Shingles is caused by the activation of the varicella-zoster virus that lurks in the ganglia of the body. Herpes zoster is a viral infection of the skin that occurs in most people when they are first infected with the varicella-zoster virus in the form of chickenpox or an occult infection. Thereafter, the virus can lurk in the posterior root ganglia of the spinal cord or the sensory ganglia of the cranial nerves. When the body’s immune system is low, this part of the latent virus may be activated, and the re-activated virus will be transferred along the sensory neurons to the corresponding parts of the skin, damaging the nerves, and causing lesions such as the blisters of herpes zoster, which is accompanied by painful symptoms. The presence of shingles requires prompt medical attention and early treatment.