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Sunscreen Questions Answered

Every morning, as the last step: a broad-spectrum sunscreen of SPF 30 or higher, in a real amount (two finger-lengths for face and neck). Outdoors, reapply every 2 hours and after sweating. Clouds do not block most UV.

Written by the Oliareen editorial teamDermatologist review: pendingLast updated: 6 November 2026How we write

What SPF and PA mean

SPF measures protection from UVB, the rays that burn. Applied properly, SPF 30 blocks about 97% of UVB and SPF 50 about 98%. UVA goes deeper and drives dark spots and sun ageing; "broad-spectrum" or PA+++ / PA++++ on the label means UVA protection too.

  • How much you apply matters more than 30 versus 50.
  • For dark spots, melasma or long hours outdoors, SPF 50 with PA++++ is a sensible pick.

How much to apply

The SPF number is tested at a generous amount (2 mg per square centimetre). Most people apply a quarter to half of that and get far less protection than the label. Simple rule: squeeze two lines along the full length of your index and middle fingers, roughly a quarter teaspoon for face and neck.

When to apply and reapply

  • Last in the morning routine, after moisturizer.
  • About 15 minutes before you go out.
  • Outdoors, every 2 hours, and straight after heavy sweating, wiping or washing your face.
  • Indoors all day, away from windows, the morning layer is usually enough. UVA does pass through window glass.
  • Sprays or cushions make top-ups over makeup easier, though they usually deliver less product.

Do you need it on cloudy days?

Yes. Up to 80% of UV can pass through light cloud (WHO). UV is not heat, so it reaches your skin even when the sun does not feel strong. In Bangladesh the midday UV index is often high even on cloudy monsoon days. When a weather app shows UV index 3 or more, protect your skin.

Rickshaws, buses and walking in the sun

A rickshaw hood shades your head, not the sides of your face or neck, and light also bounces off roads and walls. A bus window seat puts more sun on one side of the face. Sunscreen in the morning, plus an umbrella, cap or scarf, and another layer before you head out again in the afternoon.

White cast on brown skin

Zinc oxide and titanium dioxide (mineral filters) can leave a white or grey cast on brown skin, so people apply less and lose protection. Tinted sunscreens with iron oxides hide the cast and add some protection from visible light, which matters for melasma-prone and spot-prone skin. Thin fluids with chemical or hybrid filters are another good option.

  • Apply in two layers: half, blend, then the other half.
  • Do not dodge the cast by using less; switch texture instead.

For oily or acne-prone skin

Gel, fluid or matte-finish sunscreens usually feel less greasy. Sunscreen does not cause acne by default, but heavy, oily formulas can clog pores for some people. Wash it off well at night.

What does not replace sunscreen

  • SPF in makeup or foundation: it is worn far too thinly to give the labelled protection.
  • Vitamin C serum: helpful under sunscreen, but not a sunscreen.
  • Shade, hats, umbrellas and avoiding the strongest midday sun when you can all work together with sunscreen.

Questions people ask

SPF 30 or SPF 50?

SPF 30 is enough for daily use if you apply enough. For spot- or melasma-prone skin or long hours outside, SPF 50 with PA++++ makes sense. The one you will actually wear every day protects you most.

Mineral or chemical: which is better?

Both work. Mineral filters suit some sensitive skin but can leave a white cast. Chemical or hybrid filters are usually thinner and invisible. Choose the one you can apply generously every day.

Does sunscreen stop skin from getting darker?

Sunscreen reduces new tanning and the darkening of spots, and it is the base of any effort to fade marks. It does not change your natural skin tone, and it does not need to.

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Sources

  1. American Academy of Dermatology — How to apply sunscreen
  2. American Academy of Dermatology — Sunscreen FAQs
  3. World Health Organization — Ultraviolet radiation fact sheet
  4. NHS — Sunscreen and sun safety
  5. PRISM-ISF Indian sunscreen consensus 2025 (South Asian skin and climate)
  6. Diffey B. — sunscreen application amount, BMJ 2002
  7. Oliareen research base — visible light and iron-oxide tinted sunscreen in melanated skin (systematic review summary)