Blacky Purple blister type size, red mark around, itches like mad.

Dear Ask The Doctor: I spotted it on Monday i dont know how long it's been there, i'm not really sure what it is. It's on my back, it's blacky purple, and has a red circle around it, it really really itches, and hasnt got any better, i'm not sure what it is? I'm just checking to be sure.

Dear Lucy: It is difficult to say what may be the cause of the your skin lesion. In my opinion, your spots could be due to a fungal infection known as tinea versicolor. Treatment involves anti-fungal medications like clotrimazole, ketoconazole. I hope this helps, take care.