Urea is a long-lasting humectant that is part of the skin's natural moisturizing factor (NMF), a group of substances that ensure the moisture balance of the skin. Topical use can play an important role in helping to strengthen the skin's barrier and reduce several triggers of dry skin.
Although it is also a component of urine, synthetiUrea can increase the absorption of other cosmetic ingredients such as retinoids. It can also affect the pH of water-based solutions, so it is sometimes used to help stabilize a formula's ideal pH range.
Although it is also a component of urine, synthetic versions are used in cosmetics. In amounts between 3-5%, urea has beneficial water-binding properties that are proven to moisturize and soften the skin. Amounts of 10% or more have mild to significant exfoliating properties that have been shown to reduce dry, scaly skin and help prevent water loss.
Larger concentrations (such as 40%) of urea can cause sensitivity, although such large amounts can also thoroughly exfoliate the skin and have also been shown to significantly reduce severe dryness and rough, thickened texture. Larger amounts of urea are sometimes combined with salicylic acid in products intended for spot use on calloused feet.
Note that high concentrations of urea are not the most aesthetically pleasing, as they are potentially difficult to spread and leave a particularly tacky finish, not to mention an unpleasant, ammonia-like smell. On the other hand, the smell probably won't be much of a problem if you apply to your lower extremities instead of your face or neck.
It has a long history of use in dermatology, and scientific reviews over the years have consistently shown that urea is safe and generally well tolerated as used in skin care. https://www.paulaschoice.com/ingredient-dictionary/ingredient-urea.html?q=Urea&fdid=ingredients