Photoplethysmography as a New Tool for Dermographism Quantitive Evaluation

Dermographism urticaria, which affects up to 5% of the general population, is defined by intensive reaction to mechanic impact on skin expressed in wheals and heavily decreases the quality of patient life. The diagnosis of dermographism is based on a provocative test, which is subjective and qualitative, highly dependent on the expertise of the medical staff. At the same time, it has been well established that capillaries are the first structures to react to external stimuli. To estimate this response quantitatively, we propose analyzing changes in capillary blood flow after a test. To assess the efficacy of this approach, we performed a provocative test on both a healthy control individual and a patient with dermographism. The condition of the capillaries was evaluated using imaging photoplethysmography. Photoplethysmographic signals were acquired both before and after provocative test to compare changes in blood flow. The findings indicate that the relation of photoplethysmogram amplitudes before and after the test differs for people with and without dermographism. We believe our outcomes can be useful for developing new techniques and tools for diagnosing and quantifying dermographism.