper, 3 machinists with contact allergy to alkanolamineborates are reported. To avoid false-positive test reactions due to the alkalinity of the alkanolamineborates, they should be tested when dissolved in an acidic buffer. When various alkanolamineborates were tested in dilution series in the 3 patients, 2 types of reactivity patterns emerged, indicating the existence of at least 2 separate sensitizers in alkanolamineborates. The raw materials, ethanolamines and boric acid, did not yield any positive patch test reactions. Thin-layer chromatography investigations demonstrated that each alkanolamineborate consists of many substances, which differed in part between different alkanolamineborates. The present study shows that it is not possible to use 1 particular alkanolamineborate for tracing contact allergy to alkanolamineborates in general.