Shingles (also known as herpes zoster) is a painful rash caused by the chickenpox virus (varicella zoster virus). If you have suffered from chickenpox before, the varicella zoster virus remains in your body and resurfaces when your immune system weakens due to aging, stress or disease. It forms a rash that appears as blisters on one side of the body. It can also affect the face and eye, causing severe pain or even blindness.

Antiviral drugs should be started within 48 hours from the onset of the rash. Usually, strong painkillers are needed, as the pain from shingles can be severe.

When the pain from shingles persists for more than 3 months after the onset of the rash, the condition is called post-herpetic neuralgia (PHN). This results from permanent damage to the nerves, leading to continuous pain, hypersensitivity and numbness in the area of the body where the rash used to be.