What Is SPF (Sun Protection Factor)?

 

SPF, or Sun Protection Factor, is a measure that indicates the level of protection a sunscreen offers against UVB rays, which are primarily responsible for sunburn and contribute to skin cancer.

 

 

Understanding SPF:

1. Protection Level:

• The SPF number indicates how long you can theoretically stay in the sun without getting sunburned compared to not wearing sunscreen.
• For example, if you usually burn after 10 minutes in the sun, using an SPF 30 means you could stay protected for about 300 minutes (30 times longer), assuming proper application and no other factors like sweating or swimming.
• In other word, SPF  refers to how much UVB it allows in, not how much it blocks.
• Eg: A sunscreen with SPF 15 allows one-fifteenth of the sun's rays to reach your skin, or about 7%. So it filters out about 93% percent of UVB rays while SPF 30 (1/30)  filters about 97%.

 

2. Percentage of UVB Rays Filtered:
SPF also roughly corresponds to the percentage of UVB rays filtered:

• SPF 15 filters about 93% of UVB rays.
• SPF 30 filters about 97%.
• SPF 50 filters about 98%.

 

3. Limitations:

No sunscreen can provide 100% protection, and higher SPF numbers can lead to a false sense of security. It's essential to reapply every two hours and after swimming or sweating.

 

4. Broad-Spectrum vs. SPF:

SPF only measures UVB protection. For comprehensive protection, look for products labeled "broad-spectrum," which protect against both UVA and UVB rays.

Conclusion:

SPF is a vital factor in choosing sunscreen, but it’s equally important to apply it correctly and reapply regularly to ensure effective sun protection.