Uric acid contains non-soluble salt crystals, which present the biggest challenge to removing urine from surfaces and fabrics. The first two components can be washed away with ordinary cleaning and commercially-available urine odor products, but the uric acid crystals are extremely insoluble and remain tightly bonded to the surface. After initial cleaning and drying with ordinary products, it may appear that the problem is solved. However, any type of moisture will reactivate those remaining crystals and the smell returns, as strong as ever. There are a number of urine odor products available to the retail customer. Most are composed of surfactants (detergents) and a masking agent. A few also employ enzymes and some use alcohol as a solvent. Still others are chemicals, whose molecules encapsulate, or coat, the urine molecules "seal in" the odor. The shortcomings of these approaches are that the odor is usually addressed only temporarily, and the stain most times not at all. None appear to have success with old, dried urine deposits. In the case of pets, the problem is compounded because of their territory-marking behavior and their very acute sense of smell. Even when the urine odor has been rendered imperceptible to humans, animals detect it and are compelled to re-apply their own scent! So once an animal has "gone" in one spot, they frequently return to it again and again, no matter what we do. But now... there is Urine Off® The enzymes in UO are specifically developed to work in combination with our specially adapted microorganisms (bacteria) that actually "eat" the uric acid crystals, in addition to removing the other components of urine. Effectively removing these crystals is what distinguishes Urine Off® from the rest of the products we've tested. With the source of the odor AND the stain removed, the problem is solved. Urine Off® has a pleasant citrus fragrance and even that disappears when the product dries.