Most Helpful Girl
Hypochlorous acid can oxidise and degenerate melosomes in hair and skin. Melosomes are organelles that can contain melanin (which is responsible for pigment). Thus chlorinated pools can assist you in fading your hair color but by degenerating the melosomes they can also increase UV sensitivity. Of course there are quite a few hair products that provide UV protection to compensate for any loss of natural protection. So whilst chlorinated pools are not natural, swimming occasionally may assist in both lightening your skin and hair color. But if you intend on spending great lengths of time in the sun, use UV protective products for your hair and skin.
Additionally, the friction of the water also has some effect on lightening hair color, but that is primarily due to cuticle damage.