UVA vs UVB: what matters for your skin

UVA and UVB rays damage your skin in different ways, but both require daily protection. UVA (315–400 nm) penetrates deep into the dermis and drives premature ageing, while UVB (280–315 nm) burns the surface and causes most direct DNA damage. The World Health Organization and the NHS both recommend broad-spectrum SPF 30 or higher sunscreen every single day, regardless of the season.

Three things you can do right now:

Choose broad-spectrum SPF 30+ so you’re covered against both ray types, not just one.
Cover up and wear sunglasses to block what sunscreen alone can’t reach, especially around your eyes.
Reapply every two hours and seek shade between late morning and mid-afternoon, when UVB peaks.

Key Takeaways

UVA ages skin through deep, cumulative exposure while UVB burns it directly, so broad-spectrum SPF 30+ applied daily is the single most effective everyday defence against both.

Point	Details
UVA dominates exposure	UVA makes up around 95% of surface UV and penetrates deep into the dermis, driving premature ageing.
UVB causes burning	UVB is only about 5% of surface UV but carries higher energy, causing sunburn and direct DNA damage.
UV strength varies	Time of day, season, altitude, and reflective surfaces like water and snow all raise exposure levels.
Broad-spectrum is essential	Only a broad-spectrum label confirms protection against both UVA and UVB, not just one.
Choose non-toxic daily protection	Fierce Nature’s Sun Balm SPF 50 offers broad-spectrum, tallow-based protection without synthetic filters.

Authoritative sources behind this article

NHS — daily sun safety recommendations and UV Index guidance.
CDC — breakdown of UVA, UVB, and UVC composition at ground level.
Cancer Research UK — evidence on tanning beds and melanoma risk.

This article is general information, not a substitute for advice from a qualified doctor. Consult a qualified healthcare professional about your own circumstances before acting on anything here.

What is ultraviolet radiation and its three bands?
UVA rays: properties, penetration and typical effects
UVB rays: properties, surface effects and immediate dangers
When and where is UV strongest?
Health effects: ageing, burns, eye damage, immunity and cancer risk
How to protect your skin: practical daily steps and reading labels
Sources and medically reviewed guidance
FAQ

What is ultraviolet radiation and its three bands?

Ultraviolet (UV) radiation is invisible energy from the sun that sits just beyond violet light on the electromagnetic spectrum, spanning roughly 100 to 400 nanometres. It splits into three bands: UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm). UVC carries the shortest wavelength and the most energy, but the ozone layer absorbs nearly all of it before it reaches us. That’s why your everyday sun exposure is really a conversation between just two bands—UVA and UVB—not three.

UVA rays: properties, penetration and typical effects

UVA makes up the vast majority of the ultraviolet radiation that reaches the Earth’s surface. Its longer wavelength lets it slip through clouds, glass, and deep into the dermis, the skin layer that holds your collagen and elastin. That’s why UVA is the main driver of premature ageing: fine lines, sagging, and sun spots that show up years after the exposure that caused them.

UVA doesn’t announce itself. You won’t feel it burning, which is exactly what makes it so easy to underestimate.

Present at consistent strength all year round, unlike UVB, which fluctuates more by season.
Passes through most window glass, so office workers and drivers are still exposed.
The dominant ray type in tanning beds, which offer no safer alternative to sunlight.
Linked to indirect DNA damage and some skin cancers alongside its ageing effects.

Pro Tip: If you sit near a window at home or in the car for long stretches, that’s UVA exposure clocking up quietly. A broad-spectrum balm applied in the morning covers you even on days you never step outside.

UVB rays: properties, surface effects and immediate dangers

UVB makes up a much smaller portion of ground-level UV, but it carries far more energy per photon than UVA. That energy is absorbed largely in the epidermis, your outer skin layer, which is why UVB is the ray responsible for sunburn and the most direct form of UV-related DNA mutation.

Diagram comparing UVA vs UVB rays and effects

UVB intensity swings dramatically with the clock and calendar. It peaks between 10am and 4pm and is strongest in summer, which is why a lunchtime walk in July carries far more UVB risk than the same walk in November. UVB also triggers vitamin D synthesis in the skin, though brief, incidental exposure during normal daily life is usually enough for that process; it isn’t a reason to skip sunscreen. Tanning beds emit concentrated UVB alongside UVA, and dermatologists are consistent on this point: no tanning bed is a safe way to get colour.

A short note on UVC

UVC has the shortest wavelength and highest energy of the three bands, but the atmosphere filters it out before it reaches ground level. You’ll only encounter it from artificial sources like germicidal lamps, not sunlight.

When and where is UV strongest?

UV exposure isn’t constant. Several environmental factors push it higher:

Time of day: UVB peaks between 10am and 4pm.
Season: summer months bring stronger UVB; UVA stays fairly steady year-round.
Latitude and altitude: closer to the equator and higher above sea level means more UV.
Reflective surfaces: water, sand, snow, and even concrete bounce UV back at you, so shade never means zero exposure.

The UV Index gives a daily rating of expected UV strength, but daily protection matters regardless of that number, because damage accumulates over years, not single high-index days. Cloud cover blocks some UVB but lets much of the UVA through, and glass behaves the same way, filtering UVB more effectively than UVA.

