By Gary M. White, MD
FDA Rules for Sunscreen
- SPF max 50.
- No product can say sunblock.
- The term broad-spectrum means the critical wavelength is equal to or greater than 370 nm (well into UVA band). The critical wavelength is the wavelength below which, 90% of the area under the curve lies (when graphing absorbance vs wavelength).
- Sunscreens with SPF => 15 and that are broad-spectrum can claim on their labeling that they help prevent sunburn, skin cancer, and skin aging.
- Sunscreens with SPF < 15 and/or not broad-spectrum can only say that they help prevent sunburn.
AAD Guidelines for Preferred Sunscreen
- SPF >= 30
- Broad-spectrum coverage
- Water resistant for 40-80 minutes.
- Actinic keratoses
- Squamous Cell carcinoma
- As of this writing, there is very little evidence to show that sunscreen use reduces BCC.
Sunscreens are not approved for babies < 6 months. So just cover up.
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. For a spray, spray it on until the skin glistens and then use your hand to make sure it is uniformly distributed.
Sunscreen burns my eyes!
Try a stick sunscreen about the eyes (e.g. MDSolarSciences Natural Mineral Sunscreen Stick SPF 40).
If current trends continue, sprays will soon overtake lotions as the primary sunscreen formulation. Spray sunscreens are as efficacious as lotion sunscreens when applied correctly in a laboratory setting [JAAD 2012;67:1220–1227]. The problem is that in real life, consumers often gets less on the skin than is needed.
Are some sunscreens better than others?
For patients with specific skin diseases that are provoked by the sun, e.g. melasma, polymorphous light eruption, lupus, etc, the daily uses of a tinted, physical block sunscreen is best. Believe it or not, visible light--not just ultraviolet light--can cause/aggravate some of these conditions. Thus, it is very important to apply a tinted, physical block sunscreen (i.e. contains titanium dioxide, zinc oxide, or iron oxide) immediately upon wakening and several times a day. Some feel the iron oxide-containing sunscreens are closer to the skin color of darker-skinned individuals.
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