What is sunscreen?
Sunscreens are products that help prevent the sun’s harmful rays from reaching the skin’s surface. The sun emits harmful rays that reach the earth’s surface. These ultraviolet rays are divided into two types: ultraviolet A (UVA) and ultraviolet B (UVB) rays. UVA rays are longer wavelength rays (320-400nm) that penetrate deep into the skins surface and are a major cause of skin aging and wrinkling. UVA rays can penetrate through glass windows and are the dominant tanning rays. It is now believed that UVA rays also contribute to the development of skin cancers. Whether exposure comes from outdoor sunlight or tanning parlor salons, UVA rays cause cumulative skin damage. UVB rays are shorter in wavelength (290-320nm) and are predominately the cause of skin reddening, sunburn and skin cancers. These rays cannot penetrate through glass windows. UVB rays also play a role in tanning and contribute to the development of fine lines, dark spots, and wrinkles.
What is SPF?
SPF stands for Sun Protection Factor. SPF indicates how much solar energy (ultraviolet radiation) is required to cause sunburn on an individual's skin when using sunscreen compared to the amount of solar energy required to cause sunburn on unprotected skin. Factors influencing the total amount of solar energy include, the amount of time in the sun, the time of day of sun exposure (an hour of sun exposure at 9:00 am may be equal to 15 minutes of solar energy obtained at noon), location, with greater intensity occurring at higher altitudes, and weather conditions, as clouds can absorb solar energy thereby making solar intensity greater on clear days. SPF is a relative measure of sunburn protection provided by sunscreens. As the SPF increases, so does the sunburn protection. An SPF of 30 prevents 97% of UVB rays from reaching the skin’s surface. An SPF of 50 prevents 98% of UVB rays from reaching the skin's surface. No sunscreen provides 100% protection.
What does “broad-spectrum” mean?
Broad-spectrum sunscreens provide protection from both UVA and UVB rays. When used as directed, these sunscreens will not only protect against sunburn, but also reduce the risk of skin cancer and premature skin aging. Sunscreen alone cannot protect the skin from 100% of the sun’s harmful rays; therefore, it is recommended to seek shade when outdoors, especially between 10:00 AM and 4:00 PM, and wear a wide-brimmed hat, long sleeves, and sunglasses when exposed to direct sunlight.
What does “water-resistant” mean?
Water-resistant sunscreen is a product that will maintain its declared SPF protection for a minimum of 40 minutes of water immersion. Products that claim to be water-resistant must state on the front label how many minutes of protection (based on standard testing) a user can expect to get of the declared SPF level while swimming or sweating. Two times will be permitted on labels: 40 minutes or 80 minutes.
Sunscreen vs. Sunblock?
Sunscreens can be classified into two categories depending on how they prevent the ultraviolet rays from reaching the skin. Chemical sunscreens contain ingredients that absorb the ultraviolet rays and prevent them from penetrating the skin. Each ingredient in chemical sunscreens can only filter a portion of the ultraviolet spectrum so most chemical sunscreens contain more than one active ingredient. Most chemical sunscreens break down after several hours of exposure to sunlight and must therefore, be reapplied frequently. Chemical sunscreens are often colorless and leave an invisible film on the skin after application. Chemical sunscreens are more likely to elicit an allergic reaction than physical blocks.
Physical sunscreens, often referred to as sunblocks (although the FDA no longer allows this term on sunscreen labels), are products that reflect and scatter the ultraviolet light. These products contain titanium dioxide and zinc oxide, which physically block ultraviolet radiation (UVR). Physical sunblocks are considered broad-spectrum sunscreens, as they protect against UVA and UVB rays. Physical sunblocks can leave a whitish appearing film on the skin after application but they are much less likely to cause allergic reactions.
FDA Approved Sunscreen Ingredients:
Active Ingredient/UV Filter Name
Ultraviolet Range Covered
UVA1: 340-400 nm
UVA2: 320-340 nm
UVB: 290-320 nm
Aminobenzoic acid (PABA)
Ecamsule (Mexoryl SX)
Enulizole (Phenylbenzimiazole Sulfonic Acid)
Meradimate (Menthyl Anthranilate)
Octinoxate (Octyl Methoxycinnamate)
Octisalate (Octyl Salicylate)
UVB, UVA2, UVA1