Sun Protection Factor

The Sun Protection Factor (SPF) is a number that indicates the effectiveness of a sunscreen in protecting the skin against damage caused by ultraviolet (UV) radiation from the sun. The higher the SPF number, the greater the protection against sun damage. Here are some explanations about SPF and how it should be applied: 

1. Meaning of SPF: 

– SPF primarily measures protection against UVB rays, which are responsible for sunburn. However, there is also a correlation with protection against UVA rays, which contribute to premature skin aging. SPF 15 blocks about 93% of UVB rays, while SPF 30 blocks about 97%. As the SPF increases, the percentage of additional protection increases more gradually. 

2. How to calculate protection: 

– The protection provided by SPF is calculated as follows: if your skin would normally burn after 10 minutes of sun exposure without sunscreen, an SPF 15 would provide protection equivalent to being in the sun for 15 times as long without burning (in this case, 150 minutes). 

3. Proper application: 

– You should apply sunscreen evenly over all exposed areas of skin. Be sure to cover the skin completely and don’t forget areas such as the ears, neck and feet. 

4. Sufficient amount: 

– It is recommended to apply at least 2 milligrams of sunscreen per square centimeter of skin. In practice, this means that for an average adult, approximately one ounce (30 milliliters) of sunscreen is needed to cover the exposed body. 

5. Frequency of application: 

– You should apply sunscreen at least 15-30 minutes before sun exposure and reapply every 2 hours, or more frequently if you are swimming or sweating. It is also advisable to reapply after towel drying. 

6. Reapply after water: 

– If you are swimming or doing activities that involve water, it is important to reapply sunscreen after getting out of the water, as water can wash some of the product away. 

7. Daily use: 

– Even if you are not planning to spend a lot of time in the sun, it is advisable to use sunscreen daily, as cumulative exposure over time can contribute to skin damage. 

Remember that proper use of sunscreen is essential to protect the skin against sun damage and reduce the risk of sunburn, premature aging and skin cancer.