Sun Damage and Sunscreens

Although sunlight is essential for human life, daily exposure to the sun over a lifetime is a major cause of skin damage, including wrinkling and skin cancer. The process is characterized by clinical, histological and biochemical changes that differ from changes in chronologically aged skin. While chronologically aging skin changes “gracefully”, photo damaged skin will age much faster and “ungracefully” displaying tough, leathery, dry, rough skin, among a few of the visible signs. Many of the skin changes attributed to aging are, in fact, signs of sun-induced skin damage. Sunscreens work by scattering, absorbing or reflecting UV rays. Sun blocks are opaque substances, zinc oxide and titanium dioxide, work on top of the surface to deflect UV rays away from the skin. Chemical Sunscreens work by changing UV rays into heat, and release heat from the skin. Sunlight exposes people to two kinds of UV light: UVA and UVB. Virtually all sunscreens provide some level of protection against UVA and UVB rays.
The solar spectrum is divided into the following key regions:
Visible Light (400-760nm)

• Insignificant role in photo damage

UVA (320-400nm – long wave)

• 1,000x weaker than UVB, but 100x greater in quantity

UVB (290-320nm – short wave)

• The most potent to reach the earth’s surface
• Thought to cause a majority of photo damage

UVC (270-290nm)

• Absorbed in the earth’s atmosphere

When sun shines on skin, the epidermis absorbs the short UVB rays. These generate free radicals that can destroy and mutate cells and cause the potential for skin cancer. The long UVA rays go deep into the dermis, and even through clothing and windows. These rays go deeper than UVB rays eventually destroying collagen and elastin.

• Repeated overexposure leads to photodamage:
  • Fine lines, wrinkles
  • Age spots, freckles
  • Scaly red patches - actinic keratosis, (pre-cancer)
  • Tough, leathery, dry, rough skin
  • Skin cancer: basal cell, squamous cell, melanoma
  • Eye damage - cataracts
  • Weakened immune system

Research shows that free radicals are involved in cutaneous sun damage. They are indiscriminate, destroying and/or mutating anything in their way, including collagen, elastin. Vitamin C and E are effective antioxidants when applied topically and inhibit UVB damage to the skin. Study further shows that vitamin C augments the UVB protection provided by vitamin E and a UVB sunscreen. Vitamin C, however, is more effective than E in protecting against UVA-mediated damage, protecting the cellular DNA. Applying a Vitamin C (L-Ascorbic Acid) serum prior to applying a sunscreen will provide added protection and enhance the performance of the sunscreen.
SPF sunscreen numbers only indicate the amount of time one can stay in the sun without burning. The application of an SPF 15 sunscreen should provide protection about 15 times longer than no sunscreen at all. SPF protection does not increase proportionally with SPF number. SPF 30, for example, absorbs 97% of sun burning rays, while an SPF of 15 indicates 93% absorption. SPF numbers lower than 15 probably won't offer enough protection, while those higher than 30 may not offer any additional benefits.