Sunscreen Dos and Don’ts: When to Apply, How Much to Use, and More

A bad sunburn can ruin even the best moments. Between the pain and the peeling, it can be days—a week even—before your skin returns to normal. Discomfort aside, excessive UV exposure can damage your DNA. And that’s always bad news.

To avoid all this, it’s best to slather on some sunscreen. Easy enough, right? Well, sort of.

When it comes to choosing sunscreen, the options may be overwhelming. Between active ingredients, SPF ratings, and so much more, there’s a lot to unpack. But don’t worry, we’ll break it down for you.

Why Use Sunscreen: The Dangers of UV Rays

Avoiding the discomfort of a sunburn is all the motivation most of us need to wear sunscreen. But sunscreen isn’t just about preventing sunburns. It’s about protecting your skin to keep it healthy and happy throughout your life.

Fun in the sun has many benefits. Sunshine helps you get the vitamin D you need, can boost your mood, and may even help reduce stress. But the effects of the sun aren’t all positive. The sun emits two types of ultraviolet (UV) rays—UVA and UVB—that can damage your skin. UVB rays, which have a shorter wavelength than UVA rays, are responsible for sunburns. UVA rays don’t cause burns, but they penetrate more deeply into skin cells. Both types cause DNA damage, which may lead to genetic mutation.

Brief exposure to UVA and UVB rays probably won’t cause noticeable skin damage, but over time these rays can damage skin cells and age your skin prematurely. As skin ages it loses elasticity causing wrinkles and creases to form—UV exposure may accelerate this process.

So how can you avoid this? Shutting yourself in your house isn’t exactly practical, and thankfully it’s not your only option. With a little bit of preparation—and a lot of sunscreen—you can enjoy the sun’s benefits while still protecting your skin.

Types of Sunscreen

There are two main types of sunscreen on the market: mineral (also called physical) and chemical. Both types of sunscreen protect your skin from the sun’s UV rays, but they achieve this in different ways. Let’s take a look at each:

  • Mineral sunscreen: Mineral or physical sunscreens typically have one of two active ingredients: titanium dioxide or zinc oxide. They sit on your skin’s surface and block UV rays from entering. In other words, they act as a physical barrier or shield to protect your skin. Mineral sunscreens used to be thick, leaving the skin with a visible white sheen after application. Nowadays, sunscreen manufacturers use nanoparticles (larger, broken up particles) in their sunscreen ingredients to help lessen this effect. Some sunscreens even add a tint to reduce this sheen even more.
  • Chemical sunscreen: Rather than blocking the sun’s rays, chemical sunscreens absorb them. When you’re in the sun, a chemical sunscreen lets UV rays enter, but a chemical reaction converts the harmful UV light into heat which is released off your skin. The ingredients typically found in this type of sunscreen are avobenzone, aminobenzoic acid, octocrylene, octisalate, and oxybenzone.

At this point, you probably have one big question: which type of sunscreen should I use? That depends.

Neither chemical nor mineral sunscreen is inherently better than the other. Both achieve the primary goal of sunscreen: preventing UV rays from damaging the skin for a period of time. There are, however, a number of pros and cons of each to consider.

Some of the chemicals used in chemical sunscreen—especially oxybenzone—have received negative press due to safety concerns. With that said, more research is needed to determine if these ingredients are actually harmful. And for now, they remain cleared by the FDA.

Another concern with chemical sunscreen is skin allergies. For people with sensitive skin and certain skin conditions (melasma and rosacea), its ingredients can cause allergic reactions or make existing skin conditions worse. If you experience these side effects, try switching to a chemical sunscreen with different active ingredients or move to a mineral sunscreen. Chemical sunscreens also do not offer immediate protection—they take 20–30 minutes to absorb into the skin before offering sun protection.

If you’re worried about exposing your skin to the ingredients in chemical sunscreen, mineral sunscreen is probably a better fit for you. Its two main ingredients—zinc oxide and titanium dioxide—have been approved by the FDA for decades. And as mentioned above, it can be better for sensitive skin.

Because it sits on top of the skin, mineral sunscreen doesn’t have to be absorbed to be effective, meaning it gives you immediate UV protection after it’s applied. But this form of  sunscreen also has its drawbacks. As it sits on your skin, it may clog your pores to contribute to or exacerbate acne breakouts. And let’s face it, nobody loves the white sheen of sunscreen—something that’s much more common with mineral sunscreens.

