The science
A cleanser's science is its surfactant system and its pH, and this one gets both right. Cocamidopropyl betaine is an amphoteric surfactant that carries both charges at skin pH and binds keratin far less than sulfates; sodium lauroyl sarcosinate is an N-acyl amino acid anionic with a bulky head group and low critical micelle concentration, which limits free monomers available to penetrate the stratum corneum. Blended, the two form mixed micelles that lower irritation below either alone while producing a dense foam, and a formulation held near skin's own pH avoids the alkaline swelling and lipid extraction that make true soaps, including the brand's bar, drying. Polyquaternium-10, a cationic cellulose polymer, deposits a thin conditioning film on rinsing. This is the chemistry behind the comfortable, non-tight feel the brand advertises, and it is well established. The documented exception is betaine's sensitisation record, attributed mainly to manufacturing impurities, which is why it appears on standard patch-test series.
The brightening actives are a different matter, because their evidence is leave-on evidence. Niacinamide reduces the transfer of melanosomes from melanocytes to keratinocytes and has controlled-trial support at 2 to 5 percent in serums and moisturisers applied daily for weeks; at a declared 4 percent here it is dosed to that standard but exposed for a minute and rinsed, so only a small fraction of the effect can be expected. Azelaic acid inhibits tyrosinase and is an established prescription treatment for hyperpigmentation and acne at 15 to 20 percent applied twice daily; its concentration here is undisclosed and its position seventh on the list is consistent with a low level. Alpha-arbutin releases hydroquinone slowly to inhibit tyrosinase in leave-on use at 1 to 2 percent; kojic acid chelates the copper in tyrosinase and works at 1 to 4 percent over months, and it is an antioxidant-stabilised, sensitising molecule rather than the exfoliant the brand's copy names it. Glutathione, phytic acid, the black tea ferment and licorice glabridin round out a roster of tyrosinase-pathway ingredients none of which has been shown to alter pigment from a rinse-off. Star anise oil supplies anethole for scent. Urban Skin Rx publishes no testing of the cleanser, and the reasonable expectation is a mild, well-formulated wash whose even-tone contribution is limited to not adding irritation.