Female 35. 1.5x2.5" red rash spinal area above tailbone. mild pain, light blistering. would suspect shingles if it was in any other location. thoughts?

Viral: This is possible herpes simplex, and you would benefit from an examination and some antiviral medication. In the meantime apply tepid compresses and cleanse gently with a mild soap and water.

Blisters: If the eruption is only on one side of the spine, shingles is a definite possibility. If the eruptions are on both sides or in the middle other herpes infection is possibility. Since these are all treatable, I recommend that you be examined by your physician or dermatologist for diagnosis and treatment.