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What is the difference between UVA and UVB in sunscreen?

January 1 | 4 minute read

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Words by Emily Deacon

Originally published on | May 16

You might know your hyaluronic acid from your retinol, and your Drunk Elephant from your La Mer. But when it comes to the ultimate skincare hack (spoiler: it’s sun protection), do you know your UVAs from your UVBs? While ‘ultraviolet’ sounds like a particularly deep shade of purple, the reality is far less fun. But it’s important to brush up on the details, so that you can make sure your SPF is going the distance, especially since sun protection is just about the only step that is an absolute must in everyone’s skincare routine. Well, that, and taking your makeup off before bed.

You’ve no doubt heard the terms ‘UVA’ and ‘UVB’ thrown around, but perhaps aren’t entirely familiar with the difference between the two. That’s about to change, because we’re here to shed some light on the situation. And if you thought the UV index was basically another way to say ‘weather report’, think again. Here’s everything you need to get from (UV) A to B…

What is UVA?

The vast majority of the UV rays that reach your skin are UVA, making up a whopping 95 percent of the sun’s rays that touch the earth’s surface. Ultraviolet A are ‘long wave’ rays. They penetrate the skin much deeper than UVB rays, encouraging the formation of wrinkles, dark spots and other signs of sun exposure. And here’s the most insidious part: unlike UVB, you can’t feel the effect of UVA rays in the moment. So while they won’t cause a burn, you may be doing serious damage to your skin without even realising. UVA rays are also responsible for the tanning effect of sunlight. Think about the kind of gradual summer tan you might acquire incidentally, without sitting out to bake in the sun. That’s UVA.

These rays can travel through clouds and most types of glass, unless they’re specifically tinted with UVA-blocking material. So even if you’re in your car, or at your window-side desk on a gloomy day, you may still be at risk of exposure. If you’re guilty of skipping the SPF on overcast days or when you plan to be inside all day, consider this your wake-up call.

What is UVB?

UVB (Ultraviolet B) are ‘short wave’ rays which reach only as far as the epidermis. But don’t be fooled into thinking their surface-level makes them any less dangerous. With prolonged and unprotected exposure (which, on days with a high UV index can be a matter of minutes), UVB can cause those nasty sunburns we all know too well. UVB rays are also responsible for pigmentation and dark spots.

Although UVB does not penetrate as deeply as UVA, it’s a powerful force and it can wreak havoc on the top layers of your skin. UVB is intensified by higher altitudes, so if you’re hitting the slopes, you’ll want to slip, slop, slap before you do. And while UVA and UVB rays differ in how they affect the skin, they both have unwanted effects.

So what exactly is the UV index?

We’re so glad you asked! While we’ve all probably bandied the phrase about, do you actually know what the UV index is?

It’s a numerical range used to predict the UV exposure levels at midday, when the sun is generally highest in the sky. The UV index is specific to location, since weather and conditions can affect the UV exposure.

The UV index ranges from low grade (1-2) to extreme (11+). On low UV exposure days, it’s generally okay to be outdoors as long as you’re wearing SPF and taking regular precautions. On higher UV exposure days, it’s recommended to avoid being outside between the hours of 11am and 4pm and to wear SPF, a broad brimmed hat, sunglasses and seek out shade wherever possible if you have to be in the sun.

Don’t forget that reflective surfaces such as sand and snow can majorly increase the UV rays reaching your skin.

What is broad spectrum protection?

In the early days of SPF, sunscreen formulas only protected skin from the burn-causing UVB rays. However, once more was understood about UVA rays, sunscreen manufacturers began adding ingredients to protect from both UVB and UVA. The term ‘broad spectrum’ refers to sunscreens that filter both UVA and UVB rays. As we know, UVB is the principal cause of sunburn, but both UVA and UVB contribute to increased risk of sun damage. So, it’s important to have both bases covered by your choice of sunscreen.

Thankfully, there are now a plethora of incredible quality SPFs on the market, so there’s no need to sacrifice great skin for sun protection. Australia’s Therapeutic Goods Administration has strict guidelines in place regarding SPF products sold in Australia, so if you purchase a primary sunscreen product that advertises an SPF rating of 30 or above, you’ll be giving your skin excellent protection.

When choosing your broad-spectrum sunscreen, you’ll want to decide whether to go for a physical or mineral sunscreen, usually featuring zinc or titanium oxide, or a chemical sunscreen that uses UV filters like oxybenzone or homosalate. Chemical sunscreens tend to have a thinner, more spreadable feel, and are less likely to leave a white cast. On the other hand, mineral sunscreens are a great option for those with sensitive or blemish-prone skin, though they can have a thicker formulation and leave a white cast. A little sampling will help you decide which is right for you.

Regardless of the SPF you’re reaching for this summer (and all year round, for that matter) just remember: always avoid prolonged sun exposure and wear protective clothing, a (chic) pair of sunnies and a hat.

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Skin careSunscreen

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