Sunscreen vs Sunblock: What’s The Difference?

We all know it’s important to wear sunscreen if we’re going to be out in the sun. No one likes the feeling of a sunburn and the chances of getting some kind of skin cancer in America are as high as one in five! You need to do what you can to minimize those chances and that means wearing sunscreen whenever you’re out, especially for things like fishing or spending the day on the beach. But wait, is it sunscreen you need to wear or sunblock? Is there even a difference? Turns out that yes, there is! Let’s take a look at what you need to know about sunscreen vs sunblock.

Sunscreen vs Sunblock

So you know you need to wear some kind of sunscreen and we’ve already offered some suggestions for different kinds of both chemical sunscreens and mineral sunscreens in other articles. You can even use powder sunscreen if you’re not a big fan of the feeling of creams and lotions. But understanding the difference between sunscreen and sunblock is also pretty important for maintaining sun health.

People use the two terms interchangeably all the time even though they may not mean to. It’s kind of like PVR or DVR. Is there a difference? Does it matter? For sunscreen and sunblock the answer is yes, there is a difference.

Sunscreens, in general, prevent the damage caused by UVA rays. Sunblock is designed to prevent UVB rays from damaging your skin. So what the heck are those?

UVA Rays vs UVB Rays

The ultraviolet radiation from our sun comes at us on different wavelengths. There’s even a UVC but our atmosphere protects us from that. UVA rays have a longer wavelength. Both kinds of radiation can lead to different forms of skin cancer.

UVA rays penetrate deeper into your skin and are also a major factor in the appearance of skin aging. Your skin will look dryer and older because of it, and you may develop more wrinkles or age spots.

The sun’s UVB rays, with their shorter wavelength, don’t go as deep into your skin. However, these are the rays that cause sunburns.

Both of these rays are radiation just like x-rays, gamma rays, and so on. When they contact your skin they can cause mutations in some of the cells. These mutations damage and destroy skin cells, this is actually a lot of what happens when you burn. And your body naturally tries to heal these damaged cells but some escape and continue to mutate and grow. That is what a cancer cell is, and they can spread if left untreated.

Is There a Different Sun Protection Factor for Sunscreen vs Sunblock?

SPF, or sun protection factor, is the number most people are concerned with when it comes to buying sunscreen and sunblock. There are two ways to understand what SPF means when you read the label on a bottle of sunscreen or sunblock.

Let’s use SPF 30, which is a common SPF. If you use it exactly as directed, and that’s an important thing to keep in mind because many people don’t always do this, then you can expect to stay in the sun 30 times longer than you could with no protection before you burn.

You can also understand SPF as a percentage. If you can stay in the sun 30 times longer, then an SPF 30 sunscreen lets in just a tiny bit over 3% of all the UVB rays you’re exposed to. Keep that in mind as well. SPF only refers to UVB radiation protection, not UVA.

A sunscreen or sunblock of SPF 50 lets you stay in 50 times longer meaning it only lets in 2% of all the UVB rays. That sounds like it’s barely a difference but in terms of sun exposure it’s actually very significant. Remember, at 3% it’s letting it 50% more UVB rays than 2%. Put that way it’s kind of dramatic.

Is SPF 15 Half as Good as SPF 30?

SPF 30 will prevent 97% of UV rays from hitting you. SPF 50 will prevent 98% of them. But SPF 15 only stops 93%. That still sounds good, right? Well, consider this. All of those SPF numbers were devised in lab tests. To determine how protected a person is, the tests involve using a 2mm thick layer of sunscreen or sunblock on the skin, which is what is the “recommended” usage. However, in practical tests it’s been shown most people never use anywhere near that much sunscreen. Most don’t even know that’s how thick it’s supposed to be. And, in fact, most of us are getting about 40% of the coverage we should be getting from sunscreen.

Based on those numbers, using an SPF 15 sunscreen means you’re practically using an SPF 6 and that is barely worth anything. Better than nothing? Sure. But still barely anything. If you’re going to spend the time and money on sunscreen, get something stronger. It makes more sense economically, and it will do the job of protecting you from harmful UV rays that much better.

How Do You Get Protected From UVA Rays?

