Sunscreen is the highest-return product in any routine and the one most consistently used wrong. These are the six mistakes that matter, in order of how much protection they cost you.
1. Not using enough
This costs more protection than everything else combined.
SPF is measured in a lab at 2mg per square centimetre of skin. For a face and neck that is roughly:
- Two finger-lengths — product squeezed along the full length of your index and middle fingers, or
- A generous half-teaspoon
Most people apply about a quarter of that. Protection does not scale linearly: applying a quarter of the tested amount drops an SPF 50 to somewhere around SPF 15 in practice.
Measure it against your fingers once. It will look like far too much. It is not.
2. Skipping reapplication
Sunscreen filters degrade in UV light and rub off on hands, phones and clothing. A morning application is not protection at 4pm.
- Outdoors or near a window: every two to three hours.
- Indoors, away from windows: once in the morning is genuinely fine. The panic about reapplying at a desk is overdone.
- After swimming or sweating: immediately, whatever the bottle says about water resistance.
Over makeup, a powder or stick SPF is the practical answer. It is not as good as reapplying properly, and it is far better than nothing.
3. Missing the same places every time
The commonly-missed spots, in rough order of how often they show sun damage:
- Ears — especially the tops and the front edge.
- Neck and the back of the neck.
- Chest, if anything you wear is open at the front.
- Backs of hands — the classic tell of long-term sun exposure.
- Eyelids — use a mineral formula if liquid sunscreens sting.
- The hairline and any parting.
4. Trusting the SPF in your makeup
A foundation with SPF 20 is not delivering SPF 20. Foundation is applied far more thinly than the tested amount, and the real protection is usually a small fraction of the number on the bottle.
Treat SPF in makeup as a bonus. Wear a dedicated sunscreen underneath.
5. Ignoring the PA rating
SPF measures UVB — the wavelength that causes burning. It says almost nothing about UVA, which penetrates deeper, drives pigmentation and photo-ageing, and passes through window glass.
Look for a PA rating (PA+ to PA++++) or the words "broad spectrum". PA++++ is the highest. An SPF 50 with no UVA protection is protecting you from sunburn and not from the thing that is actually causing your dark spots.
This is also the answer to "why isn't my pigmentation treatment working": UVA through a window, every day, refilling the pigment as fast as the serum fades it.
6. Choosing a sunscreen you dislike
The best sunscreen is the one you will actually put on, generously, every morning. If yours leaves a white cast, feels greasy or stings, you will use less of it and skip it on rushed days — and that costs more protection than any difference between two well-made formulas.
Modern chemical filters have largely solved the white cast problem for most skin tones. If your only experience is a chalky mineral sunscreen from years ago, the category has moved on considerably.
Chemical vs mineral, briefly
Neither is safer or more effective. Modern broad-spectrum chemical filters are well studied. Choose on how it feels, because that is what determines whether you use it properly.
Frequently asked
Two finger-lengths, or a generous half-teaspoon, for face and neck. Most people apply around a quarter of that, which reduces an SPF 50 to roughly SPF 15 in real-world protection.
If you are near a window, yes — glass blocks most UVB but far less UVA, which is the wavelength that drives pigmentation and ageing. Away from windows, a single morning application is fine.
Neither is inherently better. Mineral filters are often gentler for reactive skin; modern chemical filters are lighter and leave less cast. Choose the one you will apply generously every day, because how much you use matters far more than which type it is.
