By Jason Barbaria
According to the American Cancer Society, more than 2 million people are diagnosed with skin cancer in the United States each year. There are more than 2,000 over-the-counter sunscreen formulas on the market today. How can you tell which sunscreens are the safest, most effective, and represent the best value for your money? In most cases, the answer comes down to the difference between the two types of filtering ingredients. Here's what you need to know.
Chemical or Physical?
The UV radiation in sunlight consists of UV-A, UV-B, and UV-C rays. UV-A and UV-B are both responsible for photoaging, skin cancer, sunburn, tanning, and wrinkling. UV-C is not a factor in skin health, as it is absorbed by the Earth's atmosphere and does not reach us in significant amounts. Broad-spectrum sunscreen protects against both UV-A and UV-B. This protection can work in one of two ways: chemical or physical.
Chemical UV Filters
- Work by absorbing UV radiation;
- Require application 30 minutes before sun exposure;
- Provide partial protection from UV spectrum;
- May irritate the skin and eyes;
- Not regulated for safety by the US Food and Drug Administration (FDA)--some may even be carcinogenic;
- Not photostable (exposure to sunlight degrades effectiveness);
- Avobenzone is the most commonly used chemical filter ingredient.
Physical UV Filters
- Work by reflecting UV radiation;
- Start protecting immediately upon use;
- Provide full broad-spectrum protection;
- Non-irritating to skin and eyes;
- Safe, as particles do not penetrate the skin;
- Highly photostable (exposure to sunlight does not change effectiveness).
- Zinc oxide and titanium dioxide are the most commonly used physical filter ingredients. Clothing and shade structures also count as physical filters.
Jason Barbaria is director of marketing at Dermagenics, a skin care line that includes sunscreen, cleansers, and moisturizers.