What determines how dark a tan will become?

The darkness of a tan is primarily determined by melanin, which is the pigment responsible for the color of the skin. When the skin is exposed to ultraviolet (UV) radiation from the sun or tanning beds, melanocytes, the cells that produce melanin, increase their activity to protect the deeper layers of the skin. This process results in the production of more melanin, leading to a darker skin tone as the pigment absorbs UV light and minimizes damage to the underlying layers of skin.

Melanin not only provides skin coloration but also plays a crucial role in UV protection, allowing the skin to tan as a natural defense mechanism against harmful UV rays. The more melanin produced, the darker the tan will appear. Other skin components like keratin, collagen, and elastin function in different capacities, such as providing structure and elasticity to the skin, but they do not directly influence the pigmentation level that results in a tan.