Dermatological applications of EPR : skin-deep or in-depth?

The skin is often referred to as the biggest uniform human body organ, and also as the "brain outside", exposed not only, like the lung epithelium, to the atmospheric air but to other constituents of the open environment including changeable temperature and solar irradiation. The importance of what happens in the skin is therefore not to be overestimated for general condition of the whole organism. Techniques of electron paramagnetic resonance (EPR; called also electron spin resonance, ESR) spectroscopy and imaging belong to the important experimental and diagnostic approaches in dermatology, but the size and shape of skin often make technical problems. The present chapter will cover the basic and clinical applications of EPR to study the skin (including skin tumors) and hair. As the numerous available review papers usually describe the specificity of the EPR-related methods for dermatologists, we decided to cover also some basic aspects of dermatology, to make the chapter more useful also to the specialists in EPR theory and instrumentation. A particular emphasis will be put on the most recent discoveries and innovations, to show that the apparently purely dermatological aspects of such investigations reveal also deeper, systemic implications.