Guide

What does sunscreen do and how do you choose one?

Sunscreen protects your skin from the sun's ultraviolet (UV) rays. Besides preventing sunburn, it is the most powerful tool for reducing dark spots, premature ageing and the risk of skin cancer, which is why a daily sunscreen is the one recommendation almost every dermatologist agrees on.

4 min read Updated: September 24, 2026

At a glance

What it does: Reduces sunburn caused by UVB rays and the dark spots and premature ageing caused by UVA rays
Best for: Everyone; especially people with dark spots, melasma or acne marks and anyone using retinol or acids
When: Every morning as the last step; reapply roughly every two hours when outdoors
Look for: At least SPF 30, a UVA logo or PA+++ and above, a texture that suits your skin
Watch out: Applying too little, relying on one morning application all day, expired products

Where it fits in your routine

What do UVA, UVB and SPF mean?

Two types of ultraviolet rays from the sun reach the skin. UVB rays affect the upper layer of the skin and are the main cause of sunburn. UVA rays go deeper and pass through clouds and glass; they are a major driver of pigmentation, wrinkles and loss of elasticity. Both increase the risk of skin cancer.

SPF (sun protection factor) only measures protection against UVB. Under lab conditions SPF 30 filters about 97% of UVB rays and SPF 50 about 98%. The difference looks small, but it is meaningful in terms of how much radiation reaches the skin; and since most people do not apply enough in real life, a higher SPF gives you a safety margin.

How do you know a sunscreen protects against UVA?

Always check for UVA protection next to the SPF on the label. On products sold in Europe, the letters "UVA" in a circle mean the UVA protection is at least one third of the SPF. Asian products use the PA system: PA+ is the lowest and PA++++ the highest UVA protection. In the US, look for the words "broad spectrum".

SPF 30 and above: the minimum for daily use
SPF 50 and above: for long hours outdoors, if you are prone to pigmentation or if you use retinol or acids
The circled UVA logo, PA+++ / PA++++ or the words "broad spectrum"
Tinted formulas for dark spots and melasma: their iron oxides also protect against visible light

Mineral or chemical?

Sunscreen filters fall into two groups. Mineral (inorganic) filters are zinc oxide and titanium dioxide; they are often preferred for sensitive skin and babies, but they can leave a white cast, especially on darker skin tones. Chemical (organic) filters give lighter, more transparent textures; most sunscreens today combine both groups.

What matters is not which one is better on paper, but which one you will happily apply every day. A sunscreen you avoid using gives no protection, however good it looks on paper.

Choosing by skin type

Texture is the biggest factor in whether you will actually use a sunscreen every day.

Oily and acne-prone skin: gel, fluid or matte-finish products labelled "non-comedogenic"
Dry skin: cream textures with moisturizing ingredients such as glycerin, ceramides or squalane
Sensitive skin and rosacea: fragrance-free, low-alcohol, mainly mineral formulas
Dark spots and melasma: SPF 50+, high UVA protection and ideally a tinted formula
Sport and swimming: water-resistant products; still reapply after towelling

The right amount and how to apply it

The SPF on the label is measured at 2 milligrams per square centimetre. For the face and neck that is roughly a quarter of a teaspoon, or in practice two strips of product along the length of your index and middle fingers. Applying half of that lowers the real protection considerably.

Apply sunscreen as the very last step of your morning routine, after moisturizer and before makeup. Do not forget your ears, neck, the back of your neck and the backs of your hands. When outdoors, reapply roughly every two hours and straight after swimming, sweating or towelling.

SPF compact powders or sprays are handy for topping up over makeup; but on their own they do not provide enough product and cannot replace your morning application.

Common mistakes

Skipping it on cloudy days or in winter: UVA rays do not care about seasons or clouds
Relying on the SPF in foundation or moisturizer: you never apply enough of those
Spending the whole day outdoors on a single morning application
Using last summer's product that sat in the heat or is past its expiry date
Treating a high SPF as permission to stay in the sun longer

FAQ

Do I need sunscreen at home or in the office?

Yes, if you sit near a window for long periods, because UVA rays pass through glass. If you spend the day indoors away from windows, your morning application is usually enough.

SPF 50 or SPF 30?

SPF 30 is enough for most people in daily city life. Choose SPF 50 if you spend long hours outdoors, are prone to pigmentation or use products that sensitise the skin, such as retinol and acids.

Can sunscreen cause breakouts?

Heavy, oily formulas can cause problems on acne-prone skin. Try gel or fluid textures labelled "non-comedogenic" and remove sunscreen thoroughly in the evening; double cleansing works well for oily skin.

When should I apply sunscreen?

A few minutes before going out, as the last step of your morning routine. For chemical filters, applying about 15 minutes before going out is usually recommended.

Can babies use sunscreen?

For babies under six months, shade, hats and clothing are recommended instead of sunscreen. For older children, choose mineral products made for babies and children; if in doubt, ask your paediatrician.

This article is for general information only and is not medical advice. If you have a skin condition, are pregnant or take regular medication, talk to your dermatologist or pharmacist before starting a new product.

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