- Sunscreens can be either physical and chemical. Physical sunscreens provide broad-spectrum protection by reflecting both UV rays. In years past, physical sunscreens were opaque (image the white-nosed lifeguard), but with improved manufacturing techniques many formulations are now available that are more transparent.
- Of all the physical sunscreens tested by the United States Food and Drug Administration (FDA), zinc oxide offers the highest protection against UV radiation exposure. Titanium dioxide filters UVA and UVB, but zinc oxide has a much wider coverage.
- Chemical sunscreens go on as an invisible cream or lotion. They act as filters that absorb and reflect UVA or UVB radiation. The FDA reports that chemical sunscreens can cause allergic reactions, including acne, itching, stinging, rashes and dryness.
- SPF rating only covers UVB protection. The current sun protection factor (SPF) rating system, established by the FDA decades ago, doesn't include UVA because its damage to the deeper layers of the skin has only recently been discovered.
- Sunscreen labels often advertise "full spectrum" or "broad spectrum" properties, meaning that they block both UVA and UVB rays. However, a 2004 Procter & Gamble study that looked at 188 United States sunscreens found that only 56 percent offered significant UVA protection, though 82 percent claimed to do so.
- UVA rays penetrate deep into the dermis, or lower layer of skin, where they can break down collagen and other proteins that keep the skin plump and firm. "That deeper penetration and deeper damage is what we think is really associated with premature aging in the skin," said Dr. Clay J. Cockerell, president of the American Academy of Dermatology.
- The UVA rays can also damage cells and DNA in the dermis, decrease the skin's immunity and generate harmful free radicals. Though the exact mechanisms remain unclear, doctors assume these actions explain why UVA exposure is also associated with skin cancer.
- UVA caused far more changes to the dermis than UVB. UVA rays also result in a marked thickening of the stratum corneum, which is similar to what one sees in photodamaged skin.
- Researchers have found that simple sunscreens provided very little protection from the stratum corneum thickening and some of the other dermal changes caused by UVA rays.
- To be well protected, your clients need a high SPF and a high UVA protecting factor at the same time. "I take care of some very well-educated people," says Stanford University dermatologist Dr. Katie Rodan. " But beyond the SPF number, they don't know anything about sunscreen or what UVA light does. It's like 'in SPF I trust,' but that's so misleading when you consider the whole picture."
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