Squill (Urginea maritima), also known as sea onion, has a long history of use in traditional medicine, particularly in the Mediterranean region. However, its primary historical uses have centered around its expectorant and cardiotonic properties, with documented applications for treating heart failure, cough, and as a diuretic. The use of Squill to support or treat urinary tract infections (UTIs) is not a major theme in traditional medical literature, but it has sometimes been included in diuretic formulas with the rationale that increased urine production may help "flush out" the urinary tract. This rationale is based more on traditional beliefs about diuretics aiding urinary health rather than direct antimicrobial action or specific effects on UTI pathogens.

Scientifically, there is little to no robust evidence supporting the use of Squill for UTIs. Modern research on Squill has primarily investigated its cardiac glycosides and their effects on the heart, rather than any antibacterial or direct urinary tract benefits. No high-quality clinical trials or pharmacological studies demonstrate that Squill is effective in treating or preventing urinary tract infections. The evidence rating of 1 reflects the presence of a tenuous traditional rationale (as a general diuretic) but a lack of focused historical or scientific evidence specifically for UTIs.