<prompt> Which of the following is done for the quick diagnosis of Erythrasma ?BiopsyKOH examinationCulture and sensitivityWoods lamp examination  <response>: Ans isd i.e. Woods lamp examinationRef. IADVL text book of dermatology 3de p. 236.Erythrasma is caused by infection by Coryneform bacteria.Woods lamp examination is a commonly used test to diagnose Erythrasma.Lesion shows coral red fluorescence dre to coproporphyrin III production by the bacteria. 