UVA vs UVB

What is UV radiation?

The sun emits energy that produces heat and light. This radiation has a range of wavelengths, which is known as the solar spectrum. Some of the radiation is filtered by the atmosphere and never reaches Earth. Some is partially filtered but still has an impact on our skin. This includes UV rays, visible light and infrared[i].

1. Ultraviolet (UVA & UVB)
   1. Cold and invisible to the human eye 
   2. Approx 2-5% of solar radiation¹
2. Visible light (VIS)
   1. Including blue /HEV light
   2. Approx 47% of solar radiation¹
3. Infrared (IR)
   1. Invisible but can be felt because of the heat produced 
   2. Approx 51% of solar radiation¹

UV radiation is divided into:

• Short and long UVA comprising 95% of UV¹, which can pass through windows and 
• clouds
• UVB with a shorter wavelength than UVA, representing 5% of UV¹, which emits a lot of energy but doesn’t penetrate as deeply
• UVC with a short wavelength – it is extremely dangerous but doesn’t reach the Earth’s surface as it is filtered by ozone in the atmosphere 

What is the difference between UVA and UVB?

UVA and UVB rays don't damage the skin in the same way

Both kinds of UV radiation are harmful to the skin, but they don't have the same impact. 

• UVA rays penetrate deep into the skin and have a long-term impact because of their oxidative effect[i]. By generating free radicals[ii], they trigger accelerated photoaging[iii] and damage the body’s collagen and elastin production, leading to the appearance of wrinkles and pigmentation marks. They may also contribute to the development of skin cancer over time⁴.

• UVB rays provoke sunburn in the short term⁴ and play a direct role in the development of skin cancer and cataracts in the longer term[iv]. As a high energy source, UVB rays cause direct DNA damage^4,5 leading to genetic alterations that can contribute to different forms of skin cancer such as melanoma.

Different UV wavelengths 

UVA rays have a wavelength between 315-400 nm (nm = nanometre). Short UVA rays between 315-340 nm mostly reach the epidermis, while long UVA rays between 340-400 nm penetrate deep into the dermis.

• Impacts on skin: aging including wrinkles and sagging, pigmentation marks, oxidative stress, inflammation and, in the longer term, a greater risk of skin cancer

UVB rays have a wavelength between 280 and 315 nm. They reach the epidermis and superficial skin layers. They can also affect the eye lens. 

• Impacts on skin: sunburn, genetic alternations responsible for some skin cancers, and cataracts 

A combination of UVA and UVB rays amplifies the damaged caused, particularly to DNA⁴, increasing the risk of developing skin cancer.

UVA rays are far more prevalent than UVB rays

UVA rays represent around 95 % of the UV radiation that reach the Earth’s surface, UVB makes up the remaining 5%. Sun protection based on the SPF system was initially developed to protect against sunburn – so therefore UVB radiation. Today, we have a much better understanding of the impact of solar radiation on skin, and modern sunscreens offer broad-spectrum protection. They are designed to protect against UVB, UVA, visible light and infrared. 

The aim? Provide comprehensive protection against the negative impacts of the solar radiation including sunburn, but also premature skin aging and longer-term consequences for the skin and health. 

UVB rays have more energy than UVA rays 

With a shorter wavelength than UVA rays, UVB radiation penetrates the skin less deeply. However, the rays have a lot of energy meaning that, in high quantities, they are dangerous for the skin. UVB radiation can damage the body’s genome as it is absorbed directly by DNA in skin cells, provoking reactions that can alter its structure[i] and increases the risk of cancer in the long term. 

Why do we also need protection against infrared and visible light?

The effects of UVA and UVB are now well known, but other types of radiation can also damage the skin and present health risks. Recent research has focused on the negative impacts of visible light and infrared radiation.

