How to Choose Sunscreen: SPF, UVA, UVB and Filter Types

Photoageing describes cumulative skin changes caused by repeated ultraviolet exposure. It can appear as fine and coarse wrinkles, mottled pigmentation or sun spots, rougher texture, loss of elasticity and more visible small blood vessels.

In a community randomised trial, adults assigned to daily broad-spectrum sunscreen showed 24% less progression of visible skin ageing over four and a half years than those using sunscreen at their own discretion [1]. Human skin studies also show that solar UV exposure can reduce type I procollagen production, helping to explain its effect on skin structure [2].

Sunscreen doesn’t need to reverse existing changes to be worthwhile. It reduces the repeated UV exposure that drives further collagen breakdown and pigment production.

UVA has a longer wavelength and penetrates more deeply into the skin. It reaches the dermis, where collagen and elastin sit, and contributes to wrinkles, loss of elasticity and pigmentation. It is present throughout daylight hours and can pass through ordinary window glass.

UVB is absorbed mainly within the epidermis. It is the main cause of sunburn and causes direct DNA damage. Its intensity varies more with season, latitude and time of day.

The memory aid—A for ageing and B for burning—is useful, but incomplete. Both cause long-term damage, so broad-spectrum protection matters more than the SPF number alone [3].

SPF mainly measures UVB protection under standardised test conditions. It does not tell you enough about UVA protection, finish or what happens when you apply less than the tested amount.

I usually favour broad-spectrum SPF 50 for facial use, particularly if you have pigmentation, use photosensitising skincare or spend significant time outdoors. It provides extra margin for imperfect application.

A well-applied broad-spectrum SPF 30 is still effective and may be the better choice if you prefer its texture and therefore apply it generously. In the UK, also look for broad-spectrum wording, a UVA symbol in a circle, or a four- or five-star UVA rating [4].

Mineral filters usually mean zinc oxide and titanium dioxide. They mainly absorb UV, with some scattering and reflection. They can work well for sensitive skin and in tinted formulas, but may leave a cast on deeper skin tones or collect within facial hair.

Chemical filters are more accurately called organic filters. They absorb UV and often allow lighter, clearer formulas. They can be useful if you have a deeper skin tone, facial hair or do not want tint.

Hybrid formulas combine mineral and organic filters. Many modern products use a blend to balance broad protection with a better finish.

No category is automatically best. Broad-spectrum performance, adequate application and cosmetic acceptability matter more than the label.

For melasma, the more useful distinction is often tinted versus untinted.

Visible light can worsen melasma and persistent pigmentation. In a randomised trial, an SPF 50 sunscreen containing iron oxides for visible-light protection improved melasma outcomes more than a similar UV-only sunscreen when both were used alongside hydroquinone [5]. Another randomised study found better prevention of relapse with protection extending into visible light [6].

Tinted mineral-containing formulas often include iron oxides, which is why they are commonly chosen for melasma. An untinted mineral sunscreen is not automatically better than an organic-filter formula; the additional benefit comes from suitable visible-light protection and a tint you can apply generously.

Apply enough to form an even film over the face, ears and neck. The two-finger guide—two lines along the index and middle fingers—is a useful approximation for the face and neck, although textures vary.

Use sunscreen as the final skincare step. When outdoors for prolonged periods, reapply at least every two hours and after swimming, sweating or towel drying. Combine it with shade, clothing and hats rather than using it to extend time in strong sun [4].

Choose a sunscreen you can use consistently

SPF 50 is my usual preference, but the most useful formula is not necessarily the one with the highest number or longest ingredient list. Choose a broad-spectrum sunscreen that you can apply generously and continue using every day.

For melasma, that may be a tinted formula with iron oxides. For dry skin, it may be a richer hybrid cream. For deeper skin tones, facial hair or anyone who dislikes tint, it may be a sheer organic-filter product.

Choose a finish you can use consistently, then apply enough of it.