UVA and UVB? – The Sunblock 101

We all know what the sun is, and why we should protect our skin from direct sunlight, but do you actually know what sunblock does and how you should apply it? I wanted to come back with another 101 lesson, because not only is it Summer over in the states and in Asia, but it’s drawing closer to the hotter days here in Perth too. Sun protection is a must and so, here I am with my 101 lesson on how to effectively protect your skin.

Today, I’ll be covering:

  1. The difference between UVA and UVB
  2. SPF and PA protection
  3. Physical and Chemical sunblock
  4. Common Q&A’s with sunblock
  5. Correct application of sunblock

UV rays are split into 3 different ray forms. UVA, UVB and UVC. Luckily for us, UVC is readily absorbed by the dead layers of our skin and does little to no harm. What about UVA and UVB then?

UVA are long rays of radiation and are the most damaging to our underlying skin cells. They are the main cause for wrinkling and premature aging. UVA rays also have a huge impact on our pores as well, causing them to enlarge over time which causes larger, more pronounced pores and skin sagging. Did you know that up to 90% of our wrinkles are caused by UVA rays? It takes roughly 20 to 30 years before you’re able to see the true effects of UVA damage to the skin, but with regular exposure to unprtected skin, the damage builds up and soon enough, you’ll be looking like a prune. UVA rays are so potent they can penetrate through almost anything. Sitting by a window indoors with sunlight hitting your face? You’re still exposed to UVA rays honey. Not even the window can help you in your need of time.

UVB rays are shorter in wavelength and aren’t as potent as UVA rays are. They however, are the cause for skin tanning and sunburn. Of course, with that, it can cause skin cancer too. UVB is more forgiving though towards those with a darker skin complexion. Rule of thumb is, the more fairer your skin tone, the more easier it is to see, AND experience the effects of UVB damage. 

How can you determine the protection value of your sunblock? On your sunblock bottles, you’ll see SPF written by it with a number value. SPF indicates protection against UVB rays. Some say that more UVB rays are filtered based on how high the SPF value is. This is necessarily not the case. SPF indicates how long your skin is protected against UVB, and not the percentage of rays filtered out. SPF1 can protect your skin for 10 minutes before you have to reapply. Honestly though, who has the time to reapply sunblock every 10 minutes? Not me, hence why the recommended SPF value you should be using is set at 15, which is 2hrs and 30mins worth of protection. SPF30, which is the normal value for sunblocks these days is set for 5hrs of protection.

So, does applying 2 products with SPF30 value, give you the protection of an SPF60 product? NO! This is a huge myth that I wanted to crack today. SPF value does not add on top of each other, so for those people who think you get a longer duration for your sunblocks by applying in layers, then think again. How about applying SPF with different values on top of each other? The SPF product that has the higher value will be the amount of protection you get. For example, a product with SPF50 and a product with SPF30 applied over, will give you an SPF protection of 50,not 80.

PA indicates the protection of UVA rays. Your sunblock will show you PA with up to three + signs which indicates the protection value. One + sign is the lowest protection and four + signs is currently the highest protection available in the market. Unluckily for those who use Western branded sunblocks, the PA value isn’t shown on the bottle. You guys will see broad spectrum printed on the packaging but that’s about it. Broad spectrum indicates you get protection against BOTH UVA and UVB but you don’t get an actual value for UVA protection. Who knows exactly how much your sunblock will protect you for.

Just like the SPF value, PA value does not stack on top of each other. So, two uses of PA++ sunblock will not give you PA++++ protection. You will still get only PA++ protection. Of course, this applies for different value sunblocks as well. Using PA+++ with a sunblock with PA+ protection will ultimately give you PA+++ protection. 

So, who should be applying sunblock? If you’re over 6 months old and exposed to any form of sunlight then you should be applying sunblock. A baby’s skin is extremely delicate, so it’s noted at the age of 6 months, it’s best to keep the baby’s skin as healthy as possible by protecting it with a UV shield to avoid skin damage. Saying that though, baby’s skin is also very thin and therefore, more sensitive to adult skin, so what kind of sunblock suits them best? 

