What ingredient is commonly found in self-tanners that reacts with skin to create a tan?

Dihydroxyacetone (DHA) is the key ingredient commonly found in self-tanners that interacts with the skin to produce a tan. DHA is a colorless sugar that, when applied to the skin, reacts with the amino acids in the outer layer of the skin to create a brown color. This process is known as the Maillard reaction, which is similar to what happens when food is cooked and turns brown.

Unlike melanin, which is the natural pigment produced by the skin that gives it color and protection from UV rays, DHA does not occur naturally in the body. Erythrolose is another sugar that is sometimes used in combination with DHA to enhance the tanning effect, but it is less common. Bronzer, on the other hand, is typically a cosmetic product that can provide an immediate tint to the skin but does not create a lasting tan like DHA does.

Thus, DHA is the primary ingredient responsible for the formulation of self-tanning products and is recognized for its effectiveness in producing a natural-looking tan without sun exposure.