The answer from the Food & Drug Administration is pretty clear: All shelf-stable products, including sunscreen products, typically have a life of three years from their manufacturing date. This can be tricky to remember since most brands conceal expiration info in a light-colored font on their bottle. When in doubt, Marnie Nussbaum, MD, FAAD, a board-certified dermatologist, recommends writing the date you purchased that best sunscreen on the bottle with a permanent marker so you can keep up with the three-year time frame. Though three years seems like a reasonable enough period in which to use up a bottle of sunscreen, it’s not without caveats. How well you take care of your sunscreen, where you store it, and how often you apply a layer all play a factor, too. Here, dermatologists provide the 411 on sunscreen expiration and when you should go ahead and recycle the bottle. In other words? Here’s when to toss it:

If Sunscreen Appears Separated

While all sunscreens can separate from their base, the appearance changes based on what formula you’ve selected. There are two types of sunscreens on the market: chemical sunscreens and those with mineral-based ingredients. If you squeeze the tube of a chemical sunscreen, and it comes out as a white clump surrounded by water and oil, give it a quick shake and try again, says Tsippora Shainhouse, MD, FAAD, a board-certified dermatologist. If it still comes out looking like salad dressing, it’s time to recycle the bottle. Mineral sunscreens, which until 2013 were called sunblocks and contain zinc oxide and titanium dioxide, may take longer to lose their form. “These are much more shelf-stable, but once combined with other chemicals and base ingredients to improve cosmetic elegance, these sunscreens can also expire," says Dr. Shainhouse.

If It’s Clumpy

Think about the dairy section of your go-to grocer when you analyze the consistency of your sunscreen. You should always have a formula that looks like cream cheese—not cottage cheese. Any clumpy, watery, grainy, or oily texture is a clear sign it’s time to toss. “It’s likely that the base is what’s breaking down,” Dr. Shainhouse says. “But you can’t know if the protective ability of the sunscreen chemicals has broken down, as well, making it ineffective.”

If It Smells

For many people, catching a whiff of sunscreen will bring them straight back to the glory days of summer, sailing on the sea, jumping in the pool, or going for one hike after another. So if you snap open your product and it doesn’t smell great? Dr. Shainhouse says it could be because of bacteria growing inside (yuck!) or the breakdown of chemicals within the base. “Because you can’t know if the protective sunscreen chemicals have deteriorated, it’s best to toss out this bottle and splurge for a new one,” she says.

If Your Bottle Has Been Compromised

Say your pup got ahold of your sunscreen, and now there’s a big hole in the bottle. Though it can be frustrating, especially if it’s a new bottle, Dr. Shainhouse says any damage to the exterior is reason enough to throw it out. Whether it was Fido’s fault, or the bottle is simply brittle or cracked, opt to toss and replace.

If You Left It Open Overnight

According to Dr. Nussbaum, when the sunscreen is open too long, it can allow bacteria to build up inside. This weakens the lotion, so it can’t offer the sun protection we need.

If the Color Looks Different

Sunscreen should be mostly white or mostly opaque, says Dennis Gross, MD, a dermatologist and dermatologic surgeon. So when you see shades of yellow or off-white, it could be an indication that your product has faded. “There is a possibility that the sunscreen is no longer at the same potency, so wearing it could leave you open to sun damage and at a higher risk for skin cancer,” Dr. Gross says.

If You Keep It in a Wet, Warm Place

Sunscreen’s three-year shelf life is based on the premise that you are storing it in a cool, dry place, according to dermatologist Erum Ilyas, MD, MBE, FAAD. If you keep it somewhere warm or wet, the sunscreen will lose its potency much more quickly.

If the Tube Is Empty (and It Should Often Be Empty!)

Honestly? You should never have to wonder if your sunscreen has expired. It should be easy to go through an entire bottle in a few weeks, particularly in the summer or on an outdoors-intensive vacation. As Ashley Magovern, MD, a board-certified dermatologist, puts it, if you’re following all of the sun protection rules, you’ll likely go through several bottles on vacation and be through your stash by the time fall arrives. So how much is enough? Dr. Magovern says a good rule to follow is one ounce per application for the body, which looks like a shot glass-full or a golf-ball-size dollop. You’ll probably need one-fourth of that for your face, so a few dime-sized proportions should do.