SPF: the most important step you are probably skipping

If you do nothing else for your skin, wear sunscreen. Up to 80% of visible facial ageing is caused by ultraviolet light - not genetics, not time. No serum, peel or treatment will out-perform daily SPF.

What SPF actually measures

SPF measures protection against UVB - the rays that burn and cause most skin cancers. SPF 30 blocks about 97% of UVB; SPF 50 blocks about 98%. The jump from 30 to 50 is small in lab numbers but meaningful in real life, because almost no one applies enough sunscreen to achieve the rated SPF.

Look for "broad spectrum" or a UVA seal on European products. UVA is the deeper, ageing wavelength - it penetrates glass and clouds, and it is present all year round.

Chemical vs mineral

• Chemical (organic) filters - modern UK and EU filters such as Tinosorb, Uvinul and Mexoryl are photo-stable, broad-spectrum and cosmetically elegant. They sit in the top layer of skin and absorb UV.
• Mineral filters - zinc oxide and titanium dioxide reflect and absorb UV. Excellent for sensitive, reactive or post-procedure skin, but tend to leave a slight cast and feel heavier.

Both work. The best sunscreen is the one you will actually wear every day.

How much, how often

• Two finger-lengths for face, neck and ears - roughly a quarter teaspoon for the face alone.
• Reapply every 2 hours outdoors, and after swimming or heavy sweating.
• Indoors, daily, year-round. UVA comes through windows and is present even in winter.
• Sunscreen goes on last in your morning routine, after moisturiser and before make-up.

The myths to bin

"I have darker skin, I don't need it." Melanin offers some baseline protection, but UVA still drives pigmentation, melasma and ageing in every skin tone.

"My foundation has SPF 15." You do not apply foundation thickly enough to achieve any meaningful protection. Use a dedicated sunscreen underneath.

"I'm inside all day." Windows block most UVB but very little UVA. If there is daylight, there is UVA.

If you do one thing this month

Find a broad-spectrum SPF 30–50 you actually enjoy wearing - a fluid, a tinted mineral, a hybrid serum-sunscreen - and put it on every morning. Within three months you will see the difference. Within ten years, you will really see the difference.