Does sunscreen expire?
Q: Does sunscreen expire?
The short answer: yes
The long answer: sunscreen usually lasts 1-3 years. There should be an expiration date on the bottle near the cap or on the bottom of the bottle. Other than that, it amazes me that people can have a bottle of sunscreen that has outlived its own expiration. Part of this comes from the tendency of some people to not use enough. Remember to apply a thick layer over the entire exposed part of your body.
Q: How long does the sunscreen work?
This is where the SPF is a factor. SPF measures how long you can stay in the sun. The basic formula is:
Time you can normally stay in the sun before burning multiplied by SPF. So if you can last 20 minutes in the sun normally, SPF 15 will be effective up to 300 minutes while SPF 30 will be effective up to 600 minutes.
There are many factors to consider here. Your skin tone will largely determine how well you tolerate the sun. Melanin is a photochemical that naturally protects the skin from UV radiation. It also adds pigmentation by darkening the skin. So realistically, the more protected you are from the sun, the darker your skin, but it’s much easier to say the other way around. The darker you are, the more protection you have.
Keeping your skin covered and staying in the shade also helps your sunscreen last longer. However, be careful with your clothing because you can easily remove the sunscreen as soon as you apply it. Sweat and water will also wear away most sunscreens, with the added downside that you could burn even faster while swimming. Water reflects a lot of light. It also cools you down so you don’t feel like you’re getting burned. Don’t be fooled, sunburns come from UV radiation, not heat, so water won’t save you.
The best sunscreen works to protect you against both UVA and UVB rays. READ THE LABEL and make sure not all products offer this. The difference is that UVA radiation penetrates deeper into the skin. It’s probably not as dangerous as UVB rays, but research is now beginning to show that both play a role in cancer. UVB rays are what cause your skin to burn.
There are many ingredients that may or may not be used in a particular sunscreen. Zinc oxide and titanium dioxide are some of the most common, and both protect against UVA and UVB rays.
Bottom line: If you have a bottle of sunscreen that’s been sitting around for years, just throw it away. Go buy a bottle with a high SPF like SPF30 or higher. Make sure it mentions both UVA and UVB rays. Apply generously and apply more throughout the day. If you plan on swimming, get one that is waterproof.
