The science
The active mechanism of this wash is alpha-hydroxy acid exfoliation. Glycolic acid, the smallest AHA, loosens the ionic bonds between corneocytes at the base of the stratum corneum, accelerating desquamation; in leave-on products at 5 to 10 percent it has controlled evidence for improving roughness, keratosis pilaris and superficial hyperpigmentation, and in rinse-off formats the effect is attenuated by short contact time but still measurable with regular use, particularly for the follicular keratin plugs of keratosis pilaris. The declared 5 percent here is partly neutralised by sodium hydroxide, which raises the pH toward a tolerable range and reduces free acid; the brand does not state the pH, and the balance between efficacy and tolerance in an AHA wash depends on it. Glycolic acid increases ultraviolet sensitivity in the days after use, an effect documented for leave-on products and plausibly present, if smaller, for rinse-off use, which supports the advice to protect treated skin with sunscreen.
The surfactant system is designed to offset the acid's irritation potential. Cocamidopropyl betaine and cocamidopropyl hydroxysultaine are amphoteric surfactants that reduce the irritation of anionics in blends; sodium cocoyl isethionate and sodium methyl cocoyl taurate are mild anionics with low lipid-extraction scores; coco-glucoside is a mild non-ionic. Together they lather well at a pH compatible with an AHA and strip less than sulfate systems, and glycerin at ninth adds modest humectancy. Niacinamide at fourteenth contributes barrier support during the wash; its pigment effects require leave-on exposure at 2 to 5 percent and are not expected here.
The remaining ingredients have no plausible pigment activity in a rinse-off. Alpha-arbutin, kojic acid, azelaic acid and glutathione, present at trace levels late in the list, are tyrosinase inhibitors or antioxidants whose clinical evidence comes from leave-on use at working concentrations over weeks; a thirty-second contact time precludes any effect. Saccharomyces/Xylinum/black tea ferment (kombucha) has laboratory data on antioxidant and smoothing activity with no rinse-off relevance. Tolerance considerations are the acid itself on compromised, shaved or atopic skin; Citrus reticulata (tangerine) peel oil at thirteenth with limonene declared, a sensitiser whose oxidation products are frequent patch-test positives; cocamidopropyl betaine, a recognised contact allergen; and kojic acid as an occasional sensitiser. The formula is oil-free and free of comedogenic lipids. Urban Skin Rx publishes no product-specific testing.