Marshmallow (Althaea officinalis) root has been used in traditional herbal medicine for centuries, primarily for its soothing, demulcent (mucilage-rich) properties that can calm mucous membranes. In the context of kidney infections (pyelonephritis), its use is based on historical practice rather than robust scientific evidence. Traditional herbalists have recommended marshmallow root for various urinary tract issues, including cystitis and irritation, because it may help soothe inflamed tissue in the urinary tract and promote urination, which, in theory, could aid in flushing out bacteria.

However, there is minimal direct scientific research supporting marshmallow root's efficacy in treating kidney infections specifically. Most available studies focus on its anti-inflammatory and mucilaginous properties in gastrointestinal or respiratory tract conditions. Some in vitro studies suggest potential antibacterial and anti-inflammatory effects, but these findings have not been directly translated into clinical evidence for kidney infections.

Overall, while marshmallow root has a long history of traditional use for urinary discomfort and may provide symptomatic relief, its use for treating kidney infections lacks strong scientific validation. Anyone with a suspected kidney infection should seek prompt medical care, as untreated infections can become serious. Marshmallow root should not be used as a substitute for antibiotics or other standard medical treatments.