Elder flower (Sambucus nigra) has a long history of traditional use in Europe for treating colds and flu-like symptoms. More recently, elderberry (the fruit of the same plant) has received considerable scientific attention, but the flowers have also been studied to a lesser extent. Elder flower is thought to promote sweating (diaphoretic effect) and has been traditionally used in teas for feverish conditions such as colds. Some in vitro studies suggest elder flower extracts possess antiviral properties, particularly against influenza viruses, due to their content of flavonoids and phenolic compounds. However, clinical trials directly evaluating elder flower (as opposed to elderberry) for cold treatment are limited and generally of low methodological quality or small sample size.

The most robust scientific evidence pertains to elderberry, not elder flower, with several studies showing modest benefits in reducing duration and severity of cold and flu symptoms. For elder flower, evidence is largely extrapolated from its traditional use and some preliminary laboratory research. As a result, the scientific evidence supporting elder flower’s use as an antiviral for colds is limited but not nonexistent, justifying a rating of 2. It is still commonly included in European herbal cold remedies, often in combination with other herbs.