From the Guidelines
There is no established evidence that L-citrulline supplementation triggers or exacerbates cold sores (herpes simplex labialis). L-citrulline is an amino acid that primarily functions as a precursor to L-arginine in the body, which then contributes to nitric oxide production. While some studies have suggested that high levels of arginine might theoretically benefit the herpes virus replication, there is insufficient clinical evidence showing that L-citrulline supplementation directly worsens or triggers herpes outbreaks. The concern stems from the fact that the herpes virus may utilize arginine for replication, but the body's conversion of citrulline to arginine occurs naturally regardless of supplementation.
If you have recurrent cold sores and are concerned, you might consider monitoring your outbreaks after starting L-citrulline to see if there's any correlation. Typical L-citrulline supplements range from 3-6 grams daily, and if you notice increased frequency of cold sores after starting supplementation, you might consider discontinuing use and consulting with a healthcare provider. For those with frequent herpes outbreaks, maintaining antiviral medication like acyclovir, valacyclovir, or famciclovir as prescribed by your doctor remains the most effective prevention strategy.
Key points to consider:
- L-citrulline's role in the body is as a precursor to L-arginine, which is involved in nitric oxide production.
- Theoretical concerns about L-citrulline and herpes virus replication are based on arginine's potential role in the virus's life cycle.
- There is no direct clinical evidence linking L-citrulline supplementation to an increased risk of cold sores.
- Monitoring for any changes in cold sore frequency after starting L-citrulline supplementation is a prudent approach.
- Antiviral medications remain the cornerstone of prevention and treatment for frequent herpes outbreaks 1.
From the Research
L-Citrulline and Cold Sores
- There is no direct evidence to suggest that L-citrulline supplementation triggers or exacerbates cold sores (herpes simplex labialis) 2, 3, 4, 5.
- The available studies focus on the effects of L-citrulline on blood pressure, exercise-induced muscle damage, and intestinal inflammation, but do not investigate its relationship with cold sores.
- However, a study on the treatment of recurrent herpes simplex labialis suggests that topical creams containing antiviral agents and corticosteroids can be effective in reducing the frequency and severity of cold sore outbreaks 6.
- It is essential to note that the current evidence does not support a direct link between L-citrulline supplementation and the development or exacerbation of cold sores.
- Further research would be necessary to determine if L-citrulline has any effect on herpes simplex labialis, but currently, there is no evidence to suggest that it causes or worsens cold sores 2, 3, 4, 5.