Everyone knows that regular application of sunscreen is your best defense against skin damage and skin cancer. Broad-spectrum sunscreens with a Sun Protection Factor (SPF) of 30 or higher are best—they block harmful UVA and UVB rays—and should be reapplied every two hours. And not just on your face, but everywhere you're exposed to the sun.

Despite its ease of use, there are still some myths about sunscreen that persist. Before you head out to enjoy these warm summer months, take a look at a few common misconceptions about using skin protection.

1. Myth: You’re probably using enough sunscreen.

Maybe you are, but there’s a good chance you’re not. According to the American Academy of Dermatology Association, most people apply just 25 to 50 percent of the recommended amount of sunscreen. You should be using a shot glass-full—about 1 ounce—to effectively cover your entire body.

2. Myth: Sunscreens can be waterproof or sweat-proof.

After slathering on sunscreen, you can dive into the pool and focus on your backstroke, utterly unconcerned with your waterproof protection washing off. Right? Wrong. Sunscreen can be water-resistant, meaning it won’t wash off as easily as regular sunscreen, but it’s not waterproof or sweat-proof. Companies were required to stop using that term by the Food and Drug Administration (FDA) in 2011. To be “water-resistant,” it has to remain effective while you get in and out of water over a 40-minute period (or 80 minutes for "very water-resistant" products). Still, it’s best to reapply sunscreen after getting out of the water, sweating, or toweling off to ensure its effectiveness.

3. Myth: The SPF in makeup is enough.

Cosmetics with sunscreen blended in sometimes prompt people to pass up any additional protection. That’s not a good idea. For one thing, the makeup might not be broad-spectrum, protecting against both UVA and UVB rays; it might also have an SPF of less than 30, which isn’t enough to protect effectively (many dermatologists recommend 30 and higher). Additionally, using makeup and sunscreen on just your face leaves the rest of your body vulnerable. It’s best to double up, using sunscreen on any exposed skin in addition to anything cosmetic on your face.

4. Myth: Sunscreen and sunblock are the same thing.

Nope. Sunscreen works chemically by filtering the sun’s UV rays, converting them into heat released by the skin, while sunblock creates a physical barrier using titanium dioxide and zinc oxide, reflecting them instead. (Think of a lifeguard with a swatch of white lotion on their nose.) The FDA ruled in 2011 that sunscreens cannot be labeled as sunblock because of this difference. Both are effective, but sunscreen may work better if you plan to be active (and sweating) and are concerned about your appearance. Chalky-white sunblock is not always Instagram-friendly.

5. Myth: Sunscreen is good forever.

Not exactly. Although the FDA mandates that sunscreens remain effective for three years after manufacturing, some may not have expiration dates visible on the packaging. If you’re not sure when you bought your sunscreen, it’s best to get a new bottle. And if you need a new bottle, there’s a good chance you’re not using it nearly as often as you should. According to the FDA, using the proper amount of sunscreen means you’ll be running out long before you get concerned about it being out of date.

6. Myth: You need sunscreen only in the summer.

UVA and UVB rays certainly come on strong in summer, but they’re present anytime the sun is out—even in winter. All the snow and ice can refract the UV rays, and the damage they can cause isn’t influenced by the temperature outside. If you’re going to be outdoors for any length of time, apply sunscreen to the exposed areas of your skin—face, neck, and hands.