Cancer Treatment Centers of America

Understanding sunscreen

If you enjoy spending time outside in the sun, sunscreen is the best defense against skin cancer. Sunscreens use a combination of chemicals to stop the sun’s ultraviolet (UV) radiation from reaching your skin.

UVA and UVB are two types of ultraviolet radiation that can damage your skin. UVB rays cause sunburns, while UVA rays can lead to wrinkles and sagging, and intensify the carcinogenic effects of UVB rays. A simple way to remember the types of sun rays is UVA stands for “aging,” while UVB stands for “burns.”

What to look for in a sunscreen

With so many different types of sunscreens available, finding the right one for your needs can be confusing. Here are some important facts to consider when selecting and applying sunscreen.

Sun Protection Factor (SPF) – This indicates a sunscreen's ability to prevent UVB rays from damaging your skin, but does not account for UVA rays. The SPF number represents the amount of time it takes for your skin to redden, multiplied by the SPF number. If you burn after 10 minutes, SPF 10 means it will take 100 minutes for you to burn.

However, it can be difficult to gauge how long it takes for your skin to burn, and the true goal is to avoid burning all together. Therefore, dermatologists recommend sticking with an SPF of 15 or higher for appropriate sun protection. To protect against UVA rays, look for the following additional phrases on sunscreen bottles: multi spectrum, broad spectrum or UVA/UVB protection.

  • Sunblock vs. sunscreen – Sunscreen soaks into your skin and absorbs UV rays, while sunblock reflects or blocks the rays. Sunblock is usually stronger, but manufacturers can interchange the names to mean the same thing. If sunblock is what you want, look for ingredients like titanium dioxide, zinc oxide or avobenzone. These ingredients also provide additional protection against UVA rays, unlike the average sunscreen.
  • How to apply – Always apply sunscreen liberally about a half hour before going outside to allow it to soak in. Use about 1 ounce (the size of a shot glass) to cover your whole body. Reapply every two hours, or immediately after sweating heavily, swimming or wiping off your skin. Water-resistant sunscreens are available if you are active or plan to be in water, but reapplication is still necessary.
  • When to wear sunscreen – Ideally, sunscreen should be worn every day you plan to be outside. Even if there are clouds outside, UV rays can still break through.
  • Who should wear sunscreen – Everyone should wear sunscreen. While babies and people with fair skin may be more susceptible to burns, anyone can develop skin cancer. Even if you have dark skin or you’ve never been sunburned before, protecting yourself from the harsh rays of the sun by applying sunscreen or minimizing exposure is one of the best ways to prevent skin cancer.