English: Progression of shingles. A cluster of small bumps (1) turns into blisters (2) that resemble chickenpox lesions. The blisters fill with pus, break open (3), crust over (4), and finally disappear. This process takes four to five weeks. A painful condition called post-herpetic neuralgia can sometimes occur. This condition is thought to be caused by damage to the nerves (5), and can last from weeks to years after the rash disappears.