There are two different types of sunblock in the market. Physical and chemical which work differently to each other. Physical sunblock creates a shield on the skin that reflects the sun rays AWAY from the skin as if it’s bouncing off. You might have heard people refer to this type of sunblock as bounce cream, because of the theory behind how physical blocks work. Chemical sunblock actually ABSORB the sun rays into the skin and create a chemical reaction to turn the radiation into heat in order to block the damage. There are 6 key points to address when choosing which sunblock is best for you.

  • Turbidity

Physical sunblock have a huge amount of turbidity based on the ingredients. You’ll notice when you apply physical blocks, it leaves a greyish-white cast on the skin, which to some, may not be ideal for them. The turbidity of physical sunblock however, can keep skin fairer over time, and is ideal for those who are looking to protect their skin tone.

Chemical sunblock has no turbidity and leaves no cast whatsoever on the skin. Most people opt for chemical sunblock when applying makeup, because of it’s natural finish.

  • Instant Effect

Physical sunblock instantly creates a shield for the skin to protect against UV damage by reflecting sun rays away. That means, you can be exposed to the sun as soon as you apply a physical sunblock. For convenience, physical sunblock is more quicker to use on busy or rushed days.

Chemical sunblock works differently by absorbing sun rays, so the shield effect doesn’t apply for this type of sunblock. You may have heard people tell you to wait 30 minutes before exposure to the sun after using sunblock. This is the type of sunblock that this applies to. This is due to the fact that you need time for your skin to fully absorb the sunblock for the effects of protection to work. Most people only recommend chemical sunblock to those who have extra time to sit around and wait in the morning for lack of convenience.

  • Lasting Ability 

Physical sunblock lasts longer than chemical because of it’s shield effect. Even when your skin absorbs the sunblock, you still have that shield protecting your skin, so for those working indoors and are using physical block, then rest assured your skin will still be fairly protected. Physical sunblocks tend to be waterproof too, meaning they have an astounding lasting ability and protect your skin from weather and sweat.

Chemical sunblock fully absorbs into the skin, so your protection time is limited to roughly 3hrs since chemical doesn’t have the shield effect. You have to reapply chemical sunblock every 3 hours to keep your skin protected, even indoors, and most especially if your face gets wet.

  • Blending Ability

Physical sunblocks run very thick because of it’s fat forming elements in the ingredients. They use mineral dust types of ingredients to protect the skin, which contributes to it’s viscosity and finish. Since mineral dust is powdery, it makes the formula more dry and not the best to fit the skin texture as you’re required to work the product into the skin with a lot more effort than normal for absorption. Physical sunblock may also clog pores because of it’s fatty formula.

Chemical sunblock has a more creamy and moist texture which readily absorbs into the skin, just like a moisturizing lotion. Most chemical sunblocks have a runny viscosity to them, some even resembling the viscosity of hydrating toners. These however, tend to feel more oilier and more wet, than physical sunblocks.

  • Irritation

Physical sunblock doesn’t use chemical reactions to protect the skin, rather they use a shield effect to bounce radiation away from the skin. Physical sunblocks are recommended for those with sensitive skin types, and babies who’s skin is most delicate.

Chemical sunblock works by absorbing sun rays into the skin and converting the rays into heat to be absorbed. This chemical reaction can irritate those with sensitive skins and can cause your baby to have skin allergies when used on their delicate skin. I must say that Asian branded (not too sure of the Western brands) sunblocks that are 100% chemical, have all been thoroughly tested to be hypoallergenic and nobody can really say that one sunblock is better than the other based on this alone. However, rule of thumb is that the more sensitive your skin is, the less you should use chemical sunblock to reduce the likelyhood of skin irritation.

  • Ingredients

Physical sunblock contains only two main ingredients.

Titanium dioxide, Zinc (II) Oxide

Any sunblock that has either or both of these ingredients fall under the physical sunblock category. Rule of thumb, if your sunblock doesn’t contain these two ingredients then assume the sunblock is a chemical type!

Chemical sunblock contains the following ingredients. 

Avobenzone, Oxybenzone, Octylcrylene, Octinoxate, Octisalate, Homosalate, Helioplex, 4-MBC, Mexoryl SX and XL, Tinosorb S and M, Uvinal T150, Uvinal A Plus. 

Any sunblock that contains these ingredients offers you chemical protection against UV rays. You’re more likely to find a sunblock that has BOTH an ingredient of a physical block with an ingredient from a chemical together, than you would a 100% chemical sunblock.

