UVA URSI BEARBERRY Uva ursi (bearberry) Arctostaphylos can be toxic: Hydroquinone, a component of uva ursi, can cause serious liver damage. Uva Ursi acts as a mild diuretic. As a diuretic this should be used with great CAUTION as diuretics can adversely affect kidney functioning. Uva ursi should not be taken longer than 2 weeks because of the release of high levels of hydroquininone. Bears enjoy the fruit, thus the name bearberry.