Cherry Street Pharmacy
Cherry Street Pharmacy

Sunscreen by the Numbers

The SPF numbers on the sunscreen at your local pharmacy may be a little misleading. You may even be using the wrong sunscreen for your skin or the activities you are going to participate in. Here, we learn about sunscreen, the harmful rays of the sun and what they can do, as well as what SPF numbers mean.

What are UVA and UVB rays?

There are two forms of UV rays that we look at when it comes to sunscreen. Most sunscreens only block UVB rays unless you find one at your pharmacy labeled “broad spectrum” so it blocks both. UVA rays cause longer-term damage to your skin, causing premature aging or even cancer. UVB rays, on the other hand, are what cause the itchy and painful sunburns we’ve all experienced.

What does SPF on the bottle at the pharmacymean?

The SPF label on your sunscreen tells you how many damaging UVB rays are absorbed by the skin. It stands for “sun protection factor.” However, it can be misleading to say that the higher the number, the longer you can stay in the sun. To calculate that, you will need to know how long you can usually stay in the sun without sunscreen and the SPF of the sunscreen you are using. Multiply both numbers and find the number of minutes you can stay in the sun.

How are SPF numbers calculated?

All new sunscreens must be tested to find their true SPF. Up to 20 testers are used to figure this out. These testers are usually very sensitive to the sun, so the results are more accurate. During this test, they will calculate how much UV it takes to cause a burn. Then they test again with the sunscreen in question, usually not one you can find at your pharmacy yet. They use these numbers to calculate the true SPF of the sunscreen.

What is UVB absorption?

UVB rays are the ones used to calculate the SPF of a given sunscreen. However, once you are at your pharmacy to pick some up, it may not be beneficial to grab the one with the highest SPF. While SPF ratings can go as low as 2, the amount of UVB rays deflected doesn’t increase exponentially with the increase in SPF rating. Anything 30 SPF or higher will keep you from absorbing over 90% of the UVB rays.

How do you use sunscreen?

Make sure you are applying sunscreen at least 15 minutes before you will be exposed to the sun, so it has time to be fully effective. You will have to do this with nearly every sunscreen you find at the pharmacy. You also want to reapply sunscreen after being in water or sweating, even if it says it is waterproof or sweatproof. And don’t forget the commonly missed places when applying sunscreen: the tops of the feet, the ears, the back of your neck, and your ears.

If you want to get the most out of the sunscreen you find at your local pharmacy, it is important to know just what SPF means and how it can protect you from harmful UVB rays. Don’t forget to look for a broad- spectrum sunscreen that protects against UVA rays as well.

The information on this website is for general information purposes only. Nothing on this site should be taken as an advice for any individual case or situation.

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