Cranberry extract is used to prevent urinary tract infections in dogs. Cranberries contain citric, quinic, benzoic and oleic acids, vitamins C and P, carotene, saponins, amino acids, rutin, quercetin, glycoside, trace elements (iodine, iron, copper, manganese). Cranberry contains tannin, which prevents bacteria from sticking to the walls of the bladder and subsequently removes bacteria with urine. This helps prevent infections in your pet's urinary tract.