SUNSCREEN

Sunscreens are topically applied products that contain UV filters and thus protect the skin from ultraviolet light. UV filters may be separated into organic (chemical) e.g. avobenzone, octinoxate and inorganic, e.g. titanium dioxide, zinc. Iron oxide provides protection against visible light.

Types of Ultraviolet Radiation

UVB (290-320 nm)

• Key mediator of sunburn.
  
• SPF is a measure of UVB protection.
• Unfortunately, according to Consumer Reports, the majority of sunscreens did not provide the SPF promised on the bottle.
• Most organic (chemical) UV filters approved by the FDA protect against UVB.

UVA (320-400 nm)

• UVA plays a role along with UVB in photo aging (e.g. wrinkles)
• Some organic filters protect against UVB and an adjacent portion of UVA (320-340 nm), e.g. oxybenzone.
• Avobenzone is the only commonly used Food and Drug Administration-approved organic filter that protects against the entire spectrum of UVA.
• Zinc oxide and titantium block UVB and UVA but zinc oxide is more effective than titanium in the long wave spectrum (340-400 nm).

Visible Light (400-700 nm)

• Visible light (VL) plays a role in pigmentary disorders, e.g. melasma, photodamage for those with skin of color, lentigos and post-inflamatory hyperpigmentation.
• Iron oxides and antioxidants are additive ingredients that expand sunscreen protection to include VL.

SPF

• SPF is a measure of how well a product protects against sunburn. It does not convey any information on protection from UVA or visible light.
• With proper application (ie, at a surface density of 2 mg/cm2), an SPF 30 sunscreen should permit the wearer to spend 30 times more time in the sun before developing the same level of redness as if they had not applied sunscreen.
• In the real world, most people apply about a third of the above 2 mg/cm2.
• A randomized study showed that sunscreens labeled SPF 30 and 50+ provided actual mean SPFs of 9 and 14, respectively, when applied at 0.5 mg/cm2, which was thought to be more reflective of real-world use.

Sunscreens may not be as good as their SPF says.

• According to Consumer Reports, the majority of sunscreens did not provide the SPF promised on the bottle. There UVB protection ratings reflect each product’s effectiveness after water immersion.
• In a well-designed study, SPF 100+ sunscreen was more protective than SPF 50+ in actual use.

Sunscreen Tips

• Pick a broad spectrum sunscreen of at least SPF 30. But the higher the better!
• Don't trust the SPF on the bottle. If you get red or pink after using and being in the sun, switch.
• Apply 15-30 minutes before going outside.
• Goop it on! Most people only apply half of what they should.
  
• Reapply every 2 hours while outdoors or sooner after swimming or sweating.
• Avoid the sprays (Breathing in sunscreen! What does that do?)
• Kids and adults can use the same sunscreen.
  
• To put on enough sunscreen all over, you need about 14 minutes!!
• Alongside sunscreen, seek shade and wear protective clothing including long-sleeved clothing, hats, and sunglasses.

Sunscreens prevent:

• Actinic keratoses
• Photo-aging
• Squamous Cell carcinoma
• Melanoma.

Babies and Children

Sunscreens are not approved for babies < 6 months. So just cover up. Furthermore, there is no difference in sunscreen recommendations for children vs. adults. Use the same sunscreen for everyone. (Note, there are rare medical conditions where babies are extremely sun-sensitive and sunscreen use may be warranted.)

How much sunscreen should be applied?

2 mg/cm2 is the number used by the FDA to rate sunscreen SPF. This was the lowest amount that in the laboratory gave a uniform thickness on the skin. In practice however, most people put only half as much on as they should. This translates to about 1 ounce of a lotion for the entire body. If you are using a stick sunscreen, pass it over the skin at least 3-4 times. One study found that patients spend an average of 4.3 minutes applying sunscreen when they actually need 14 minutes!!

Sunscreen burns my eyes!

Try a stick sunscreen about the eyes

Are any sunscreens better for water sports?

Consumer Reports found the mineral sunscreens (zinc, titanium) less effective than the chemical sunscreens when you are in water.

Sunscreen Sprays

In general, try to avoid spray sunscreen. it is not known the consequences of breathing the spray into the lungs. Furthermore, most people don't use enough of the spray to provide adequate protection.

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