Shingles (herpes zoster) can only occur in people that have previously had Chickenpox. Chickenpox is never completed eradicated from the body and lies dormant. It can be reactivated at any time by a number of causes, one of which could be excessive stress. The result is normally a localised rash which could be painful or itchy. Other things that may cause shingles are being run down, old age or weakened immune systems.
Stress can cause shingles because chronic stress will affect the immune system. Normally, during a stressful event the body will change the way the immune system will work. This is done by passing adrenaline and cortisol through the bloodstream. In terms of the immune system this will increase the consistency of the blood to make it thicker or sticky. This is in case of injuries that require clotting to seal the injury. This will increase the amount of plasma in the blood. Should the body become injured it will have to fight off potential bacteria and disease. The immune system responds by producing more white blood cells which fight against foreign bodies that may harm the body.
This is fine for sudden stress but if the stress is prolonged and becomes chronic then the immune system is constantly on high alert. This will mean the blood will be thicker than normal which can have further health complications. There will be too many white blood cells in the bloodstream than is needed. An over stimulated immune system has two consequences for the body. It works too well and starts to attack parts of the body or bacteria that live in the body that work in synergy with the body to attack disease. Or, it becomes so conditioned to working at a heightened level that it does not respond to mild diseases or ailments that enter the body. This is why people that are under stress often complain about catching colds easily. This generally leads to a feeling of being run-down and tired.
In the case of shingles, it is believed that the immune system is weakened and the body is run-down. This contributes to the reactivating of the chicken pox virus, as the body cannot suppress the virus. This leads to rashes occurring on the body that can be painful or itchy. The rashes can last for days weeks or months. In some cases they can last for years. For temporary relief you can apply a soothing agent like aloe vera, for example. If the rash persists it is advisable to consult your doctor.