text: Woods lamp is useful in diagnosing conditions such as tuberous sclerosis and erythrasma (caused by Corynebacterium minutissimum, see above).  Additionally, detection of porphyria cutanea tarda can sometimes be made when urine turns pink upon illumination with Woods lamp. Woods lamps have also been used to differentiate hypopigmentation from depigmentation such as with vitiligo. A vitiligo patients skin will appear yellow-green or blue under the Wood's lamp. Its use in detecting melanoma has been reported.