As we move into the longer and brighter days of spring and summer, we need to think about protecting our skin from the UV rays. Ultraviolet radiation exposure is the primary cause of skin cancer, wrinkles and irregular pigmentation. There is a death every hour in the U.S. due to melanoma (over 8000/yr). Of all of the skin care advice given, proper protection from the sun will make the greatest difference in one’s future appearance. All the money spent on all the cosmetic products and procedures is wasted if one does not employ good “sun sense.” Avoidance of sun exposure during the 10 am to 4 pm period and wearing sun protective hats and clothing will help. Daily use of sunscreen is also an important part of helping to protect ourselves from damaging UV rays. Anyone over six months of age should use a sunscreen daily and children under six months should not be exposed to the sun.
Much confusion surrounds Sun Protection Factor (SPF) ratings. In short, SPF is a measure of how much the product shields the sun’s shorter-wave ultraviolet B rays (known as UVB radiation). UVB is known to produce sunburn and was found to cause squamous cell cancer. The first sunscreens developed were aimed at improving UVB protection. An SPF of 15 is supposed to allow one to be protected 15 times longer from burning from the sun’s rays than unprotected. Unfortunately, this is misleading due to the fact that very few people wear the sunscreen as heavily as is tested in the laboratory. It is estimated that we are usually receiving about one third of the protection because we wear about one half as much as the sunscreen needed. An adult needs about 30 cc or 1 ounce to cover their body as the manufacturers have tested the product. The “two finger” rule indicates that one needs two finger lengths of sunscreen applied to all 11 parts of the body (each arm, each upper leg, lower leg, upper back, lower back, head/neck, etc).
The sunscreen needs to be applied 20-30 minutes prior to sun exposure and reapplied every two hours (or more often if sweating or in the water). “Water resistant” sunscreens indicate about 40 minutes of protection and “very water resistant” (water proof is no longer allowed on the label) indicate about 80 minutes of protection. The higher the SPF doesn’t always tell the entire story. An SPF 15 blocks approximately 94% of the sun’s UVB rays. SPF’s of 30 and 50 block 97% and 98% respectively. Insect repellents reduce the effectiveness of sunscreen by about one-third so if you are using an insect repellent and sunscreen together, use a higher SPF and reapply your sunscreen more frequently.
UVA rays are more penetrating than the UVB rays. They penetrate deeper into the skin’s layers and are thought to be more responsible for DNA damage and aging. The U.S. does not have a rating system for UVA protection as yet. The Japanese system of PA+ to PA++++ is a system that one will often see for UVA protection ratings on some products. One + is very poor UVA protection, while four + is high protection. UVA rays penetrate glass and do not seem to be blocked by cloud cover as much as UVB. These are the rays that we should protect against year round and are the basis for promoting the idea that sunscreen should be worn 365 days a year. Agents that block UVA rays are either chemical or physical blocking agents. Many of the chemical blocks degrade rapidly in the sun and have to be stabilized. Physical blocks such as zinc and titanium dioxides do not degrade and reflect the sun’s rays. Avobenzone and ecamsule are two examples of chemical sunscreens that block UVA rays. Avobenzone rapidly degrades in the sun and requires stabilization (Helioplex). These agents are absorbed into the skin and transform UV radiation into heat energy. The physical sunscreens reflect and refract the rays.
The Bottom Line on Sunscreens
- Sun protection needs to occur year round
- Use a sunscreen with at least an SPF 15 and one with adequate UVA coverage
- Apply at least every 2 hours and more often if sweating or in water
- Look for the Skin Cancer Foundation’s Seal of Recommendation
Dr. Jan Turkle