This is a common and often painful skin condition which affects people of all ages. It is caused by a virus that infects the nerve leading to a segment of your skin. The virus that causes the condition is the same one that causes chicken pox in children. If you have this condition, it means that at some time in the past you had chicken pox and the immunity that your body built up to prevent being re-infected with chicken pox, on re-exposure, has been almost completely lost. At some time in the period before your shingles broke out, you were again exposed to chicken pox, and since your body still had some protection left, instead of your whole skin and body getting a chicken pox infection you were able to confine it to the area of few skin nerves.

The infection causes the nerve to swell with pain in the skin or the area supplied by the nerve. Many areas of the skin can be affected by the infection. The most common areas are the trunk, segments of the face and neck, and along the arm or leg. All of these will follow a pattern along the course of a nerve spreading first from the area of the skin closest to the midline of the back near the spinal cord and then spreading around on only one side of the body toward the middle of the front of your body. On arms and legs it begins closest to the torso and spreads outward in the direction of the hand or foot.