The body’s defense to the harmful ultraviolet rays from the sun is a pigment called melanin. This wonderful molecule absorbs over 99.9% of UV light’s energy. After UV exposure our body produces more melanin, which causes our skin colour to darken (tan).
Freckles are concentrated clusters of melanin, and are very good at absorbing UV light. Here is a video that highlights the effectiveness of melanin, glasses, and – most impressively – sunscreen at absorbing UV light.