The appearance of a cold sore, known medically as herpes labialis, is caused by the Herpes Simplex Virus type 1 (HSV-1). This common pathogen establishes a lifelong, latent infection in the body. The question is whether the novel coronavirus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which causes COVID-19, might act as a trigger for these outbreaks. Systemic viral infections often affect the body’s immune balance in ways that can awaken dormant pathogens, highlighting how the response to one illness can influence a long-term resident virus.
Viral Illnesses and Cold Sore Reactivation
HSV-1 is a neurotropic virus that infects nerve cells, establishing a quiescent state known as latency after an initial infection. During this dormant phase, the virus retreats into the sensory nerve clusters, primarily the trigeminal ganglia, where it remains hidden from the immune system for years. The virus typically does not replicate or cause symptoms while in this latent state, but it retains the ability to reactivate.
Reactivation is often triggered by physiological stress that temporarily disrupts immune surveillance. Common triggers include:
- Excessive exposure to ultraviolet (UV) light
- Hormonal changes
- Tissue injury
- The presence of an acute systemic illness
A high fever or significant inflammation from any respiratory infection can serve as a potent signal that causes the virus to begin replicating.
When the body fights a separate infection, the immune system redirects resources, briefly lowering control over the latent virus. This temporary shift in the body’s defense mechanisms provides an opportunity for the dormant HSV-1 to travel back down the nerve axon to the skin’s surface. Once there, the virus begins the lytic cycle, resulting in the formation of the painful, fluid-filled blister characteristic of a cold sore.
Specific Evidence Linking COVID-19 and HSV-1
Clinical observations during the COVID-19 pandemic have documented numerous instances of HSV-1 reactivation occurring concurrently with or shortly after SARS-CoV-2 infection, suggesting a link. While any severe illness can trigger a cold sore, the nature of the COVID-19 infection presents unique mechanisms that may make it a strong catalyst. The intense systemic inflammation caused by the coronavirus, often described as a “cytokine storm,” creates a highly stressful environment within the body.
The resulting immune dysregulation in COVID-19 patients, especially those with severe disease, includes a reduction in T-lymphocytes. These T-cells are normally responsible for maintaining the dormancy of HSV-1 in the nerve ganglia. Their temporary depletion can weaken the immune system’s ability to keep the herpes virus suppressed, providing the window necessary for the latent virus to escape and reactivate.
Furthermore, a common treatment for severe COVID-19 involves the use of high-dose corticosteroids, such as dexamethasone, to manage the overwhelming inflammatory response. While these drugs are effective at reducing lung inflammation, they are also immunosuppressive. This immunosuppression can further predispose a patient to opportunistic co-infections or the reactivation of latent viruses.
Observational studies found higher rates of HSV-1 reactivation in critically ill COVID-19 patients compared to historical rates, with some cohorts reaching over 40%. These findings suggest that the combination of the SARS-CoV-2-induced immune response and the necessary medical treatments may create a permissive environment for the herpes virus. The association is more frequently noted in patients with severe disease, indicating that the overall severity of the COVID-19 illness correlates with the likelihood of a cold sore outbreak.
Treatment and Management During Active Infection
Managing a cold sore outbreak while simultaneously dealing with an active COVID-19 infection requires careful attention to both conditions. The primary treatment for cold sores involves the use of antiviral medications, such as acyclovir or valacyclovir. These medications work by interfering with the herpes virus’s ability to replicate and are most effective when treatment is initiated very early, ideally at the first sign of tingling.
Self-care measures manage discomfort and prevent viral spread. Applying a cold compress or taking over-the-counter pain relievers, such as ibuprofen or acetaminophen, can help reduce pain and swelling associated with the blister. It is important to avoid touching the cold sore directly, except when applying topical creams, and to wash hands immediately afterward to prevent autoinoculation or transmission to others.
Because a cold sore outbreak is occurring during a systemic illness like COVID-19, consulting a healthcare provider is highly recommended. The provider can determine if an oral antiviral prescription is necessary, particularly if the outbreak is severe, extensive, or if the patient has other underlying health concerns. The symptoms of cold sores and COVID-19 can occasionally overlap or complicate treatment, making professional guidance important.