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What is the Difference Between UVA and UVB?

What is the Difference Between UVA and UVB?

What You Need to Know About UV Rays and Sun Protection

Do you know the difference between UVA and UVB rays, what SPF actually measures, the importance of the UV Index or the meaning of broad spectrum? If so, you’re in the minority, with the latest National Sun Protection Survey revealing over 90% of Australians are missing the facts around UV radiation.  

It’s a worrying statistic, so to help shed a little light we’ve created this comprehensive guide to understanding UV rays. In addition to explaining the effects of UV radiation – both good and bad, we clear up the UVA vs UVB confusion and explain why daily sun protection is essential, all year ‘round.

What is UV Radiation?

Ultraviolet radiation, or UV radiation for short, refers to energy produced by the sun. There are three types of ultraviolet radiation (UVR): UVA, UVB and UVC. Each has a different wavelength and only UVA and UVB, which have relatively longer wavelengths, can reach the earth’s surface.

UV radiation is harmful to humans for several reasons, including its carcinogenic effects. A significant part of the threat lies in the fact that most UV rays cannot be detected by the senses. Invisible to the human eye, UV radiation – not to be confused with heat from the sun (Infrared radiation) – cannot be felt by the skin. Therefore, the only way you can ensure your exposed skin is protected is with daily sunscreen application.

Effects of UV Radiation

In addition to causing superficial sunburn and tanning, UV radiation damages the skin’s cellular DNA and can lead to melanoma and other skin cancers, as well as premature ageing of the skin. According to the Cancer Council, “Almost all skin cancers (approximately 99% of non-melanoma skin cancers and 95% of melanoma) are caused by too much UV radiation from the sun or [historically] other sources such as solaria (solariums, sunbeds, and sun lamps).”

Benefits of UV Rays

While the risks of UV radiation shouldn’t be underestimated, some exposure is, in fact, crucial for your wellbeing. Firstly, sunlight can positively impact our moods. So much so that health experts have identified a Seasonal Affective Disorder (SAD), where sufferers experience depression during winter’s reduced sunlight hours. 

The major health benefit of UVB radiation, however, lies in stimulating the skin’s production of Vitamin D. According to the World Health Organization, “Vitamin D has an important function in increasing calcium and phosphorus absorption from food and plays a crucial role in skeletal development, immune function and blood cell formation.” 

Thankfully, most of us will maintain healthy Vitamin D levels without having to risk the damaging effects of sun baking. “When the UV Index is 3 or above… most people maintain adequate vitamin D levels just by spending a few minutes outdoors on most days of the week,” says the Cancer Council. 

And if you’re deficient in Vitamin D? Dietary sources and supplements can bolster your levels as effectively as UV exposure, without putting you at risk of skin cancer.

UVA Vs UVB

UVA and UVB radiation are different types of ultraviolet radiation (energy from the sun), classified by wavelength. Ultraviolet A or UVA rays have the longest wavelength, while UVB rays are medium wavelength. Although shorter wavelength radiation is stronger and more damaging, it is also less effective at penetrating the skin. Therefore, both UVA and UVB are similarly harmful.  

But what’s the real difference between UVA and UVB? While somewhat simplistic, a quick tip to help you remember is this: UVA = Ageing rays and UVB = Burning rays.

Penetrating the deeper skin layers, UVA rays are considered THE major cause of premature ageing, contributing to loss of elasticity, wrinkles, pigmentation and roughness. In fact, up to 90% of visible skin ageing is caused by photoageing (sun-induced ageing) as opposed to chronological ageing.1

Long-wavelength UVA rays are by far the most prevalent, accounting for 95% of UV radiation that reaches the skin. Activating existing melanin, UVA rays are also those responsible for tanning in the short term.

Higher energy UVB rays, on the other hand, penetrate the surface layers of the skin and are the major contributor to sunburn. These rays also increase melanin production in the skin, for a delayed tanning effect.

While UVB exposure has long been identified as the main cause skin cancer, it is now acknowledged both UVA and UVB rays increase skin cancer risk.

