Sunscreens are important skin-care products used to prevent photoaging and skin cancer. Until recently it was believed that blocking UVB radiation and sunburn were the only measures needed to prevent sun damage. The SPF rating was developed to measure the ability of a sunscreen to block UVB radiation.
Now we know that UVA radiation also damages the skin. Although the FDA has proposed a rating system that lets you know how well a sunscreen blocks UVA, that proposal has not been approved yet. Unfortunately the only way to know about the UVA-blocking ability of a sunscreen is to look for at least one of these ingredients.
AvobenzoneAvobenzone (Parsol 1789) is the only chemical that absorbs the whole UVA spectrum from 310-400 nm. It does not provide any UVB absorption. The problem with avobenzone is that it breaks down in sunlight. As a matter of fact, 50-90% of this sunscreen is lost 1 hour after exposure to sunlight. Some of the UVB absorbers like OMC and octocrylene make avobenzone much more stable.
- Advantages: Blocks full UVA spectrum and does not cause skin irritation
- Disadvantages: Breaks down quickly in sunlight unless combined with certain UVB blockers
BenzophenonesThe benzophenones, oxybenzone and dioxybenzone, are a mixed bag of good and bad properties. They are a common ingredient not only in sunscreens, but also in UV protective fabrics. They are good UVA absorbers but they also absorb in the UVB range. The benzophenones aren't as irritating as PABA but oxybenzone is the most irritating of all the sunscreen ingredients on the market now.
- Advantages: Blocks a broad spectrum of UV radiation including UVA
- Disadvantages: Irritating and not water resistant
HelioplexHelioplex is a proprietary formula by Johnson & Johnson Neutrogena. This new formulation is a combination of several different UVA and UVB blockers plus stabilizers that keep the more sun-sensitive ingredients from breaking down. It is a good, broad-spectrum sunscreen that is not irritating. It comes in SPF's of 55, 70, and 85. The active ingredients in Helioplex with their concentrations are:
- Avobenzone (3%)
- Oxybenzone (6%)
- Octocrylene (2.8%)
- Homosalate (10% in SPF 55 and 15% in SPF 70)
- Octisalate (5%)
Mexoryl SXThe other names for this compound include terephthalylidene dicamphor sulfoic acid (TDSA), ecamsule, and Anthelios SX. L'Oreal Paris developed mexoryl and it has been used in Europe since 1982. In 2006 the FDA approved its use in the United States. It is combined with avobenzone and octocrylene and marketed in the US by La Roche Posay as Anthelios SX. This sunscreen is a broad-spectrum blocker that is water resistant, very stable in the sun, and not irritating to the skin. The active ingredients in Anthelios SX with their concentrations are:
- Ecamsule (2%)
- Avobenzone (2%)
- Octocrylene (10%)
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