You frequently hear about the importance of wearing sunblock or sunscreen before going outdoors to protect your skin from the damaging effects of the sun. You may not realize, however, that the terms "sunblock" and "sunscreen," though often used interchangeably, are not identical. According to Medical News Today, sunblock, as the name implies, reflects ultraviolet (UV) rays and blocks them from penetrating your skin. Sunscreen, on the other hand, prevents sunburn by absorbing the sun's rays.
Effects
Sunblock lotions often appear white when they are applied to the skin. They typically contain ingredients such as zinc oxide and titanium dioxide. Sunblocks offer substantial protection against both UVA and UVB rays. UVB rays are more apt to cause sunburn and skin cancer than UVA rays.
Considerations
Sunscreens are generally colorless and become invisible when applied to the skin. Sunscreens contain benzophenones, which protect against UVA rays, and cinnamates and salicylates, which guard against UVB exposure. Sunscreens must be reapplied about every two hours because their ingredients degrade and wear off.
SPF
The sun protection factor (SPF) of a sunblock or sunscreen is determined by how long it takes for sunburn to develop with its application compared with going without protection. For example, if a person who would usually become red after 10 minutes of sun exposure uses an SPF 2 sunscreen, he could remain in the sun for 20 minutes before turning red.
Skin Type
Your skin type will determine what SPF is best for you. The American Academy of Dermatology says fair skin types that are prone to burning should use an SPF of 20 to 30. Individuals with medium-colored skin who tan easily may only require an SPF of 4 to 8. Sunblock products with high SPFs will provide longer protection against the sun's harmful effects.
Benefits
When used as directed, sunblocks and sunscreens protect against sunburn. The Mayo Clinic says they may also help prevent premature wrinkling of the skin and skin cancer.
