How Does Sunscreen Work?

Don’t you hate that feeling when you go outside for a nice day at the beach, and you come back with skin that looks (and feels!) like it was baking in the oven all day? Sunscreen was invented for the sole purpose of preventing this tragedy from happening to your precious skin. If you find yourself asking the question, “How does sunscreen work?”, the answer lies in understanding why you need it in the first place.

What causes sunburn?

Contrary to popular opinion, it isn’t direct sunlight that makes your skin look like a Thanksgiving dinner after a hot day out. There are invisible rays in sunlight called ultraviolet rays (UV rays). When your skin is exposed to this radiation for a long period of time, it reacts by swelling, turning red, and causing pain.

When UV radiation hits your skin, it causes damage to the skin cells and the DNA in them. This leads to substances being produced in your skin that force the tiny blood vessels right under your skin to expand. The result? The red patches that you know are the signs of sunburn. The damage to your skin cells can cause them to wither up and die too, which is why your skin sometimes peels when the sunburn is extra bad.

Types of UV radiation

There is more than one kind of UV radiation, which is why the question “how does sunscreen work?” needs to be broken down like this. Remembering the types is as easy as A B C, mainly because they literally are called UVA, UVB and UVC.

UVA has the longest wavelength, which is a crest-to-crest measure of the length of each wave that makes up the radiation. Because of this long wavelength, UVA can move through glass, the earth’s ozone layer, and deep into your skin tissue. This leads to premature aging of your skin! It can also lead to skin cancers like melanoma. The problem with the A type is that you won’t notice the damage it’s doing immediately. Instead, after years of insufficient sun protection you’ll notice that your skin is aging and your doctor is concerned about dark spots on your skin.

UVB, on the other hand, has a shorter wavelength. The ozone layer blocks out some of it and it can’t reach you through windows. It penetrates into the layer of cells right under your skin and irritates them, which causes sunburns and over time can also lead to skin cancer. Most sunscreens target UVB because of its more noticeable effects, although certain types of sunscreen protect you from both UVA and UVB radiation (they are called broad spectrum).

UVC isn’t an issue usually because of its super-short wavelength. This means that the ozone layer blocks it out completely. This type of radiation is an issue in tanning beds, and in parts of the world where the ozone layer has depleted enough to let the radiation through.

How does sunscreen protect your skin?

So, how does sunscreen work to fight sunburns? Well, it uses a combination of natural and/or artificial ingredients in a potent cocktail that does one of three things:

• reflect the UV radiation
• disperse the UV radiation
• absorb the UV radiation so it is wasted as heat

‘Physical’ sunscreens use natural ingredients like titanium dioxide and/or zinc oxide to form a literal ‘screen’ on your skin that reflects and scatters UV rays before they reach your skin. ‘Chemical’ sunscreens use various chemicals to absorb certain wavelengths of UV radiation so they can be converted into heat.

Hybrid sunscreens use combinations of both physical and chemical ingredients to protect skin against UV radiation.

The type of sunscreen you use has nothing to do with its Sun Protection Factor (SPF). This confusing measurement indicates (rather poorly) how much UVB radiation is blocked by a sunscreen. Experts recommended SPF 30 and up sunscreens, though you should know that after SPF 30 you get minimal protection for increases in SPF.

Common sunscreen ingredients and what they do

As mentioned above there are two major types of UV filtering ingredients found in sunscreen: chemical and physical (also called ‘mineral’). Each has its own function in protecting your skin from the sun’s rays.

The most common chemical active ingredients include:

• Avobenzone: this compound protects your skin against UVA radiation. It doesn’t pass through your skin into your blood easily, which was a common issue when sunscreen was first invented using different chemicals.
• Octinoxate and Homosalate: these are found naturally in breast milk. They are useful in protecting against skin irritation by UV-B light. Concerns have been raised that they disrupt hormone production in your body and increase toxicity.
• Octisalate: Most sunscreen containing avobenzone has this as a stabilizing agent. It is very soothing and doesn’t cause allergic reactions in humans.

The most common physical active ingredients are:

• Zinc oxide: while you can find zinc oxide naturally, it is easier to just manufacture it. It is another UV reflector and disperser. You usually find zinc oxide in broad spectrum sunscreen because it is the best active ingredient as it can reflect all of the UV spectrum from the longest wavelength UVA through to the shortest UVB.
• Titanium dioxide: this is a mineral that is found naturally in the world. You probably know it as the ingredient that makes sunscreen look white. It is used in other skincare products as well, mainly because it is highly effective at reflecting UV light off your skin. When exposed to UV for long periods of time, titanium dioxide remains chemically stable, which reduces your risk of allergies and skin irritation.

Vitamin D, sunscreen, and you

UVB light has a useful function in your body – it aids in the production of Vitamin D in your skin cells. Because sunscreen blocks out UVB, you might think that your Vitamin D production is reduced by dangerous amounts. The truth is that no one applies sunscreen well enough to block out all UVB light. In the small doses that remain, the light rays are neither harmful nor toxic to your cells and they all your Vitamin D to continue as normal.

Now that you know how sunscreen works to protect your skin against cancer, irritation, sunburns, and aging, check out the SimplySunSafe buyer’s guides that will help you choose a sunscreen to suit just about every need.