Sunscreen
Sunscreen works by combining organic and inorganic active ingredients. Inorganic ingredients like zinc oxide or titanium oxide reflect or scatter ultraviolet (UV) radiation. Organic ingredients like octyl methoxycinnamate (OMC) or oxybenzone absorb UV radiation, dissipating it as heat. Some sunscreens protect us from the two types of damaging UV radiation: UV-A and UV-B. Both UV-A and UV-B cause sunburns and damaging effects such as skin cancer.
Ultraviolet radiation is broken into three types of wavelengths:
- UV-A: This is the longest wavelength and is not absorbed by the ozone. It penetrates the skin deeper than UV-B.
- UV-B: Responsible for sunburns. It is partially blocked by the ozone layer.
- UV-C: This is totally absorbed by the earth's atmosphere; we encounter it only from artificial radiation sources.
When
purchasing sunscreen, the Sun Protection Factor or SPF measures
how effectively the sunscreen formula limits skin exposure to UV-B
rays that burn the skin. The higher the SPF the more protection
the sunscreen will provide against UV-B rays. SPF does not measure
UV-A. If you are looking for UV-A protection, the experts recommend
that you purchase a product that has broad-spectrum protection. Library of Congress
When To Apply Sunscreen
- Apply sunscreen approximately 30 minutes before being in the sun (for best results) so that it can be absorbed by the skin and less likely to wash off when you perspire.
- Remember to reapply sunscreen after swimming or strenuous exercise.
- Apply sunscreen often throughout the day if you work outdoors, and wear hats and protective clothing.
How To Apply Sunscreen
- Shake well before use to mix particles that might be clumped up in the container. Consider using the new spray-on or stick types of sunscreen.
- Be sure to apply enough sunscreen. As a rule of thumb, use an ounce (a handful) to cover your entire body.
- Use on all parts of your skin exposed to the sun, including the ears, back, shoulders, and the back of the knees and legs.
- Apply thickly and thoroughly.
- Be careful when applying sunscreen around the eyes.
What To Look for When You Buy Sunscreen
- Pick a broad-spectrum sunscreen that protects against UV-A and UV-B rays and has a sun protection factor (SPF) of at least 15.
- Read product labels. Look for a waterproof brand if you will be sweating or swimming. Buy a non-stinging product or one specifically formulated for your face.
- Buy a brand that does not contain para-aminobenzoic acid (PABA) if you are sensitive to that ingredient.
- Try a sunscreen with different chemicals if your skin reacts badly to the one that you are using. Not all sunscreens have the same ingredients.
- Use a water-based sunscreen if you have oily skin or are prone to acne.
- Be aware that more expensive does not mean better. Although a costly brand might feel or smell better, it is not necessarily more effective than a cheaper product.
- Be aware of the expiration date because some sunscreen ingredients might degrade over time. CDC
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