Sunscreen, which contains organic chemical compounds such as octyl methoxycinnamate, octyl salicylate, and ecamsule, relies on a chemical reaction to absorb UV light and convert it into heat, which is then released from the skin, London-based dermatologist Cristina Psomadakis tells Health.
On the other hand, sunblock contains mineral ingredients like titanium dioxide or zinc oxide that physically block UV rays. So the main difference in sunscreen and sunblock lies is the way they protect the skin from UV rays. Sunblock is so named because it literally blocks UV rays by forming a physical shield, while a sunscreen contains chemicals that absorb UV rays before your skin can.
Sunscreen and sunblock also have different application methods. Because sunscreen only works when it’s absorbed by the skin, it needs to be rubbed in. But you can simply slather sunblock on, since it acts as a physical barrier. You do have to apply sunblock evenly, though, since UV light can hit any exposed parts of the skin, no matter how small. Because sunblock isn’t rubbed in, it normally leaves a white cast on the skin, while sunscreen disappears completely.
Generally, sunscreens are designed to protect against UVA rays, which promote skin damage. Sunblocks, however, are formulated to stop the damage caused by UVB rays, the kind that cause a sunburn. But many sunscreens and sunblocks tick both boxes, helping to prevent wrinkles and sunburn.