How Bad Is It Really to Use Expired Sunscreen?

You're about to head out for your first beach trip of the season when you realize something important: You forgot to buy sunscreen. Fortunately, there's an old bottle sitting in the back of the medicine cabinet. Is it OK to just grab that?

The answer depends on just how long it's been sitting there and what the storage conditions were like.

Sunscreen doesn't last forever, and using a product that's past its prime could spell bad news for your skin, warns Neil Farnsworth, MD, a board-certified dermatologist with Westlake Dermatology in Houston, Texas.

Here's how long sunscreen lasts, the possible effects of using expired sunscreen, how to know if your sunscreen is expired and tips to store your sunscreen bottle properly so it can give you the most effective protection.

The short answer is: Yes. Sunscreens are required by the Food & Drug Administration to provide the level of sun protection (SPF) listed on the bottle for three years. (This is true for both lotions and sprays.) After that, the product is no longer guaranteed to be stable and may not protect your skin from the sun's UV rays, and it's considered to be expired, Dr. Farnsworth says.

The expiration date — which is three years after the sunscreen has been manufactured — is typically listed on the sunscreen bottle or tube. But if it's not, you should write the date on the product when you buy it so you remember how old it is, the Mayo Clinic recommends.

Sunscreen's three-year shelf life means it's likely fine to use that half-empty bottle from last summer, provided it was stored correctly. Excessive heat or humidity can cause sunscreen to degrade faster, so a product that's been sitting in a glove compartment, hot garage or in direct sunlight may not last as long as the label promises, the Cleveland Clinic notes.

But there's one important thing to keep in mind: A single bottle of sunscreen should only last for a few days' worth of application if you're using the recommended amount (a shot glass' worth for the entire body) and reapplying as often as you should (every 90 minutes), Dr. Farnsworth points out.

So if you're out in the sun regularly and have sunscreen left over from a previous season, that could mean you're not using enough to really protect yourself.

The main problem with using expired sunscreen is that it puts you at risk for getting a sunburn.

Over time, that can increase your risk for skin cancer and cause your skin to age prematurely, according to the Skin Cancer Foundation.

"Once sunscreen is expired, it loses its efficacy and won't give you the protection you think you're getting," Dr. Farnsworth says.

That's especially likely for chemical-based sunscreens containing ingredients like avobenzone or octinoxate, which can break down quickly, according to the Cleveland Clinic.

That's not the only problem. Both chemical and mineral sunscreens contain dispersant ingredients that help a sunscreen spread evenly across your skin. But those dispersants may not work as well once the expiration date passes, which can change a sunscreen's consistency. That can make it harder to apply the sunscreen evenly and result in less thorough sun protection, the Cleveland Clinic adds.

It's also possible for expired sunscreen to oxidize or harbor bacteria, which could potentially trigger an allergic reaction, a rash or acne, per the Cleveland Clinic.

If your sunscreen has been stored at room temperature and out of direct sunlight, the best way to tell whether it's useable is to simply look at the expiration date, Dr. Farnsworth says.

But if there's no date on the bottle or it was stored somewhere hot or humid, you'll need to take a closer look at the sunscreen itself to tell whether it's still usable. Per Consumer Reports, there's a good chance your sunscreen is past its prime if:

• The sunscreen seems watery, dry or gritty
  
• The color has changed
  
• It smells "off"
  

Nobody wants to throw out a half-full bottle of sunscreen they just recently bought. To make sure yours stays potent, store it indoors at room temperature.

And keep it out of direct sunlight: When you're outside, stow your sunscreen in a shaded spot or wrap it in a towel, the Mayo Clinic recommends.

Expired sunscreen doesn't offer the same protection against the sun's UV rays, so if you use it, you could get a sunburn and increase your chances for skin cancer.

You'll set the stage for more wrinkles, too. "It can lead to increased skin damage," Dr. Farnsworth says. "It's not considered safe."

And old sunscreen could trigger a skin reaction that leaves you dealing with a burn and a rash at the same time — ouch.

Have more questions about your sunscreen's shelf life? We've got answers.

The ingredients in sunscreen start to break down after three years whether a product has been opened or not, according to Consumer Reports.

On the other hand, your sunscreen won't go bad faster once it's been opened, provided it's stored at room temperature and out of direct sunlight.

Yes, as long as the sunscreen was stored at room temperature and out of direct sunlight. Per FDA regulations, sunscreens are required to maintain their original strength for three years.

If you're not sure how the sunscreen was stored, check how it looks, smells and feels before using it. Any changes to the color, odor or consistency could mean it's expired, even if it hasn't passed its expiration date.

Mineral sunscreens tend to be gentler than their chemical-based counterparts, making them a better choice for sensitive skin, Dr. Farnsworth says. These are made with ingredients such as zinc oxide and/or titanium dioxide, which sits on top of the skin instead of being absorbed.