How Does Sunscreen Actually Work?

We’ve all heard that wearing sunscreen is important. Sunscreen helps to block damaging ultraviolet A & B (UVA and UVB) rays, which can seriously impact our health and the health of our skin. UVA rays penetrate the skin more deeply, meaning they play a big role in skin aging (“What is” 2018). UVB rays, on the other hand, are the rays that can cause sunburn, and they can ultimately cause skin cancer (“What is” 2018). Understanding more about UVA and UVB rays highlights the importance of sunscreen. Today, we’re exploring how sunscreen actually works, and how you can use it properly to maintain your skin’s health and appearance.

Types of Sunscreen & How They Work

Did you know that there are two types of sunscreen? Sunscreen is either a physical sunscreen, or a chemical sunscreen. Physical sunscreen, as the name suggests, acts as a physical barrier to block UVA and UVB rays (“The Science” 2021). Physical sunscreen is mineral based, making it a very safe and effective choice for blocking harmful UV rays. Physical sunscreen is typically only available in lotion form, and will have a fairly thick consistency. Chemical sunscreen creates a chemical barrier - when the sunscreen is exposed to sunlight, a chemical reaction occurs, and the sunscreen then absorbs UVA or UVB rays and converts them to heat to prevent skin damage (“The Science” 2021). There is some controversy surrounding the safety of chemical sunscreens, but it’s important to note that no studies have proven them to be unsafe. Chemical sunscreens come in both liquid and spray forms (spray sunscreen is easier to inhale, so keep that in mind).

Sunscreen Use Guide

Experts recommend using sunscreen that’s at least SPF 50. Sunscreen isn’t a “set it and forget it” thing - sunscreen needs to be reapplied about every 2 hours to maintain UV protection (“How to choose” 2015). I don’t know about you folks, but I am definitely not reapplying every two hours - but I will from now on! If you’re swimming or planning on doing any sweat-heavy activities, be sure to purchase a water-resistant sunscreen. Water-resistant sunscreens will say on the label how often they need to be reapplied after water exposure.

References:

Harvard Health Publishing. (2015, July 9). How to choose and use sunscreen. Harvard Health. https://www.health.harvard.edu/cancer/how-to-choose-and-use-sunscreen.

Harvard Health Publishing. (2021, February 15). The science of sunscreen. Harvard Health. https://www.health.harvard.edu/staying-healthy/the-science-of-sunscreen.

University of Iowa. (2018, October 9). What is the difference between UVA and UVB rays? University of Iowa Hospitals & Clinics. https://uihc.org/health-topics/what-difference-between-uva-and-uvb-rays.