Modern Approaches for the Objective Assessment of Minimal Erythema Dose

Abstract

At present, the assessment of the degree of ultraviolet (UV) exposure is based on the calculation of the minimal erythema dose (MED). The concept of MED is inextricably linked to the process of acute UV skin damage, which is accompanied by damage to the structures of the epidermis and dermis, dermal vasodilation, and it manifests clinically in erythema formation. The knowing of the MED value is necessary to choose the starting dose for UV-phototherapy of various dermatoses and to evaluate individual photosensitivity.
 Meanwhile, the determination of MED in clinical practice is most often performed visually by naked eye. The traditional assessment of MED is a subjective, inaccurate, poorly reproducible and not quantifiable method. In addition, preliminary UV irradiation is necessary for the estimation of MED and waiting for the results takes 24 hours. Inaccurate determination of MED may lead to the wrong dosing of UV-exposure, which leads to various complications.
 Today, there are a number of non-invasive methods that allow making the calculation of the MED more objective and accurate. However, these techniques have a number of limitations: the difficulty in mastering the methods, the lack of standardization of the data recording process and the evaluation of results. The majority of methods are based on the assessment of the subjective parameters of UV erythema, but not its objective pathophysiological criteria. In addition, available technologies still do not allow to estimate the MED in the first hours after UV exposure (on-site) or predict MED without UV exposure.