This investigation evaluates electrodermal (ED) testing in 41 polysymptomatic allergic patients. Electrodermal testing discriminated correctly 82% of the time between house dust mite and histamine (allergens) and saline or water (nonallergens) in our first study group involving 17 patients (p = 0.007). The second study involved 24 patients and used the same double-blind methodology discriminating 96% of the time between allergic and nonallergic substances (p = 0.000002). We conclude that ED testing is a reliable method of differentiating between allergic and nonallergic substances in the context of our study.