Skin responses to ultraviolet radiation in contact photodermatitis due to fentichlor

There are several groups of chemicals that may produce contact photodermatitis and the action spectra for photopatch tests with these chemicals have been established. Controversy exists about UVR sensitivity in patients with contact photodermatitis when tests are performed on normal appearing skin without the addition of the chemical. Four patients became "persistent light reactors" after developing contact photodermatitis from fentichlor, 3 after using a hair cream containing the chemical, the 4th after industrial exposure. Normal appearing skin on the back of the trunk was tested to narrow waveband UVR and visible light, fentichlor was not added to the skin during these tests. Abnormal reactions to UVB occurred in all 4 patients and all showed sensitivity to UVA, to 340 nm in 1, to 360 nm in 1 and to 400 nm in 2. At pH 4 fentichlor absorbed between 310 nm and 325 nm, but at pH 9.2 absorption was between 275 nm and 350 nm, there was no absorption above 350 nm. The results of tests with narrow waveband UVR show that true sensitivity to UVB does exist in the normal appearing skin of "persistent light reactors," the sensitivity is not spurious. The normal skin of these patients is also sensitive to UVA. Possible reasons for the URV sensitivity are discussed.