Of course, by now you should know what sunblock is and how each one works. But what about the most important of all? How to apply and use sunblock effectively? And, what about questions that have now arose from all these facts? I’ll answer the 3 most commonly asked questions I could find on the internet.

Can I apply a makeup product with SPF value in replacement of sunblock?

No you can not. Some may argue with this, but I feel that makeup that offers SPF and PA protection will not guarantee you any sort of protection whatsoever, unless you use the suggested amount of sunblock for your makeup, which is two knuckles worth or the size of an AU 10¢ piece (a quarter for US currency.) Did you know that not applying enough sunblock to your skin reduces protection rates by 75%? Let me ask though, are you willing to apply THAT MUCH base on your face and risk looking like the monster from The Grudge? I strongly suggest you apply sunblock before makeup to guarantee some form of protection for your skin. As long as you use your sunblock and SPF makeup, making up the quantity of the suggested sunblock amount is ok. 

For example, let’s say the suggested amount of sunblock is 50mL to be used everyday. If your makeup offers no protection whatsoever, you MUST use 50mL of sunblock before applying makeup. If your makeup offers you sun protection, then using 30mL of sunblock and 20mL of makeup is ok, since you’re still reaching the required 50mL necessary. You understand? I still stand by my word though, and think you should apply sunblock correctly first, before applying makeup, SPF protection offered or not. It’s definitely better to apply extra sunblock than to apply not enough.

I applied just sunblock onto my skin. Can I wash my face with only foam cleanser?

No you can not. Treat sunblock as if it were a makeup product when you’re washing your face. Would you wash your makeup off with just a foam cleanser and risk skin damage and irritation? I hope not! Sunblock, particularly physical sunblock, can clog pores and are made up of fat forming components, so a product that breaks down oil into particles is necessary in your cleansing routine when dealing with sunblock. You can actually read how to cleanse your skin correctly clicking here. If your sunblock is waterproof, then most definitely cleanse your skin with an oil type cleanser before going ahead and using your foam. Makes sense, cause obviously the sunblock is waterproof, and you’d be silly to use just water to clean the sunblock off with a cleanser. If your sunblock isn’t waterproof, then though I strongly believe an oil cleanser is necessary, a micellar water before your face wash can ultimately be enough to rid your skin from the sunblock.

Is it true that the higher the protection, the more likely it can irritate my skin? 

Unfortunately, yes it does. The higher the value of the protection, the more stronger it is to keep skin free from damage, thus, more chance to irritations and troubles. If your skin is easy to react with sunblock, then I recommend using a lower SPF and lower PA rating sunblock and regularly apply throughout the day. It’s better to apply a lower protection sunblock every 3hrs than to apply a higher protection sunblock once in the morning.


Every single day, I treat sunblock as a step of my skincare routine. Whenever I do my skincare, without fail, I always use sunblock depending on what I use. My general rule of thumb is the more hydrating my skincare is, or the more layers I apply, the less thick my sunblock will be. The less hydrating my skincare is, or the less layers I apply, the thicker my sunblock is. This is because physical sunblocks aren’t readily blendable, and apply thickly, so when used on a sticky, hydrated face, the sunblock doesn’t blend into my skin. Vice versa, when my skin isn’t too moist, thicker sunblocks like physical type soak extremely well and provide a more satin finish, yet not drying to keep my skin in check.

With chemical sunblock, when applied on top of a thick skincare routine, it adds just the right amount of oiliness to my skincare to really balance out the moisture, and doesn’t feel too heavy on the skin. It also soaks in almost instantaneously which works well for a complex routine. With a more limited skincare routine however, chemical sunblocks tend to feel extremely oily and a tad uncomfortable, even if it’s designed to give ampoule hydration. I also tend to do smaller skincare steps when I’m in a rush, so I usually don’t have the time to wait 30 minutes before leaving the house. This is just my personal way of using sunblock, and what may work for me, will necessarily not always work for you. The best way to see which sunblock works for your face, is to apply it directly to your skin. Not your hands, but your face. If you happen to receive any samples, they’re a great way to try before you buy, or if not, most Asian cosmetics stores will have testers of sunblock for you to give a shot as well.

If you liked this lengthy post about sunblock or found it helpful in any way, then don’t forget to share with your friends and family, subscribe to my blog and leave comments down below on what you’d like to read next. As per usual, you can find all my SNS sites down below.

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