Differences between sunblock and sunscreen

Aug 7 2007

Many people don't realize there's a difference between sunblock and sunscreen. True to its name, sunblock reflects the sun's rays, thereby blocking them from reaching your skin.

Sunscreen absorbs rather than reflects ultraviolet (UV) radiation, explains a new edition of Skin Care and Repair , a Harvard Medical School report.

Sunblocks, such as zinc oxide and titanium dioxide, are highly effective in protecting against both UVA and UVB rays, the types of UV radiation that cause sunburn and skin cancer. Sunblocks often appear white on the skin. Sunscreens tend to be less visible on the skin. They usually contain benzophenones, which protect against UVA, and cinnamates and salicylates, which protect against UVB. You'll see these ingredients listed as oxybenzone, octyl salicylate, or octyl methoxycinnamate, to name a few. A major drawback of these sunscreen ingredients is that they often break down after several hours of exposure to sunlight, which means you need to reapply them.

But two new sunscreens—Anthelios SX and Helioplex—provide longer-lasting protection against UVA and UVB rays. Research shows that Anthelios SX, which was approved by the FDA in 2006, retains 80% of its UVA protection and 90% of its UVB protection five hours after application.

The American Academy of Dermatology recommends using sunscreen with an SPF rating of at least 15. People with fair skin or at high risk for skin cancer may want to go higher. The higher a sunscreen's SPF rating, the longer it protects against sun exposure. Products labeled “broad spectrum” often contain several different sun protection ingredients in order to cover a broad range of UV radiation.

Skin Care and Repair is a 44-page report edited by Kenneth A. Arndt, M.D., clinical professor of dermatology at Harvard Medical School and director of SkinCare Physicians. This report also discusses:
• Common skin conditions
• Skin's aging process
• Skin protection
• What lotions can really do
• Skin rejuvenating procedures

Skin Care and Repair is available for $16 from Harvard Health Publications, the publishing division of Harvard Medical School. Order it online at www.health.harvard.edu/SCR or by calling 1-877–649–9457 (toll free).