Herb Robert (Geranium robertianum) has a long history of traditional use in European herbal medicine, including as a remedy to support the immune system and prevent colds. Folk medicine has used the plant as a general "strengthener" and to treat various infections and inflammations, with some herbalists recommending its use to prevent or ameliorate symptoms of common colds. Its traditional application is often based on anecdotal evidence and historical texts, rather than on modern scientific research.

The purported immune-supporting effects are sometimes attributed to the plant's content of tannins, flavonoids, and other phytochemicals, which are thought to have general antimicrobial or anti-inflammatory properties. However, there is a lack of robust clinical or laboratory evidence to support these claims specifically in relation to cold prevention. No well-designed human clinical trials have been published that demonstrate efficacy of Herb Robert in preventing or treating colds. As such, its use for this purpose remains rooted primarily in traditional herbal practice rather than scientific validation.

In summary, while Herb Robert is sometimes mentioned in herbal traditions as supportive for colds, there is minimal scientific evidence to justify its use for this purpose.