A bronzer works like a colored cosmetic to provide a tan color instantly. Because the color is visible, bronzers are useful color guides to ensure even and streak-free application for a natural appearance. While immediate, the color that bronzers impart; however, is transient and washes off quite rapidly. Typical bronzers include caramel, carmine and other colorants used in cosmetic products.
A sunless tanner on the other hand takes time to develop but lasts longer. A sunless tanner contains a reactive material like dihydroxyacetone (DHA) as the tanning agent . DHA combines with amino acids and proteins found in the skin to create the color of the sunless tan. Unlike natural tans that come from melanin, the color that develops from sunless tanners only occurs in skin's outermost layer. A sunless tan typically develops in 2-4 hours and lasts several days.
Nowadays, sunless tanning products commonly contain a bronzing agent in combination with DHA. The bronzer helps ensure even application and provides instant color in the short-term, while DHA generates color that arises more slowly but lasts substantially longer.