• Visible light (400-700 nm) represents around 50%[i] of oxidative stress triggered by solar radiation. In particular, blue light or high-energy visible light (400-450 nm)[ii] generates free radicals[iii] in the skin⁷ and can lead hyperpigmentation like melasma⁴. Exposure to visible light outside is more intense than indoors and therefore more harmful to the skin[iv].

• Infrared (760 nm-1 mm) creates a warm feeling and increases the effects of UV rays by contributing to the production of free radicals, which accelerate photoaging.^9,[v]

Effective sun protection therefore needs to protect skin against visible light and infrared, as well as UVA and UVB rays.

¹Passeron, T., Krutmann, J., Andersen, M. L., Katta, R., & Zouboulis, C. C. (2020). Clinical and biological impact of the exposome on the skin. Journal of the European Academy of Dermatology and Venereology, 34(S4), 4–25. https://doi.org/10.1111/jdv.16614

2 Deparois, M. (2014). LES EFFETS DES RAYONNEMENTS ULTRAVIOLETS SUR LA PEAU : LES CONSEILS DU PHARMACIEN D'OFFICINE

3 Jeanmougin. (2000). Peau et soleil. Encyclopédie Médico-Chirurgicale, 468874, 8.

4 Passeron, T., Krutmann, J., Andersen, M. L., Katta, R., & Zouboulis, C. C. (2020). Clinical and biological impact of the exposome on the skin. Journal of the European Academy of Dermatology and Venereology, 34(S4), 4–25. https://doi.org/10.1111/jdv.16614

5 Guan, L. L., Lim, H. W., & Mohammad, T. F. (2021). Sunscreens and Photoaging: A Review of Current Literature. In American Journal of Clinical Dermatology (Vol. 22, Issue 6, pp. 819–828). Adis. https://doi.org/10.1007/s40257-021-00632-5

6 Douki, T., Leccia, MT., Béani, JC., Mouret, S., Cadet, J., Favier, A. (2007) Harmful effects of solar UVA radiation: new indices in DNA Med Sci (Paris) 2007 ; 23 : 124–126

7 Zastrow, L., Groth, N., Klein, F., Kockott, D., Lademann, J., & Ferrero, L. (2009). UV, sichtbares Licht, Infrarot : Welche Wellenlängen produzieren oxidativen Stress in menschlicher Haut? Hautarzt, 60(4), 310–317. https://doi.org/10.1007/S00105-008-1628-6/METRICS

8 Liebel. (2012). Irradiation of skin with visible light induces reactive oxygen species and ...: EBSCOhost. Journal of Investigative Dermatology.

9 Mann, T., Eggers, K., Rippke, F., Tesch, M., Buerger, A., Darvin, M. E., Schanzer, S., Meinke, M. C., Lademann, J., & Kolbe, L. (2020). High-energy visible light at ambient doses and intensities induces oxidative stress of skin—Protective effects of the antioxidant and Nrf2 inducer Licochalcone A in vitro and in vivo. Photodermatology Photoimmunology and Photomedicine, 36(2), 135–144. https://doi.org/10.1111/phpp.12523

¹⁰ Farris, P. K., & Valacchi, G. (2022). Ultraviolet Light Protection: Is It Really Enough? In Antioxidants (Vol. 11, Issue 8). MDPI. https://doi.org/10.3390/antiox11081484

¹¹ Chen, J., Liu, Y., Zhao, Z., & Qiu, J. (2021). Oxidative stress in the skin: Impact and related protection. In International Journal of Cosmetic Science (Vol. 43, Issue 5, pp. 495–509). John Wiley and Sons Inc. https://doi.org/10.1111/ics.12728

¹²Damevska, K., Nikolovska, S., Kazandjieva, J., Trifunova, B. K., & Bocheva, G. (2019). Skin and pollution. In Advances in Integrative Dermatology (pp. 379–392). wiley. https://doi.org/10.1002/9781119476009.ch24

¹³Dreno, & Araviiskaia. (2019). The impact of airborn pollution on skin. JEADV, 33, 1496–1505. https://doi.org/10.1111/jdv.15583