Erythrulose is an aqueous solution of erythrulose, a low-molecular-weight tetrose keto-sugar. Formulators use it in self-tanning systems to generate gradual surface coloration. Non-enzymatic Maillard-type reactions drive tan formation. Free amino groups in stratum corneum proteins participate directly in these reactions. Erythrulose reacts more slowly than dihydroxyacetone (DHA). Slower reaction kinetics delay tan onset and improve color uniformity. Formulators commonly combine erythrulose with DHA. This combination moderates tanning speed and softens final tan intensity. The polyhydroxy structure contributes mild hygroscopic behavior.
