Centre of Evidence Based Dermatology

How to perform a Minimal Erythema Dose (MED) test

The HI-Light Vitiligo Trial is testing the effectiveness of home-based light therapy using hand-held units and topical steroid for the treatment of vitiligo.

Prior to commencing treatment with narrowband UVB, a Minimal Erythema Dose (MED) test is performed to identify a patient’s individual sensitivity to narrowband UVB and ensure that the patient receives a starting dose of narrowband UVB suitable for their individual skin.

In the HI-Light trial all participants will start at the same starting dose, and the MED test is mainly performed to rule out photosensitivity.

The MED test involves a small hand held machine, which exposes the skin to ten fixed incremental doses of narrowband UVB. Readings are taken 24 hours later when the effect of the narrowband UVB has reached its peak.  The MED is the lowest dose needed to produce a clearly demarcated area of redness, or erythema, on the skin.



Dr Jonathan Batchelor has developed a training resource to demonstrate how to perform an MED test.

The training resource is available to download as a PDF document or as a Powerpoint presentation:

MED testing training resource PDF format

MED testing training resource Powerpoint file


Disclaimer: This resource was developed as part of the HI-Light Vitiligo Trial, which is funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme (project number 12/24/02). The views and opinions expressed herein are those of the authors and do not necessarily reflect those of the NIHR, NHS or the Department of Health.

Centre of Evidence Based Dermatology

The University of Nottingham
Applied Health Research Building
University Park, Nottingham

telephone: +44 (0) 115 84 68631
email: cebd@nottingham.ac.uk