Even when you are not particularly aware of sun exposure, UV rays penetrate your skin, and your skin stores a memory of this faint exposure.
This type of harmful, cumulative UV damage surfaces as signs of aging, such as wrinkles and dark spots. Sun damage can also pose health risks in the from of a weakened immune system and skin cancer.
UV rays are invisible to the naked eye. Even on rainy days when the sun is not visible, UV rays still penetrate through the clouds. Moreover, UV rays are not only found in direct sunlight, but also in all reflected light.
An effective way to protect your skin from UV rays in all directions is to block these rays at the surface of the skin by applying sunscreen in an appropriate manner.