Part 11/14:
Sunscreens act as a barrier, absorbing, reflecting, or deflecting harmful ultraviolet (UV) rays. They are rated by SPF (Sun Protection Factor), measuring their effectiveness against UVB rays—the primary cause of sunburn and DNA damage leading to skin cancer.
Interpreting SPF:
An SPF 30 sunscreen theoretically allows 1/30th (about 3.3%) of UVB rays to reach the skin.
This means it blocks approximately 97% of UVB rays.
Higher SPF values (e.g., 50 or 100) provide marginally increased protection—blocking about 98% to 99%.
Choosing the Right Sunscreen
Dr. Young recommends:
SPF 40-50 for most daily activities.
Higher SPF (such as 50+) for prolonged outdoor activity or UV-sensitive conditions like melasma.