If there is one beauty and health habit with unanimous scientific backing, it is daily sunscreen use. Ultraviolet radiation is responsible for most premature skin ageing, spots and a large share of skin cancers. And yet many people use it only at the beach, in insufficient quantity or apply it badly. This guide helps you choose it, apply it and keep the habit all year round.

What ultraviolet radiation is

The sun emits several types of ultraviolet radiation. UVB rays are mainly responsible for sunburn, while UVA rays penetrate deeper, pass through glass and clouds and contribute to wrinkles, spots and cell damage. That is why a broad-spectrum product, which protects against both types, is what you want.

What SPF means

The sun protection factor, or SPF, indicates how much protection it offers against UVB. An SPF 30 blocks about 97% of UVB, and an SPF 50 about 98%. The difference seems small, but in fair skin, with a history of skin cancer, or in high-exposure situations, that extra protection counts. Remember that no sunscreen blocks one hundred per cent of radiation or lets you spend hours in the sun without risk.

Physical, chemical and hybrid filters

Mineral or physical filters, such as zinc oxide and titanium dioxide, reflect radiation and are usually well tolerated by sensitive skin; they sometimes leave a whitish film, although current formulas are more cosmetic. Chemical filters absorb radiation and come in lighter, more transparent textures. Hybrids combine both. There is no «best» in general terms: the best sunscreen is the one you like enough to use every day.

How to choose for your skin

  • Oily or acne-prone skin: look for gel, fluid or matte-finish textures, oil-free and labelled non-comedogenic
  • Dry skin: richer creams with moisturising ingredients
  • Sensitive skin: mineral filters and fragrance-free formulas
  • Skin with spots: high protection, SPF 50 and, if possible, tinted or with antioxidants
  • Children: specific sunscreens, preferably mineral, with shade and clothing as the main allies

How much to apply

This is the most common mistake. To obtain the protection stated on the pack, a considerable amount is needed: about two milligrams per square centimetre of skin. In practice, for the face and neck that is two fingers of product, that is, a line of cream along the index finger and another along the middle finger. For an adult’s whole body, we are talking about 30 to 35 millilitres, roughly a small full glass.

When and how often to apply

Apply sunscreen about fifteen or twenty minutes before going out, and repeat every two hours if you are outdoors, and always after swimming, sweating heavily or towelling off. «Water-resistant» sunscreens are not indelible. If you spend the day in the city with limited exposure, one morning application is usually enough, but reapply if you spend time in direct sun.

Do not forget neglected areas

Ears, nape, tops of the feet, lips, bald patches, décolletage and hands are places where sun damage often appears. Use a lip balm with SPF and remember the areas left uncovered when you bend down or move.

Protection in winter and in the city

UVA radiation passes through clouds and glass, and snow reflects much of the rays. That is why it is advisable to use sunscreen daily, even in winter and when driving. The UV index for your area, shown by many weather apps, is a useful guide: from a value of 3, protection is recommended.

Beyond sunscreen

Cream is only one part of protection. Avoid the middle of the day, seek shade, wear a wide-brimmed hat, sunglasses with UV filter and protective clothing. Artificial tanning booths are not a safe option. And check your moles once a month: if one changes shape, colour or size, or bleeds, consult a dermatologist.

Expiry and storage

Many packs indicate a period of use after opening. If the product has changed smell or texture, or has been exposed to heat for a long time, it is better to replace it. Do not leave it in the car or in direct sun. And remember that what is left from last year, if it is still in good condition and within date, can serve you, but the amount applied must always be correct.

Sunscreen and make-up

If you wear make-up, apply sunscreen first, wait a couple of minutes and then apply your products. Foundations or powders with SPF are a nice complement but do not replace sunscreen, because we rarely apply enough to reach the stated protection. If you need to reapply over make-up, mists, sticks and powders with SPF make the job easier without spoiling the finish.

Myths worth leaving behind

Having dark skin does not make you immune to sun damage; it simply offers some natural protection that is not enough on its own. Nor does a base tan protect you: tanning is already a sign of skin damage. And you do not stop needing sunscreen because you take vitamin D supplements: a few minutes of daily exposure of hands and face is usually enough for most people, and your doctor can advise you if you suspect a deficiency.

The most worthwhile habit

Making sunscreen a daily habit, as natural as brushing your teeth, is one of the best decisions you can make for your skin. Over time, prevention shows in fewer spots, fewer wrinkles and, above all, fewer risks to your health.