Protecting Your Skin: Everything You Need to Know About Sunscreen but Probably Don't

May is Skin Cancer Awareness Month, a vital time for residents of La Jolla to audit their sun protection habits. While most people know that sunscreen is necessary, many do not realize that skin cancer is the most common cancer in the United States. According to the American Academy of Dermatology, approximately one in five Americans will develop skin cancer in their lifetime. At coastal medical and cosmetic dermatology, we want to ensure you have the technical knowledge to choose the right protection for your lifestyle.

Decoding broad-spectrum and spf ratings

The term "broad-spectrum" is the most important label on your sunscreen bottle. It signifies that the product protects against both UVA and UVB rays. UVA rays are primarily responsible for premature skin aging and wrinkles, while UVB rays cause sunburns. Both contribute significantly to the development of skin cancer.

The SPF (Sun Protection Factor) rating specifically measures protection against UVB rays. While SPF 30 is the clinical baseline, Healthline notes that SPF 30 blocks about 97% of UVB rays, while SPF 50 blocks 98%. No sunscreen blocks 100% of UV radiation. The key to effectiveness is not just the number, but the volume and frequency of application. Most adults require a full ounce—roughly the size of a shot glass—to cover the entire body.

Mineral vs. chemical filters

Understanding the difference between active ingredients is essential for those with sensitive skin or specific environmental concerns. Chemical sunscreens work like a sponge, absorbing UV rays, converting them to heat, and releasing them from the skin. Common ingredients include avobenzone and oxybenzone. These formulas are popular because they are often sheer and easy to wear under makeup.

Mineral sunscreens, also known as physical blockers, use zinc oxide or titanium dioxide to sit on top of the skin and reflect UV rays like a shield. Cleveland Clinic highlights that mineral sunscreens are often better for those with rosacea or eczema because they do not trap heat in the skin. Recent studies from the last five years also indicate that mineral filters are generally considered more environmentally friendly for marine ecosystems.

The reality of reapplication and expiration

A single morning application is rarely enough for a day at the beach in La Jolla. Sunscreen filters break down upon exposure to direct sunlight and are easily washed away by sweat or water. You should reapply every two hours, or immediately after swimming or heavy perspiring.

It is also important to check the expiration date on your products. The active ingredients in sunscreen are unstable and lose their efficacy over time. If your bottle has been sitting in a hot car or has passed its three-year shelf life, it may no longer provide the SPF listed on the label. Protecting your skin is a year-round commitment that requires the right tools and consistency. We invite you to call coastal medical and cosmetic dermatology or visit our website to schedule an appointment for a comprehensive skin cancer screening or a personalized product consultation.