Sun protection involves using skincare, clothing, and lifestyle measures to shield the skin from harmful ultraviolet (UV) rays, including UVA and UVB. Broad-spectrum sunscreens are formulated to help protect against both UV ray types, which are associated with burning and visible signs of ageing.
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While the importance of wearing sunscreen daily is well established, it still amazes me that consumers are focused only on the SPF rating of their sunscreen. SPF is only half of the solution to sun protection, and only measures burning rays or UVB rays. SPF is a mathematical equation indicating how long you can stay out in the sun without turning red and does not measure your sun protection from UVA rays.
In this blog, we break down the difference between UVA vs UVB, the difference between physical and chemical sunscreens, and how to get the most out of your SPF.
What is UV radiation?
Ultraviolet (UV) radiation is part of the invisible light spectrum that reaches the Earth from the sun. These wavelengths are then classified into three categories: UVA, UVB, and UVC. Thankfully, lethal UVC rays are filtered by our precious ozone layer, but UVA and UVB protection is vital. Sunscreens shielding us from the damage from both these types of rays are referred to as ‘broad-spectrum’.
What is the difference between UVA and UVB rays?
What is UVA? UVA rays are associated with deeper skin damage and skin ageing (think ‘A’ for ‘Ageing’). UVA is easy to underestimate, because these invisible rays reach more deeply into the skin and are present year-round.
What is UVB? They’re shorter-wavelength rays that affect the surface layers of the skin (think ‘B’ for burning). These are the rays responsible for sunburn, and they are most intense between 11am and 2pm. While UVB damage is more immediately visible, it is no less important to protect against.
UVA vs UVB: at a glance
UVA | UVB | |
Wavelength | Longer | Shorter |
Skin penetration | Deep (dermis) | Surface (epidermis) |
Primary effect | Visible ageing | Burning, surface damage |
Reaches Earth? | Yes | Yes |
Consistent throughout the day? | Yes | Most intense 11am to 2pm |
Can penetrate glass? | Yes | Mostly no |
Proportion of UV reaching earth | ~95% | ~5% |
What is the difference between chemical and physical sunscreens?
I am concerned that consumers are not aware of the difference between physical and chemical sunscreens. Chemical sunscreens (or organic sunscreens) absorb beneath the skin surface and act by absorbing UV light and dissipating the energy as heat. Physical sunscreens (such as zinc oxide and titanium dioxide minerals) sit on top of the skin. They are not absorbed into the bloodstream, and they provide a protective barrier to UV light where they reflect, scatter, and absorb UVA and UVB light. For those with sensitive or reactive skin, a well-formulated physical sunscreen is often the more comfortable and better-tolerated option.
Physical vs chemical sunscreens: a quick comparison
Chemical (Organic) | Physical (Mineral) | |
How it works | Absorbs UV and converts to heat | Reflects and scatters UV light |
Key actives | Oxybenzone, avobenzone, octinoxate | Zinc oxide, titanium dioxide |
Absorbed into skin? | Yes | No |
Suitable for sensitive skin? | May cause sensitivity in some | Generally yes |
Environmental considerations | Some actives flagged for aquatic contamination | Environmentally conscious options available |
Broad-spectrum coverage | Depends on formula | Yes (zinc oxide especially) |
Finish | Typically sheer | Can leave a white cast (varies by formula) |
Which sunscreen should you choose?
Any sunscreen is better than none at all, but given the choice, my advice is to opt for a physical sunscreen containing zinc oxide, as it is a natural mineral that helps protect against harmful UVA and UVB rays. Next time you purchase sunscreen, look for the terms ‘UVB/UVA protection’, or ‘broad-spectrum protection’. Always check the label and ingredient list before you make a purchase.
How to apply sunscreen correctly
Step 1 — Apply last in your morning routine: Sunscreen should always be the final step of your skincare routine, applied before makeup and after any serums or moisturisers.
Step 2 — Use enough product: Most people under-apply. A full face and neck typically requires about a teaspoon of product to achieve the level of protection indicated on the label.
Step 3 — Apply to dry skin: Apply a few minutes before sun exposure to allow the formula to settle properly on the skin.
Step 4 — Reapply every two hours: Reapply during sun exposure and immediately after sweating or swimming.
H2: The bottom line on sun protection
SPF alone is not the full picture. Knowing the difference between UVA and UVB and understanding what your sunscreen products actually contain is what makes sun protection actually work.
If you are looking for a place to start, I recommend exploring Synergie Skin’s solar and environmental skincare. From moisturisers with daily environmental support to antioxidant serums designed to defend against everyday environmental exposure, there is something in the range for every routine.
Not sure what products are suitable for your skin type? Head to our Analyse Your Skin quiz to find your routine or book a free virtual consult with one of our skin therapists today.
FAQs
Why is broad-spectrum sunscreen important?
SPF only measures protection against UVB rays. A broad-spectrum sunscreen provides protection against both UVA and UVB rays, which means more complete coverage against the full range of UV damage, including both surface burning and deeper skin changes associated with ageing.
What is the difference between physical and chemical sunscreens?
Physical sunscreens use actives like zinc oxide or titanium dioxide, which sit on the skin’s surface and reflect UV light. Chemical sunscreens use organic compounds that absorb UV light and convert it to heat within the skin. Physical sunscreens are typically better tolerated by sensitive skin and are not absorbed into the bloodstream.
How often should I apply sunscreen?
As a general guide, sunscreen should be applied every two hours during sun exposure and reapplied after swimming or sweating. Apply it as the last step of your morning skincare routine, before makeup.
Disclaimer: This content is intended for general informational purposes only and does not constitute medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before starting any new health, wellness or therapeutic product or treatment. Individual results may vary.
