Sunlight energizes and provides vitamin D, but it can also deliver damaging ultraviolet (UV) radiation. UV rays are absorbed into the skin, potentially causing wrinkles and skin cancer. Sunscreens and sunblocks effectively protect the skin against these damaging rays. Knowing the differences between sunscreens and sunblocks can help you choose the most appropriate product.
Sunscreens contain chemicals that absorb UV radiation and reduce the amount that reaches the skin, according to the American Melanoma Foundation (AMF). Sunblocks physically prevent UV radiation from reaching the skin. Sunscreens tend to be transparent and are invisible when applied, whereas sunblocks are thicker, remain visible when applied and are more difficult to wash off than sunscreens.
Sun protection products should protect against both UVA and UVB radiation. Go Sun Smart describes UVA as affecting the outermost skin layers, causing aging and wrinkles. UVB radiation damages deeper skin layers, potentially causing skin cancer. The amount of protection offered by sunscreens is measured in sun protection factor (SPF) units. The SPF level of a particular product indicates how long a person can remain in the sun without becoming burned, according to Lifespan. For example, if you use a product with an SPF of 20, you may stay in the sun 20 times longer than if you did not use any sunscreen. The higher the SPF level, the greater the protection from UV radiation. Sunblocks provide more protection against UV radiation than sunscreens, but sunblocks are not measured with SPF units, states the AMF. Sunblocks protect the skin from both UVA and UVB rays. Sunscreens protect against UVB, but not all offer protection against UVA radiation.
Sunblocks contain metallic ingredients, such as titanium dioxide, zinc oxide or iron oxide, that physically block the sun, according to Lifespan. Sunscreens may contain a variety of ingredients, but the Lifespan recommends looking for products that contain octinoxate, oxybenzone, octisalate, benzophenone or methyl anthranilate in the active ingredients.
Effective protection from UV rays depends on proper use of sunscreens and sunblocks. For maximum protection, sunscreens must be applied 30 minutes before going out in the sun to allow the skin to absorb the protective chemicals, according to Go Sun Smart. Sunscreen must be reapplied after swimming or sweating, even if the product is waterproof. Sunblock is effective as soon as it is applied and, because it remains on the skin surface, it can be applied immediately before sun exposure.
AMF recommends using sunscreens with an SPF of at least 15--higher for people with light skin. People who are especially sensitive to the sun should use sunblocks. Cream or lotions provide an amount of protection, but oils have much lower SPF levels--usually two or less--and provide inadequate UV protection. Use sun protection all year long, whether the weather is sunny or cloudy.