Sunscreen should be reapplied regularly for the best protection against sun damage.
SPF, or sunburn protection factor, measures a sunscreen's power to protect individuals from sunburn caused by exposure to solar energy. For example, a sunscreen with SPF 30 blocks approximately 97 percent of UVB radiation from the sun, according to the Skin Cancer Foundation. Using an SPF product is an important step in protecting against skin cancer and signs of premature aging, but a number of factors influence an individual's need for high SPF products.
Amount of Product Used
SPF is measured by the application of 2 mg of sunscreen to each square centimeter of skin. However, most consumers only apply 0.5 mg to 1 mg per square centimeter, according to the Skin Cancer Foundation. Applying a product with a higher SPF can offset this issue.
Solar Intensity
The sun's intensity at different times of the day and different locations affect a person's SPF needs. Solar energy is more intense during midday hours, at lower latitudes, on clear days and near reflective surfaces such as bodies of water, sand and snow. Skin should be protected with a high SPF product in these situations.
Skin Sensitivity
A person's skin tone and other sensitivities impact their SPF needs. Those who are fair-skinned, for example, absorb more solar energy than individuals with darker complexions. Photosensitivity, or increased sensitivity to the sun's rays, is a symptom of many medications that can also increase a person's risk of sunburn. These individuals can benefit from higher SPF products. Your doctor or pharmacist can provide more information on medications that cause photosensitivity.
Application
Regular application plays a major role in sun protection. No matter the SPF, a product's protection wears off within a few hours and can wash off sooner with water or perspiration. The FDA recommends applying a sunscreen with an SPF of at least 15 to all areas of uncovered skin daily. Sunscreen should be applied 30 minutes before sun exposure and reapplied every 1 ½ to 2 hours, or more often if you are swimming or sweating.
Other Considerations
Most sunscreens primarily protect against UVB rays, which cause sunburn. However, UVA rays, which contribute to skin aging and skin cancer, are also a concern. The Skin Cancer Foundation recommends choosing a product with SPF 30-50 that protects against both UVA and UVB rays. You should also take other precautions such as avoiding midday sun, seeking shade often when outdoors and wearing protective clothing like long sleeves, broad-brimmed hats and sunglasses.
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