Hair lightening in the sun, also known as photobleaching, is a common phenomenon where hair becomes lighter in color when exposed to ultraviolet (UV) rays from the sun. This can occur over a short period of time, with just a few hours of sun exposure, and can be more pronounced in people with lighter hair or who have been in the sun for extended periods.
Hair lightening in the sun has been observed for centuries and is thought to be caused by the production of melanin, a pigment that gives hair its color. UV rays can break down the melanin pigment, resulting in lighter hair color. Hair lightening in the sun can also be affected by other factors, such as the intensity of the sunlight, the length of time hair is exposed, and individual hair characteristics.