Shingles, also known as herpes zoster, is a viral infection that causes a painful rash. This condition arises from the reactivation of the varicella-zoster virus (VZV), which is the same virus responsible for chickenpox. After an initial chickenpox infection, VZV remains in the body, lying dormant for years or even decades. When certain conditions trigger its reawakening, the virus travels along nerve pathways to the skin, resulting in a shingles flare-up.
The Dormant Varicella-Zoster Virus
Following a chickenpox infection, the varicella-zoster virus does not exit the body; instead, it settles into a latent state within specific nerve cells. These cells are typically sensory nerve ganglia, located near the spinal cord and brain. The virus can remain inactive in these nerve tissues for decades without causing any symptoms. Scientists have discovered that during this dormant phase, a particular RNA transcript within the VZV remains active, playing a role in maintaining the virus’s latency and preventing its replication. The presence of this dormant virus is a prerequisite for shingles to develop. If an individual has never had chickenpox or the chickenpox vaccine, they cannot develop shingles directly, but they can contract chickenpox if exposed to someone with active shingles. The virus’s ability to “hide” within the nervous system means that while the immune system largely keeps it in check, it is always poised for potential reactivation under favorable conditions.
Immune System Compromise
A person’s immune system plays a significant role in keeping the dormant varicella-zoster virus in check. When immune defenses weaken, the virus can reactivate and cause a shingles flare-up. Several factors can lead to a compromised immune system, increasing susceptibility to shingles.
The immune system naturally weakens with age, making older adults more prone to shingles. About half of all shingles cases occur in individuals aged 60 or older, and the risk significantly increases after age 50.
Certain medical conditions also suppress the immune system, raising the risk of shingles. These include diseases like HIV/AIDS, various cancers (such as leukemia and lymphoma), and autoimmune diseases like lupus and rheumatoid arthritis.
Immunosuppressive medications are another significant factor in shingles reactivation. Drugs like corticosteroids (e.g., prednisone), chemotherapy agents, and anti-rejection medications used after organ transplants can lower the body’s resistance to infections. Specific medications used for autoimmune conditions, such as some non-biologic disease-modifying antirheumatic drugs (DMARDs) and TNF inhibitors, also increase shingles risk by affecting T-cell-mediated immunity. Additionally, severe illness or major surgery can temporarily weaken the immune system, potentially contributing to a shingles flare-up.
Lifestyle and Environmental Stressors
Beyond medical conditions, various lifestyle and environmental factors can also contribute to shingles flare-ups, often by impacting the immune system’s effectiveness. Chronic or severe emotional and psychological stress can negatively affect immune function, making viral reactivation more likely. Stress hormones, such as cortisol, can suppress the immune system, thereby reducing its ability to keep the varicella-zoster virus dormant. While some studies show conflicting results, many indicate a link between high levels of perceived psychological stress and an increased risk of shingles.
Physical stress and trauma can also trigger shingles, sometimes localized to the injured area. Physical injury, surgery, or even intense physical exertion may stimulate the nerve where the virus is dormant, leading to a flare-up.
Inadequate sleep and chronic fatigue can compromise the immune system, diminishing its capacity to control the latent virus. The pain and discomfort associated with shingles can further interfere with sleep, creating a cycle that exacerbates fatigue. Maintaining sufficient rest is therefore important for overall immune health.
Poor nutrition can also contribute to a weakened immune response. Deficiencies in specific micronutrients, such as vitamins A, D, B12, C, E, and zinc, are linked to impaired immune function necessary for suppressing VZV reactivation. While generally a less direct cause than other factors, a diet lacking essential nutrients can hinder the body’s ability to maintain a robust defense against the dormant virus.