Shingles (Herpes Zoster)

After a person has had varicella, varicella-zoster virus remains dormant in sensory nerve ganglia. Years later, age-related immune changes or immunocompromise may allow the virus to reactivate. It travels along one sensory nerve and inflames the nerve and overlying skin, producing neuropathic pain followed by a unilateral vesicular eruption. The pattern is usually striking: burning, stabbing, tingling, or extreme sensitivity begins in a band-like area, then grouped fluid-filled vesicles appear in the same dermatome. The rash generally stays on one side and does not cross the midline. Vesicles become pustular, then crust over. Pain may be severe even when the visible rash is small because the nerve itself is inflamed. The affected ganglion determines the risk. Involvement of the ophthalmic branch of the trigeminal nerve can threaten the cornea and vision. Ear vesicles accompanied by facial weakness or hearing symptoms suggest cranial-nerve involvement and require urgent assessment. A widespread eruption is not the usual localized pattern and raises concern for disseminated disease, particularly in an immunocompromised person.