Evidence supporting the use of: Quercetin
For the health condition: Cold Sores

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

Quercetin is a plant flavonoid found in many fruits and vegetables, and it has been investigated for various health benefits, including antiviral effects. Regarding cold sores, which are caused by herpes simplex virus (HSV), there is some limited scientific evidence suggesting that quercetin may inhibit viral replication. Several in vitro studies have demonstrated that quercetin can interfere with HSV-1 activity by inhibiting the viral DNA polymerase and possibly blocking entry or replication within host cells. For example, a study published in Antiviral Research in 1990 found that quercetin could reduce HSV-1 replication in cultured cells. More recent laboratory studies have also confirmed quercetin's inhibitory effects on HSV-1 and HSV-2, primarily in cell cultures, by disrupting the viral life cycle and reducing inflammation associated with viral infection.

However, clinical evidence in humans is lacking. There are currently no large-scale or well-controlled clinical trials demonstrating that quercetin supplementation or topical application is effective in preventing or treating cold sores in humans. The available evidence is mainly preclinical (laboratory and animal studies). Nonetheless, due to its antiviral properties observed in the lab, quercetin is sometimes included in dietary supplements marketed for immune or cold sore support. In summary, while there is a scientific rationale and some preclinical support for the use of quercetin against cold sores, strong clinical evidence is still insufficient, making the overall evidence modest (rated 2 out of 5).

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