UVA VS UVB Comparison List

UVA/UVB differences:

  • UVA accelerates skin Ageing whereas UVB causes sunburn & blistering
  • UVA has an immediate tanning effect, whereas UVB has a delayed tanning effect
  • UVA = ~95% of UV rays reaching Earth whereas UVB = ~5% of UV rays reaching earth
  • UVA penetrates glass whereas UVB does not penetrate glass

UVA/UVB similarities:

  • Long wavelength, lowest energy
  • Penetrates deeper skin layers
  • Invisible
  • Increases skin cancer risk
  • Sources: sun, solariums, sun beds
  • Penetrates clouds

Sunscreen in Winter & Ever-Present UVA

If you think sunscreen in winter is unnecessary, think again. The Cancer Council recommends sunscreen be worn any time the UV Index (which measures intensity of UV radiation) is 3 or above. In many parts of Australia, the UV Index reaches 3 or more for the majority of the year – including cooler days.

Additionally, while UVB radiation is less intense during winter, UVA rays remain present throughout the year at the same intensity. Able to penetrate through glass, they make daily broad-spectrum sun protection a necessity – even if you’re just running errands in the car or sitting by a window. [LS1] Yes, can we also add a paragraph here on UV index being over 3 almost all year round in Australia and the importance of creating a routine by putting sunscreen everyday on your face.

High SPF AND Broad-Spectrum = Total UV Protection

While choosing a sunscreen with a high-level SPF (50+ is the maximum SPF in Australia) deserves a pat on the back, for comprehensive protection it also needs to be ‘broad-spectrum’. This is because the Sun Protection Factor (SPF) of a sunscreen only measures its ability to filter out UVB rays and help prevent a sunburn. In the case of an SPF 50+, that means filtering out 98% of UVB radiation. However, UVA rays – which contribute to ageing and long-term damage – can still penetrate the skin, so make sure you choose a sunscreen that’s labelled as broad-spectrum.

Why Do I Burn so Easily?

Your genetics will impact how easily you burn, with fair people having less natural protection from melanin, and therefore an increased chance of getting sunburnt. Other reasons you might burn unexpectedly include not applying enough to all exposed areas of skin, not allowing enough time for it to absorb, and failing to reapply every two hours and after swimming or exercise. (Follow the link to learn how much sunscreen you should apply, and some other handy hacks.)  

In some cases, however, the redness you’re experiencing might not be sunburn. It could be a reaction to your sunscreen’s ingredients, or a condition known as polymorphic light eruption – caused by a reaction to the sun itself. You can learn more about these issues by reading our guide to sunscreen for sensitive skin.

The most important thing to remember? Even if you skip the burning phase and go straight to a tan, you are still putting your skin – and your health – at risk.

UV Protection – How to Protect Your Skin From UVA and UVB Rays

To recap, the best way to protect your skin from UVB and ever-present UVA rays is with daily application of a high-level, broad-spectrum sunscreen. Always read the label and use as directed, and make sure you choose a formula suited to your skin type.

In the La Roche-Posay Anthelios range of broad-spectrum sunscreens for sensitive skin, that means the non-greasy, easily absorbed Anthelios XL Ultra-Light SPF50+ fluid for normal to combination skin. Anthelios Ultra Facial Sunscreen SPF50+ is nourishing for dry, sensitive skin types, while Dry Touch SPF 50+ contains anti-sweat molecule Airlicium to help mattify oily and acne-prone skin as it protects. All Anthelios sunscreens are non-comedogenic, dermatologist-tested and available in tinted versions.

ALWAYS READ THE LABEL. FOLLOW THE DIRECTIONS FOR USE.

Apply 20 minutes before sun exposure. Sunscreen is only one part of sun protection so wear protective clothing and seek shade. Avoid prolonged sun exposure. Reapply every 2 hours and after swimming, towelling and perspiring in accordance with directions.

1.      Canadian Dermatology Association. (n.d.). Photoaging. Retrieved July 28, 2017

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