If you do one thing for your skin, this is it. Sun exposure is responsible for the large majority of visible skin ageing — the lines, the uneven tone, the loss of firmness people spend a great deal of money trying to reverse afterwards.

No cream in any catalogue does as much as not accumulating the damage in the first place.

What the numbers mean

SPF measures protection against UVB — the rays that burn.

  • SPF 30 blocks roughly 97% of UVB
  • SPF 50 blocks roughly 98%

The jump from 30 to 50 is small. The jump from nothing to 30 is enormous.

UVA protection is the other half and is not in the SPF number. UVA penetrates deeper, does not burn, and is the main driver of ageing. Look for a broad-spectrum marking, a UVA seal, or "PA" ratings — without it, a high SPF is only doing half the job.

Mineral or chemical

Mineral (zinc oxide, titanium dioxide) sits on the surface, works immediately, and is generally better tolerated by sensitive and reactive skin. Can leave a white cast.

Chemical filters absorb into the skin, feel lighter, and leave no cast. Slightly more likely to sting sensitive eyes.

Neither is better. The one you will actually wear is better.

How much, and how often

Most people use a quarter of what they should. The reference amount for the face is roughly two finger-lengths of product.

Reapply every two hours in strong sun, and after swimming or heavy sweating. Under normal indoor conditions, a morning application is a reasonable compromise.

The excuses worth dropping

"It's cloudy." UVA passes through cloud largely unchanged.

"It's winter." Reduced, not absent — and snow reflects a substantial amount back at you.

"I'm indoors." UVA passes through window glass. If you sit by a window, you are being exposed.

"My foundation has SPF." Almost nobody applies foundation thickly enough to reach the stated protection.

Fitting it into a routine

Last step in the morning, after moisturiser, before makeup. Gel and fluid textures suit oily skin; cream ones suit dry.

The best sunscreen is the one whose texture you do not mind, because daily use over decades is where the benefit is.

For type-appropriate routines, see the skincare section.