Non-invasive measurement of the vascular dynamics of dermographism--comparative study in atopic and non-atopic subjects.

There is no dissent about the vascular origin of dermographism (D); however, the microcirculatory events underlying this phenomenon are not yet elucidated sufficiently. In particular, the vascular mechanisms producing the white D pattern in atopics are a matter of divergent hypotheses. In order to quantify the D phenomenon reproducibly, we constructed an easily usable device called "Dermographometer" which enables us to apply constant stretching pressure to the skin. We were able to investigate several parameters of microvascular cutaneous reaction to defined skin stretching pressure by laser-Doppler-microfluxmetry and infrared-thermography. These measurements were performed on 23 patients with atopic eczema (AE) and 21 healthy controls under standardized investigative conditions. Only patients under similar therapeutic regimens (no corticosteroids) with dry or lichenified skin inflammation (lumbar area) were included in the study. The basic values of laser-Doppler-fluxmetry (LDF) showed a significant reduction in the intensity of hyperemia in the patients from those in the normal controls; this reaction depended on the visual degree of the dermographic blanching effect (white, delayed white, indifferent, pale-red). Patients with white or indifferent D had the lowest rises in blood flux; those with delayed white or pale-red D had more elevated blood fluxes, but these were still clearly below the mean levels of normal red D. Infrared-thermography showed a significant diminution of both the rise and plateau phase of the radiating temperature in comparison to the controls. Our results support the hypothesis that white D (including different subtypes of its pallor) depends on the degree of local vasoconstriction, possibly in combination with altered blood flow in cutaneous shunt vessels.