What is SPF: Demystifying Sunscreen Strength

One of the most commonly misunderstood aspects of sunscreen is SPF. This rating, a number shown on the front of most sunscreen bottles, indicates the strength of the sunscreen. But what does it actually mean? Let’s break it down.

SPF, which stands for sun protection factor, measures how well any given product protects your skin from the sun’s UV rays. Going into the sun without any protection at all can be considered as 0 SPF—the baseline against which all sunscreen products are measured. A sunscreen with a rating of SPF 15 means it takes 15 times the amount of sun exposure for your skin to burn than wearing no sunscreen at all.

It’s important to note that SPF does not measure the amount of time you can spend in the sun without getting burned. Rather, it measures the amount of solar exposure required to burn your skin. And these two things are subtly different. Consider the following example: one sunny morning you spend an hour outside at 9 a.m. and come inside without the slightest hint of a burn. The next day you spend one hour outside at 2 p.m. and get a slight sunburn. How is this possible? While the time spent in the sun was the same, the UV index was not. At 2 p.m. more of the sun’s ultraviolet rays were reaching the earth—and your skin.

As it turns out, our eyes aren’t too good at judging the UV index. Weather, altitude, and location can all affect UV index causing UV rays to be more or less intense, even if it looks cloudy. Many weather apps show the UV index throughout the day. So when in doubt, just double check. And always wear sunscreen when you’re outside.

How and When to Use Sunscreen

When it comes to sun protection, it’s crucial you use sunscreen correctly. This isn’t as simple as throwing some on in the morning and going about your day, but it’s not complicated either. Read on for a rundown of how to use sunscreen to get the best results.

  • How much sunscreen is enough? When applying (or reapplying) sunscreen, it’s important you use the correct amount. Dermatologists recommend applying about one shot glass—or 1.5 ounces—of sunscreen for your body and an additional teaspoon for your face. If this seems like a lot, that’s because it is. Most people under-apply sunscreen, ending up with uneven and partial coverage.
  • When should I reapply sunscreen? Regardless of your sunscreen’s SPF rating, you should reapply it at least every two hours. If you go for a swim, reapply when you get out of the water. And if you’re sweating heavily, be sure to reapply your sunscreen more frequently as your sweat may wash it off of your skin. Mineral sunscreens offer immediate protection, but it’s a good idea to wait 30 minutes after applying chemical sunscreens before heading back into the sun.
  • When should I wear sunscreen? If you’re going to be in the sun at all, it never hurts to wear sunscreen. Many skincare and cosmetics companies offer low SPF products (usually around 15 SPF) designed for daily use. And if you’re planning to be in the sun for a longer period of time (30 minutes and up) or plan to be out when the UV index is the highest (between 10 a.m. and 2 p.m.), it’s a good idea to apply sunscreen that’s at least 30 SPF. Oh…and don’t forget to reapply every two hours!

Sunscreen Myths and Misconceptions

In today’s world sunscreen is widely available and commonly used. But there are still a number of myths and misconceptions that need to be cleared up.

One of the most common sunscreen myths is that it actually causes sunburns and increases damage to your skin. There’s not any evidence to support this claim, but there is a possible explanation as to why people might think this way. And it all comes down to not using sunscreen correctly. Here’s the situation: when people wear sunscreen they sometimes feel it enables them to disregard other sun-exposure best practices. They stay out for hours without wearing protective clothing or reapplying sunscreen. As discussed, it’s absolutely vital to reapply sunscreen at least every two hours. So in this case, sunscreen is not causing sunburns but it is leading to riskier behavior.

This takes us right into another myth about sunscreen: anything over SPF 50 is actually bad for you. Again, there isn’t any evidence to support this conclusion. Researchers have observed the same pattern of riskier behavior from those who apply a higher SPF sunscreen. Even if you are wearing 75 SPF sunscreen, it needs to be reapplied every two hours or after swimming.

The Bottom Line

If you’re going to be basking in the sun, sunscreen is a must—it protects your skin, keeping it elastic and healthy for years to come. Apply more sunscreen than you think you need and reapply every two hours. If you find that sunscreen is causing your skin to break out, don’t drop it entirely. Instead try switching to a chemical sunscreen or finding one that’s formulated for acne and sensitive skin. With all of the products available, it’s worth finding the sunscreen that works best for you, your skin, and your lifestyle.