In this work, we report the demonstration of the capability of electrochemical sensors to provide measurements directly on the sweat of volunteers to successfully discriminate heavy smokers by light ones. Since its importance as pharmaceutical treatment-agent for nicotine replacement therapy for purposes of tobacco cessation, and since that is the key compound for the development of reduced-risk cigarettes by tobacco industry, nicotine is one of those markers that are of interest for monitoring in human sweat. Especially in therapies for purposes of smoking cessation, easy methods for an easy measure of nicotine on the patients is highly required for a fine adjustment of the nicotine dosage as release, e.g., by through therapeutic patches. Therefore, we have checked the use of a simple, inexpensive and very sensitive electrochemical sensor for quantification of nicotine in smokers' sweat. Proposed sensor is capable for fast, label-free and pretreatment-free detection of nicotine in human sweat as collected directly from the skin of heavy and light smokers. Our finding demonstrates as we can detect nicotine from human skin with sweat-collecting patches thanks to its lower detection limit (0.59 mu M) as compared to the physiological limit of nicotine in human blood (12.33 mu M), while keeping under control the selectivity with respect various interfering compounds find in sweat too.