For six years ive been getting a blistery rash on finger and knee. starts out as pain and itching, then a day or so later a bubbly rash appears. it looks like tapioca pudding. it happens at random. now it just started to appear on the sole of foot?

Blisters can be caused by many skin and systemic disorders, and location may pinpoint the diagnosis. For small areas, does it follows a specific skin pattern called dermatome? It could be shingles. Grouped, painful, and one is sexually active? Herpes simplex. Hands/Feet? Eczema, friction/sucking blisters, erythema multiforme, epidermolysis bullosa simplex, fungal infection.