Difference between UVA and UVB: Effects, Protection, Myths

Whether at the beach, on the balcony or at a desk by the window: UV radiation hits your skin every day. The crucial difference between UVA and UVB determines how quickly you tan, whether you get sunburn and how high your long-term risk of skin damage is. Here you’ll find a clear explanation, a compact comparison table and concrete protection tips so you can handle UVA and UVB safely. Why consistent UV protection is so important in your routine: Sunscreen: the most important step in your skincare routine.

UV spectrum in brief

Ultraviolet radiation is invisible light with a shorter wavelength than visible light. It is divided into three ranges: UVC (100–280 nm, filtered by the atmosphere), UVB (about 280–320 nm) and UVA (320–400 nm). UVB has more energy per photon and quickly causes sunburn. UVA reaches the Earth in a larger proportion, penetrates deeper into the skin and drives long-term damage such as photoaging. For you, UVA and UVB are most relevant because both influence tanning, sunburn, skin cancer risk and vitamin D production.

UVA rays: deeper impact, long-term damage

UVA accounts for around 95 percent of the UV radiation reaching the Earth and is present year-round and almost all day at relatively constant levels. With wavelengths of 320–400 nm, UVA penetrates into the dermis. We distinguish UVA2 (320–340 nm) and UVA1 (340–400 nm). These rays rarely cause acute sunburn but damage collagen structures, promote reactive oxygen species and thereby cause indirect DNA damage. The consequences show as photoaging: wrinkles, loss of elasticity, pigmentation changes and an increased risk for certain skin cancers.

Important for everyday life: UVA passes through ordinary window glass. That means even in the office or in the car without appropriate glass or film protection, you are exposed to UVA. UVA also causes a quick, often short-lived immediate tan by oxidizing existing melanin. Don’t rely on overcast skies or staying indoors—use consistent broad-spectrum protection with strong UVA coverage.

UVB rays: acute reactions and vitamin D

With 280–320 nm, UVB carries more energy per photon, reaches mainly the epidermis and is the primary trigger of sunburn. Its intensity varies greatly by season, time of day, latitude and altitude. UVB is largely blocked by window glass, but outdoors it’s especially strong around midday and in the summer months.

UVB stimulates melanin production and leads to a delayed, longer-lasting tan. At the same time, UVB causes direct DNA damage that raises skin cancer risk if protection is insufficient. On the plus side, UVB is relevant for your body’s vitamin D synthesis. That’s not a free pass for unprotected sun: short, controlled exposure during moderate UV index times is usually enough, while sunburn should always be avoided.

Difference between UVA and UVB at a glance

Which is more dangerous: UVA or UVB?

Both are risky—just in different ways. UVB shows danger immediately with redness and sunburn and causes direct DNA damage. UVA is quieter but persistent: it accelerates skin aging, suppresses parts of the immune system and contributes to skin cancer risk through indirect DNA damage. Because UVA acts year-round and also behind glass, it’s often underestimated. For you it’s not either/or, but effective protection against both spectrums.

Factors that influence UV intensity

How strongly UVA and UVB reach you depends on several factors. Around midday and in summer, UVB is especially intense. At higher altitude, UV radiation increases noticeably per 1000 meters. Bright surfaces reflect rays: snow a lot, sand and water considerably. Clouds only partially reduce UV—diffuse radiation remains relevant. Your location and season matter, too. Use your region’s UV index as guidance. The higher the value, the more consistently you should apply protection measures.

Protect properly: how to block UVA and UVB

Choose broad-spectrum protection that covers UVA and UVB. SPF primarily refers to UVB and sunburn protection, while UVA performance is often indicated with PPD or PA. Look for PA+++ or PA++++ and modern filters that deliver high UVA coverage. Learn how to pick the right Korean sunscreen for your skin in our guide. Unsure about chemical vs. mineral? This article explains the differences.

• Amount and application: For the face, about two finger lengths of sunscreen; for the body, around 2 mg per cm². Apply 15–30 minutes before sun exposure, reapply every 2 hours and after sweating, swimming or toweling off. Tip: The 3‑finger rule helps with the right amount.
• Timing and shade: Avoid strong midday sun, seek shade and check the UV index.
• Clothing: Densely woven textiles or certified UV-protective clothing, wide-brimmed hats and UV400 sunglasses.
• Kids and sensitive skin: Prioritize high UVA/UVB coverage, gentle formulas and consistent reapplication.
• Indoors and in the car: UVA passes through glass. Use suitable protection at the windowed office or on long drives.

Find more options in our Sun Care (SPF) category.

Suitable broad-spectrum sunscreens at NoticeMe:

• Isehan - Kiss Me Mommy UV Mild Gel SPF33 PA+++ – gentle, ideal for sensitive skin and babies, with protection against UVA and UVB.
• Kose - Suncut Light Up UV Essence SPF50 PA++++ – very high protection, water- and sweat-resistant, long-lasting UVA/UVB protection.
• SKIN1004 – Madagascar Centella Tone-Up Sunscreen SPF50+ PA++++ – broad-spectrum protection with Centella, ideal for daily use.

Additionally, find protective care in our Protect collection: protection & care.

Frequently asked questions

Which is better, UVA or UVB?

Neither is better or worse—they’re different. UVA mainly causes long-term damage like skin aging, UVB triggers sunburn. You need protection against both.

Which tans more, UVA or UVB?

UVA leads to a quick immediate tan that fades fast. UVB triggers melanin production and results in a slower, longer-lasting tan. Protection is important in both cases.

Which causes skin cancer, UVA or UVB?

Both contribute to skin cancer risk. UVB causes direct DNA damage, UVA causes indirect DNA damage and immunosuppression. Combined, consistent protection lowers your risk.

Why not SPF 50?

SPF 50 makes sense, especially with high UV intensity or fair/sensitive skin. The key is using enough product and reapplying regularly. Also look for strong UVA coverage, e.g., PA++++.

Do UVA rays penetrate windows?

Yes, conventional window glass lets UVA through to a large extent. UVB is blocked more strongly. That’s why broad-spectrum sunscreen is worthwhile even by the window.

How much sunscreen do I need for my face?

As a rule of thumb, use two finger lengths of product for face and neck. This amount helps achieve the labeled protection.

With the knowledge of the difference between UVA and UVB, you can make your everyday life sun-safe. Check the UV index, choose broad-spectrum protection and stick to the right amount and reapplication. Your skin will thank you in the long run.