Ultraviolet light is invisible to humans, but the effects from exposure to it can be very apparent! With sun exposure, there are two main types of UV rays that cause damage to the DNA in your skin cells. With that being said, it’s important to protect yourself from both types of damaging UV rays. UV-A rays cause skin damage that result in not only tanning but also skin aging and wrinkles. It is important to buy sunscreen that lists “broad spectrum” on the label as it will protect from both UV-A and UV-B rays. UV-B rays cause sunburns and play a significant role in skin cancer. This is where the SPF, or sun protection factor, comes into play.
So what does the SPF number mean? It is a rating system that tells you what fraction of sunburn-producing UV rays will reach your skin. For example, “SPF 35” means that 1/35th or 2.86% of the UV rays will reach your skin. You might think that sunscreen with “SPF 70” would give you twice as much coverage, right? Not so much! Sunscreen with “SPF 70” would mean 1/70th or 1.42% of UV rays will reach your skin. Essentially, a “SPF 70” sunscreen would only have a 1.44% increase in protection from UV-B rays. Sunscreen with high SPFs not only offer marginal additional skin protection but can also be associated with increased prices as well as a false sense of security. This may lead to people staying out in the sun for longer, not reapplying as often, or not using other methods of sun defense. This in turn leads to more UV damage which is what we were trying to avoid in the first place!
When you’re getting a healthy dose of Vitamin D next time, the Skin Cancer Foundation recommends sunscreen of at least SPF 30 that is water-resistant and broad spectrum. In addition, apply sunscreen 30 minutes prior to going outside and reapply, at minimum, every 2 hours or after swimming or sweating. Don’t forget that sunburns never looked good on anyone so also protect yourself with clothing, wide-brimmed hats, sunglasses, and shade!