Health effects: ageing, burns, eye damage, immunity and cancer risk

Short-term harm shows up fast: sunburn from UVB, and photokeratitis (a painful, temporary burn to the eye’s surface) from overexposure to either band. The cumulative effects run deeper. Photoageing from UVA builds over decades. Both UVA and UVB contribute to skin cancer risk, and UVB in particular is effective at suppressing immune activity in the skin, meaning the damage isn’t limited to what you can see in the mirror.

Cataracts are another long-term consequence of unprotected UV exposure to the eyes. Children face a specific version of this risk: a child’s eye can transmit substantially more UVA through to the retina than an adult’s, which is one reason proper sunglasses matter earlier than most parents assume, not just a hat.

Tanning beds deserve a direct mention here. Dermatologists and cancer researchers are unambiguous that tanning beds mirror, and often intensify, the same harms as unprotected solar exposure. There’s no version of an indoor tan that sidesteps the biology.

How to protect your skin: practical daily steps and reading labels

Protection works best as a routine, not a one-off decision on sunny days. Here’s the order that actually holds up:

Seek shade when you can, particularly in the middle of the day, remembering that reflective surfaces still reach you.
Cover exposed skin with clothing and a wide-brimmed hat where practical.
Wear sunglasses that block UV, not just tinted lenses.
Apply broad-spectrum sunscreen SPF 30 or higher, roughly 30 minutes before you head out.
Reapply every two hours, or immediately after swimming or heavy sweating.

Reading a sunscreen label properly makes a real difference. Broad-spectrum means the product protects against both UVA and UVB, which matters because SPF numbers only measure UVB defence. Some products carry a separate UVA rating, such as a circled “UVA” mark or a star system, to indicate how well they handle the other band. A high SPF with no broad-spectrum claim can still leave you exposed to the ray doing the most long-term ageing damage.

On amounts: most adults need roughly a teaspoon for the face and neck, and about a shot glass’s worth for the body, applied generously rather than rubbed in thinly. A quick label checklist:

Does it say “broad-spectrum”?
What’s the SPF number, and is it 30 or above?
Is it water-resistant, and for how long?
Does it carry a UVA star rating or PA mark?
Does it specify reapplication guidance?

Fierce Nature takes the same broad-spectrum principle and applies it to a natural sun balm built without the synthetic filters found in many conventional formulas, an approach explained further in our piece on natural sunscreens in the UK.

Sources and medically reviewed guidance

The claims in this article rest on established public health guidance rather than opinion. The World Health Organization and the CDC both publish detailed breakdowns of the UV spectrum and its documented health effects, including the immune-suppressing role of UVB and the mechanisms behind photoageing. The NHS frames daily sun protection as a year-round habit rather than a summer-only concern, precisely because UVA exposure doesn’t pause for cloudy days or cooler months.

Clinical and dermatological literature consistently links cumulative UV exposure, from both UVA and UVB, to melanoma and non-melanoma skin cancers, and organisations including Cancer Research UK have been explicit that tanning beds carry the same risks as unprotected solar exposure, not a safer substitute. A dermatology-focused resource, the Enriched Med Spa guide on daily sunscreen use, reinforces the same point from a clinical skincare perspective: consistency matters more than any single high-UV day.

None of this is designed to alarm you. It’s designed to make the daily habit feel worth keeping, even when the sky looks grey and the risk feels invisible.

Why daily protection is non-negotiable for us

We built Fierce Nature because harsh, chemical-laden products caused real reactions on real skin, mine included, growing up. Daily sun protection deserves the same scrutiny: it should defend your skin without introducing new irritants. Our tallow-based formulas are made to nourish while they protect, so you’re never trading one skin problem for another. Explore our full balm range to see what that looks like in practice.

A non-toxic option for everyday sun protection

If you’re looking to build broad-spectrum protection into your routine without synthetic filters or a long ingredients list you can’t pronounce, our Sun Balm SPF 50 is worth a look. It’s formulated on our organic tallow base, the same skin-food foundation behind everything we make, so it works with your skin rather than sitting on top of it. We’re not claiming it outperforms every product on the shelf, only that it gives you broad-spectrum coverage without the trade-offs that sent many of our customers looking for an alternative in the first place. Visit the product page to check the details and see if it fits your routine.

FAQ

Is UVA or UVB worse for your skin?

Neither is strictly “worse”, they cause different harm. UVB burns and drives direct DNA damage linked to cancer, while UVA causes deeper, cumulative ageing damage that’s harder to notice until years later.

Is it UVA or UVB that makes you tan?

Both contribute to tanning. UVB triggers the skin’s initial pigment response, while UVA causes the pigment already present to darken, which is why tanning beds that rely heavily on UVA still produce colour.

Do you get vitamin D from UVA or UVB?

Vitamin D synthesis is triggered by UVB exposure on the skin. Brief, incidental daily exposure is typically enough, so it isn’t a reason to skip sunscreen.

Can UVA and UVB pass through windows?

UVA passes through most standard window glass largely unfiltered, which is why UVA exposure continues indoors near windows or while driving. UVB is mostly blocked by glass.