If SPF doesn’t refer to UVA rays at all, then how do you get protected from them? The sunscreen industry has not done a good job of explaining this to people like us and what it all means. What you want to look for on any sunscreen or sunblock, because they will use both terms, is “broad spectrum.” If your sunscreen isn’t broad spectrum it means it is only blocking UVB rays. So a broad spectrum formula prevents both UVA and UVB from reaching your skin and that’s what you want.

How do Sunscreen and Sunblock Protect You?

Sunscreen usually, but not always, refers to chemical sunscreens. Sunblock usually, but not always, refers to mineral sunblocks. It relates to how each one prevents sun damage.

When you wear sunscreen, you put on a lotion that contains a variety of active chemical ingredients that absorb into your skin. Look on the label for compounds like oxybenzone or avobenzone as these are two of the most common chemical sunscreen ingredients.

When you are exposed to the sun, the UV rays penetrate your skin but the radiation is actually trapped by the molecules in the chemical sunscreen. The chemicals absorb the radiation and it undergoes a chemical reaction that converts it from UV radiation to heat. That heat is then released from your skin.

A sunblock is also called a physical sunscreen or mineral sunscreen. These use minerals like zinc oxide and titanium dioxide. You spread an actual layer of this on top of your skin and it acts like a shield that prevents the sun from reaching you at all. The radiation hits the physical barrier and  some of it bounces off. The rest is absorbed by the mineral itself through something called band-gap absorption. In that way a mineral sunblock can be much more effective than a chemical one because it prevents both UVA and UVB automatically. The physical layer of protection prevents any absorption. But with a chemical sunscreen both will penetrate the skin and if it is not broad spectrum, the UVA will not be affected.

Which is Better – Sunscreen or Sunblock?

Strictly by the numbers, sunblock is a better choice. Mineral sunblocks are broad spectrum because they physically do not allow either kind of UV radiation to pass through. That comes with a big warning, however. They must be used properly! That should go without saying but it happens very frequently that physical sunscreens are not used properly.

If you grew up on chemical sunscreens you’re used to rubbing the lotion in until it absorbs and disappears. This is how a chemical sunscreen works. You cannot do that with a mineral sunblock but the market seems to want that outcome anyway. If a sunblock is rubbed in so much that you can no longer see it, there’s a good chance it wasn’t rubbed in, it was rubbed off.

People don’t like mineral sunblock because they can see it on their skin. You look like you were painted white and for a lot of people, that’s a deal breaker. Many companies have tried to make invisible mineral sunblock, tinted mineral sunblock, and so on. But the fact is, if it’s a real sunblock and it does use zinc oxide or titanium dioxide then it absolutely must work if used correctly because it’s like using a tarp to stop the rain. There’s no way for the radiation to get around it. But if you poke holes in the coverage, even unintentionally, then there’s your problem.

None of this is to suggest sunscreen is bad. Especially broad spectrum sunscreens. These can be great. And as I often say, any sunscreen or sunblock is better than none. A good if scary statistic to keep in mind is that one in 5 Americans will get skin cancer in their lifetime. And just 5 sunburns in your lifetime can double your chances. Even one severe sunburn with blisters, just once in your life, can double the chance. So understanding the difference between sunscreen and sunblock, and how to use each, can literally save your life.

Are UV Rays the Same as the Sun’s Rays?

Like sunblock and sunscreen, these terms are often used interchangeably – sun rays and UV rays. Sun’s rays is a very vague and generic way to refer to the light from the sun. When you see someone talking about the sun’s harmful rays, that’s what they mean. The sun’s uv rays which can cause you to develop skin cancer. Just remember that it is bombarding you with two kinds of radiation and you need to be protected from both.

The Bottom Line

Sunscreen and sunblock mean the same thing to most people. As you can see, however, there are some significant differences. You’ll want to look for a kind that doesn’t cause skin irritation with sensitive skin and hopefully no allergic reactions. It’s best to get one that is water resistant and sweatproof as well.
The biggest takeaway you’ll want to remember is that any sunscreen or sunblock is better than none, so always try to have something on when you go out. Also that broad spectrum is the most important term you want to look for when shopping for either kind. If a sunscreen doesn’t say broad spectrum then it is only protecting you from UVB rays and that’s just not good enough.