UVA vs UVB — the short version
In short
UVB = "burn" — short-wavelength radiation that causes redness and sunburn, mostly affects the epidermis, and is directly linked to skin cancer. UVA = "aging" — long-wavelength radiation that penetrates deep into the dermis, damages collagen and elastin, and is active even on cloudy days and through glass.
This distinction matters practically: someone who doesn't burn in the sun isn't necessarily "protected". UVA doesn't cause sunburn — it causes aging. So sunscreen needs to be broad spectrum, meaning it covers both UVA and UVB.
Sunscreens: physical (mineral) vs chemical
Every sunscreen has a mechanism. Two main categories on the market:
Physical / mineral sunscreen
Active ingredients: primarily Zinc Oxide and Titanium Dioxide. Two opaque minerals that sit on the skin's surface and act as light mirrors — reflecting and scattering radiation.
Chemical sunscreen
Active ingredients: Avobenzone, Oxybenzone, Octocrylene, Homosalate and others. They absorb into the skin's outer layer and absorb UV chemically — converting it to heat that dissipates.
| Parameter | Physical / mineral | Chemical |
|---|---|---|
| Mechanism | Reflects and scatters UV above the skin | Absorbs UV and dissipates as heat |
| Onset of protection | Immediate — protected as soon as applied | 15–30 minutes after application |
| Photo-stability | Stable — doesn't break down in light | Some chemicals less stable |
| Irritation and stinging | Low risk — suitable for sensitive skin | Higher risk of sensitivity and stinging |
| Pregnancy-suitable | Yes — safe | Some active ingredients less recommended |
| Suitable for rosacea / melasma | Yes — in fact preferred | Some can trigger flares |
| White cast on skin | More noticeable (less so in modern micro/nano formulations) | Minimal |
| Feel on skin | Sometimes heavier | Usually lighter |
| Coral reef impact | Better ("reef-safer") | Some chemicals banned under reef-protection laws |
Why we recommend physical in most cases: immediate protection, less irritation, photo-stability, and high safety profile in sensitive contexts. The "white cast" downside is largely solved in modern formulations, and in tinted bases matched to skin tone.
If someone can't find a physical formulation that works for their skin (for cosmetic or texture reasons) — a good chemical sunscreen is much better than none. The best sunscreen is the one you'll actually use every day.
Correct use — not just "what to apply" but "how much and when"
- Amount: a full teaspoon for face and neck alone. Most people apply about a third of what's needed — which drops the SPF protection significantly.
- Timing: physical — immediately. Chemical — 15–30 minutes before sun exposure.
- Reapplication: every 2 hours outdoors, and after sweating/swimming/towel-drying.
- On winter and cloudy days: UVA penetrates clouds and glass. A daily sunscreen habit shouldn't depend on the weather.
- Often forgotten: ears, upper chest, back of hands, exposed scalp.
Modifiable vs non-modifiable damage
When discussing skin aging, it's important to separate what you can influence from what you can't. This isn't a theoretical distinction — it determines where to put effort.
Modifiable — you can change it
- Sun exposure — timing of going out, daily sunscreen, shade
- Protective clothing and hats — mechanical protection that's often better than any sunscreen
- Sunglasses with UV protection — protect the thin skin around the eyes from UVA
- Smoking — breaks down collagen, reduces blood flow to skin, accelerates perioral and periorbital lines
- Alcohol — accelerates glycation (protein damage), dehydrates, worsens redness and visible vessels
- Hydration — reasonable water intake through the day supports skin barrier function and appearance
- Sleep — hours and quality affect overnight repair processes
- Nutrition — balance of antioxidants and polyunsaturated fatty acids
Non-modifiable — genetically set
- Skin type (Fitzpatrick) — tendency to burn vs tan, tendency to pigment
- Family history of skin cancer — melanoma, BCC, SCC
- Genetic conditions — familial rosacea, vitiligo, hormonal/genetic melasma
- Individual rate of aging — cellular factors inherited through families
Why this matters
Genetics can't be changed, but they only determine part of the story. Clinical-literature estimates are that modifiable factors — primarily UV exposure and smoking — account for 80–90% of the aesthetic changes attributed to "aging". In other words, most of the damage people see in their skin is damage that could have been prevented, and that can still be slowed going forward.
Building a practical routine
You don't need 12 products. A basic routine that works:
- Morning: gentle cleanse → broad-spectrum physical SPF 30–50 (can be combined with makeup if desired).
- Outdoors in summer: wide-brimmed hat + UV-blocking sunglasses.
- Evening: cleanse + moisturise. For those for whom it's appropriate — retinoid or vitamin C under medical guidance.
- Avoid: smoking, sun exposure between 11:00 and 15:00, intentional tanning.
- Hydration: 1.5–2 litres of water a day, less alcohol especially in the evening.
Our clinical approach: before discussing aesthetic treatments, we want the basic routine in place. Every aesthetic treatment gradually "breaks down" if sun exposure continues unchecked.
FAQ
I'm indoors all day — do I still need sunscreen?
Yes, if there are windows. UVA passes through glass. If you sit near a window, drive in a car, or step outside even briefly — daily sunscreen is recommended. If you're genuinely in a windowless room all day (rare), you can skip it.
Do I need sunscreen on dark skin (Fitzpatrick V–VI)?
Yes. Darker skin burns less but isn't immune: hyperpigmentation and melasma worsen with UV. Skin cancer in darker-skinned populations is often diagnosed later and more aggressively. Physical sunscreen is actually preferred on darker skin because some chemical filters can worsen pigmentation.
Are zinc oxide and titanium dioxide safe in pregnancy?
Neither is significantly absorbed through the skin — they sit on the surface. So they're considered safe during pregnancy and lactation. Some chemical filters (especially Oxybenzone) are less recommended in pregnancy due to potential hormonal activity, which is why physical is the default in pregnant patients in clinical practice.
Is a higher SPF always better?
Not linearly. SPF 30 blocks about 97% of UVB, SPF 50 blocks 98%, SPF 100 blocks 99%. The difference is small. What matters more: quantity applied (most people under-apply), broad spectrum (UVA+UVB), and reapplication. A physical SPF 30–50 applied correctly is better than SPF 100 applied as a thin layer.
If I drink lots of water — will it give me "great skin"?
Adequate water is a foundation for skin function — but not a magic mask. The idea that 4 litres a day dramatically changes the skin isn't well supported. Reasonable hydration (1.5–2 L/day, more in hot climates), combined with reducing alcohol, creates a good baseline — but doesn't replace treatments aimed at specific issues.
Why does smoking damage the skin?
Two main mechanisms: (1) nicotine constricts blood vessels, so less oxygen and nutrients reach the skin; (2) chemicals in the smoke activate enzymes that break down collagen and elastin. On top of that, repeated mouth movements cause earlier perioral wrinkles. In smokers, skin aging is typically accelerated by 10–20 years.
Want to build a protection routine that fits you?
A short consultation can assess your current skin status, identify the relevant damage drivers in your case, and build a simple routine that works — before discussing treatments. No commitment.