About Sunscreens

What are sunscreens?
A primary goal of sun protection is the prevention of sunburns, but that is not its only goal. Incremental damage to the body occurs with each exposure to UV radiation, even exposure that does not produce redness or burning. This damage is cumulative with time and the magnitude of exposure. Over the years, total time in the sun is reflected by wrinkles, blotchy pigmentation, and with enough exposure, skin cancer.

Chemical sunscreens block the penetration of UV radiation through the epidermis by acting as filters and absorbing and reflecting high-energy UV. The sunscreen molecules absorb high energy UV photons, but a certain amount of UV light will enter the epidermis -- as no chemical sunscreen blocks 100 percent of all UV radiation.

What is the difference between a sunscreen and a sunblock?
The terminology used on sunscreen labels can be confusing. The protection provided by a sunscreen is indicated by the SPF listed on the product label. A sunblock is considered to be any sunscreen with an SPF of 15 or more. In theory, sunscreens protect an individual during an incident of UVB radiation exposure according to the following:

• SPF 15 sunscreen may absorb more than 92 percent of UVB radiation.

• SPF 30 sunscreen may absorb 96.7 percent.

• SPF 40 sunscreen may absorb 97.5 percent of UVB radiation.

What does SPF mean?
SPF value of a sunscreen is defined as the ratio of the energy required to produce a minimal erythema dose (skin reddening or minimal sunburn) through the sunscreen, compared to the energy required to produce the same reaction in the absence of the sunscreen.

For example, an individual who burns after 30 minutes of sun exposure could, in theory, extend the period of time until a burn begins to two hours with an SPF 4 sunscreen. However, the same person using a sunscreen with an SPF of 30 (15 hours of theoretical burn protection) may not in fact be protected from UV-induced erythema for an entire day of continuous sun exposure.

What about the chemicals in sunscreens?
The majority of the commercially available sunscreens today are a combination of agents from several chemical groups.

• Para-aminobenzoic acid (PABA) was an early chemical sunscreen agent frequently associated with contact and sun-contact sensitivity reactions, had poor consistency, and often discolored clothing. It is rarely found in sunscreens today.

• Para-aminobenzoic acid esters (primarily octyl dimethyl para-aminobenzoic acid) are commonly used in many sunscreens and have not been associated with the problems of PABA.

• Other sunscreen agents include compounds from these groups:

• salicylates - these are weak UV absorbers, but are highly water insoluble and sensitivity is rare. The most widely used salicylates are homosalate and octyl salicylate. Salicylates are considered to be among the safest sunscreens, even when used in high concentrations.

• cinnamate

• benzophenone

• anthranilate

• dibenzoylmethane

How to use sunscreens:
A sunscreen protects from sunburn and minimizes suntan by reflecting UV rays. Information in the parentheses refers to the UV Index.

• Use of a sunscreen with SPF of 20 to 30 offers substantial protection from sunburning and usually permits no tanning. (for Index 7 and above)

• Choose a broad spectrum sunscreen that filters out UVA and UVB. (for Index 3 and above)

• A sunscreen that provides an SPF under 4 offers the least protection. If you rarely burn and always tan this level of skin protection may be sufficient to help prevent burning and uneven coloration. (for Index 3 and above)

• High SPF sunscreens protect from burning for longer periods of time than do sunscreens with lower SPFs. (for all index levels)

• Apply sunscreens to all exposed areas of skin including those easily overlooked areas such as the rims of the ears, the lips, the back of the neck, and the feet. (for Index 3 and above)

• Sunscreens are recommended for everyone (over six months of age) because all skin types need protection from solar ultraviolet rays. Lighter skin types are at the greatest risk of developing skin cancer; but all people are at some risk. Wrinkling, toughening, and aging will happen to all skin types. (for Index 7 and above)

• Apply sunscreen liberally. Recommended dose is 1 ounce per application. Reapply every two hours, after being in the water, or after exercising or sweating. Incidental time in the sun could add up to a sunburn. Don't forget the time spent walking your dog, window shopping, or jogging on your lunch hour. (for Index 7 and above)

• Don't forget the sunscreen when performing outdoor chores. (for Index 3 and above)

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