If there's one product that does more for your skin than any serum, it's sunscreen. The large majority of visible facial ageing — lines, sagging, uneven tone, rough texture — is driven by UV exposure, and sun protection is the single most effective preventative step you can take. The two big questions people have are which type to use, and what the SPF number actually means.
Physical vs chemical: two ways to block UV
Sunscreens fall into two broad families. Physical (mineral) filters — zinc oxide and titanium dioxide — sit on the skin and work largely by reflecting and scattering UV (with some absorption too). They protect from the moment they're applied and tend to suit reactive, sensitive or post-procedure skin, though they can leave a white cast. Chemical (organic) filters — such as avobenzone, octisalate, homosalate and newer-generation filters like Tinosorb and Mexoryl — absorb UV and release it as a tiny amount of heat. They're cosmetically lighter and easier to wear daily, and the newer filters offer excellent broad-spectrum coverage.
One myth worth retiring: the idea that mineral sunscreens only reflect and chemical ones only absorb. In reality mineral filters absorb a good deal of UV too. The practical point is that both types are effective — the best sunscreen is simply a broad-spectrum one you'll happily apply every day.
Broad spectrum: UVA and UVB
UV comes in two skin-relevant forms. UVB is the shorter wavelength behind sunburn and is strongly linked to skin cancer. UVA penetrates more deeply, drives most photoageing, and passes through glass — so it reaches you indoors and in the car. "Broad spectrum" means a sunscreen protects against both, which is what you want.
What SPF actually means
SPF measures protection against UVB specifically — and, crucially, it is not a linear scale. The jump from no protection to SPF 15 already blocks most UVB; after that the gains shrink quickly.
SPF only describes UVB. For UVA, look for "broad spectrum", a PA rating (PA+ to PA++++) or a UVA logo — not just a high number.
The part that matters most: how you use it
Sunscreen is only as good as the way it's applied, and this is where most protection is lost. Use a generous amount — roughly a quarter-teaspoon for the face and neck; most people apply far too little, which is partly why a higher SPF is a sensible buffer. Apply as the last step of your morning skincare, reapply every two hours of sun exposure and after swimming or sweating, and wear it daily and year-round, since UVA is fairly constant through the seasons. Finally, don't rely on the SPF in your foundation alone — there's rarely enough of it to count.
The verdict
Physical or chemical, the best sunscreen is a broad-spectrum SPF 30 or higher that you enjoy wearing enough to apply properly every single day. Choose mineral if your skin is sensitive or reactive, chemical if you want a lighter feel and no white cast — then focus your energy on applying enough and reapplying. Done consistently, it outperforms almost anything else in your routine.
This article is for general education and is not medical advice.
References
Latha MS, et al. Sunscreening agents: a review. Journal of Clinical and Aesthetic Dermatology, 2013.
Sander M, Sander M, Burbidge T, Beecker J. The efficacy and safety of sunscreen use for the prevention of skin cancer. Canadian Medical Association Journal, 2020.
Young AR, Claveau J, Rossi AB. Ultraviolet radiation and the skin: photobiology and sunscreen photoprotection. Journal of the American Academy of Dermatology, 2017.