Horseradish has been cultivated since antiquity, with some evidence suggesting use in ancient Egypt, and clear documentation in ancient Greek medicine, where it was recommended for a variety of ailments. It became deeply embedded in Central and Eastern European medicine and cuisine, and its pungent, sinus-clearing qualities made it a natural fit for traditional respiratory remedies long before the chemistry behind that sensation (compounds called isothiocyanates) was understood.
The plant is closely related to wasabi, and the fiery, sinus-clearing "hit" from both plants comes from the same class of chemical compounds. Horseradish's traditional use for colds, sinus congestion, and urinary complaints has persisted particularly strongly in German herbal medicine, where it remains an officially recognized supportive treatment today — a rare case of a folk remedy retaining formal medical recognition in a modern regulatory system.
Horseradish's evidence is a case where the ingredient itself is rarely tested alone, which meaningfully limits what can be said about it specifically. Most of the available clinical evidence studies horseradish combined with nasturtium in a specific German herbal product. A large cohort study of over 1,600 patients found this combination performed comparably to standard antibiotic treatment for acute sinusitis and bronchitis symptoms, though the study design (a cohort study, not a randomized trial) is a lower tier of evidence than an RCT, and results for urinary tract infections were less favorable than antibiotics.
Laboratory studies do show horseradish's isothiocyanate compounds have measurable antimicrobial activity against a range of bacteria and fungi in vitro, providing a plausible mechanism. However, as one academic review bluntly put it, a search of the medical literature "failed to find any clinical trials on horseradish alone" — meaning the specific contribution of horseradish, separate from its typical herbal partner, remains genuinely unclear. This combination of promising mechanism, real combination-product data, but no isolated ingredient trials is why "Limited" is the accurate rating.
Fresh root grated and used as a pungent condiment, or prepared as a tincture; traditionally eaten raw for its strongest effect, since heat destroys much of its active compound.