Sunscreen: Reading the Label and Actually Using Enough

Sunscreen is the skincare product with the clearest evidence behind it and the one most commonly used wrong. The main failure is not choosing the wrong bottle — it is applying far less than the amount the number on the front assumes.

What the numbers mean

• SPF measures protection against the radiation primarily responsible for burning. It is tested at a specific application thickness, and using less gives you meaningfully less protection than the number implies.
• Broad spectrum indicates protection across a wider range, including the longer wavelengths associated with ageing rather than burning. A high SPF without broad-spectrum protection covers only part of the problem.
• Water resistance is stated as a time period, not as a permanent property. After that period, or after towelling, it needs reapplying.

Rating systems and label wording differ between countries, so a product bought abroad may describe its protection in an unfamiliar way. The underlying test is what matters, not the format of the claim.

Mineral or chemical filters

Mineral filters sit on the surface and reflect; chemical filters absorb. Both work. The practical differences:

• Mineral — less likely to sting sensitive skin or eyes, more likely to leave a white cast, generally thicker.
• Chemical — lighter, more cosmetically elegant, more likely to irritate very sensitive skin.

Which filters are approved differs by country, which is why sunscreens from some markets have textures unavailable elsewhere. Neither category is inherently better; the one you will actually apply every day is better than the one you avoid because it feels unpleasant.

How much, and how often

The tested amount is more than most people use — roughly a generous two-finger length for the face and neck, and considerably more for a body. Applying half gives you substantially less than half the stated protection.

Reapply every couple of hours in direct sun, and after swimming, sweating or towelling. Reapplying over makeup is awkward, which is why powder and spray formats exist — they are easier to reapply and harder to apply thickly enough the first time, so they work better as top-ups than as the base layer.

Choosing one you will use

The main reason people skip sunscreen is that it feels heavy, stings, or sits badly under makeup. Those are legitimate reasons to change product rather than to stop. Formulations vary enormously in texture at the same protection level, so trying a small size before committing is worth the slightly higher unit price.

Storage and shelf life

Sunscreen degrades with heat and time. A bottle left in a car through summer should not be relied on next year. Check the expiry date, and note the period-after-opening symbol — the value size is only good value if you finish it within that window, and most people do not.

Before you order

Check the expiry date on discounted stock, since short-dated stock is a common reason for a reduction and is fine if you will use it in time. Check whether the product is broad spectrum rather than only a high SPF number. And buy a small size first if the texture matters to you, because texture is the thing that decides whether the bottle gets used or sits in a drawer.