Sambucus nigra (elderberry) has a long history of traditional use for treating colds and flu-like symptoms, especially in European herbal medicine. In recent years, this traditional use has been partially supported by scientific studies. Elderberry extracts, particularly standardized syrups, have been investigated in several randomized, placebo-controlled clinical trials. Some of these studies indicate that elderberry supplementation may reduce the duration and severity of cold symptoms in adults, likely due to its content of flavonoids and anthocyanins, which may have antiviral and immunomodulatory effects.

For example, a 2016 meta-analysis (Tiralongo et al., 2016) and a 2019 systematic review (Hawkins et al., 2019) concluded that elderberry supplementation appears to substantially reduce upper respiratory symptoms. However, the number of high-quality studies is limited, and most trials have small sample sizes and short durations. The mechanism of action is not fully understood, but laboratory research shows that elderberry extracts can inhibit replication of common cold viruses in vitro and may boost cytokine production.

Overall, while elderberry's use for colds is rooted in tradition, there is moderate scientific evidence from human studies supporting its benefit in reducing cold symptom duration and severity. However, more rigorous, large-scale studies are needed to confirm efficacy and safety.