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Sunscreen: the most important step in skincare

By the Produto Skincare team · Updated on November 4, 2026

Published on November 2, 2026 · 5-minute read

If you could use only ONE skincare product, sunscreen would be the best bet. Few skincare products have studies as strong as sunscreen does, including a randomized trial that ran for several years (Hughes et al., 2013).

Why does it matter so much?

• About 80% of the visible signs of facial aging were linked to the sun in a study of 298 women (Flament et al., 2013)
• Dark spots: in the same study, spots were strongly linked to sun exposure (Flament et al., 2013)
• Skin cancer: in a trial in Australia, the group that applied sunscreen every day had fewer melanomas over the following 10 years (11 versus 22 cases) (Green et al., 2010)
• Anti-aging: in the same Australian trial, people who used sunscreen every day showed 24% less skin aging over 4.5 years than those who used it now and then (Hughes et al., 2013)

UVA vs UVB

Ordinary window glass and car glass block almost all UVB, but some UVA gets through, depending on the type of glass (Almutawa et al., 2013).

Look for "broad spectrum" or "UVA/UVB" on the label: it protects against both.

How much to apply?

• Face: 2 index fingers' length (≈ 1/4 teaspoon)
• Face + neck: 4 fingers
• Body: 30 ml (about a shot glass)

The SPF on the label is measured with a layer of 2 mg per cm² of skin. At the beach, people usually apply only about a quarter of that, and protection drops much more than by half: with half the amount, an SPF 50 delivers something close to SPF 7 (Faurschou et al., 2007).

When to reapply?

• Every 2 hours of sun exposure (Diffey et al., 2023)
• After sweating or swimming
• After drying your face with a towel
• If you spend the day near a window: it is worth reapplying at midday, because some UVA goes through glass (Almutawa et al., 2013)

Best sunscreen by skin type

The products below are sold in Brazil, where this site is based.

Common mistakes

• ❌ "It's cloudy, I don't need it": clouds don't block all UV radiation, and the benefit in studies came from daily use (Hughes et al., 2013)
• ❌ "I only use it in summer": what showed results was using it every day, not now and then (Hughes et al., 2013)
• ❌ "My moisturizer already has SPF": in one study, people who applied a moisturizer with SPF left more areas of the face uncovered, especially the eyelids, than with sunscreen (Lourenco et al., 2019)
• ❌ "I apply it once and it lasts all day": outdoors, you need to reapply (Diffey et al., 2023)
• ❌ "I don't use it indoors": if you sit near a window, some UVA goes through the glass (Almutawa et al., 2013)

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Translated from the Portuguese original. Contains affiliate links. This text has not yet been reviewed by a dermatologist. © 2026 Produto Skincare.