Rash started big on one thigh. no itching, but some tenderness for a few hours - no pain now & rash decreased, but have developed blister like bumps?

Shingles: Shingles is a skin rash caused by a nerve and skin inflammation from the same virus that previously caused chickenpox. This virus is called the varicella zoster virus (VZV) and belongs to the herpes family of viruses. Treatment is with oral prescription valtrex (valacyclovir).

In the absence of: A trauma, like a burn, it's unusual to have a painless rash that doesn't itch that turns into blisters. Herpes hurts, that's ur main blister causer but u would know. It may be fungal. Try some lotrimin (clotrimazole) with Hydrocortisone daily for a few weeks and go get seen if worsens or u get sick.