Heather (Calluna vulgaris) has a long history of use in traditional European herbal medicine, particularly in the British Isles and Scandinavia. Traditionally, the flowering tops of heather have been used as a diuretic and for the treatment of urinary tract ailments, including bladder infections (cystitis). The basis for its use lies mainly in folklore and the writings of herbalists from the 17th to 19th centuries, who recommended heather infusions to "cleanse the kidneys and bladder" and to "soothe urinary passages."

The plant contains various bioactive compounds, such as arbutin (also found in bearberry), flavonoids, and phenolic acids, which are believed to contribute to its diuretic and antimicrobial properties. However, unlike bearberry or cranberry, there is a lack of robust scientific studies or clinical trials investigating the efficacy of heather specifically for bladder infections. Most claims regarding its antimicrobial or anti-inflammatory effects in the urinary tract are based on extrapolation from its chemical constituents rather than direct evidence.

In summary, the use of heather for bladder infections is supported primarily by traditional herbal practices, with anecdotal and historical evidence but minimal scientific validation. Its rating is low due to the absence of clinical data or modern scientific studies substantiating its effectiveness for this purpose.