Skin Skincare University

Why do you need sunscreen every day?

LEVEL 1 UV and Photoaging Science
KAIAN R&D Team | |

"It's cloudy today, so I don't need sunscreen." "I'm indoors, so I'll be fine." — Have you ever thought something like this?

In reality, UV rays reach the ground even on cloudy days. On lightly overcast days, approximately 80-90% of UV radiation still reaches the earth's surface. Window glass also allows most UVA to pass through.

80% of skin aging is caused by UV rays

According to dermatological research, approximately 80% of skin aging (wrinkles, dark spots, sagging) is caused by "photoaging" from UV radiation. Natural aging due to chronological age actually accounts for only about 20% of total skin aging.

In other words, sunscreen is not something you apply "to avoid getting tanned" — it is something you apply every day "to prevent skin aging".

UVSPFSkinSunscreen = Defense against photoagingUV rays reach your skin on cloudy days and even indoors

Basic guide to choosing sunscreen

For daily use, choose sunscreen with SPF 30 or higher and PA+++ or higher. SPF measures protection against UVB (short-wave UV), while PA indicates protection against UVA (long-wave UV).

Higher numbers don't necessarily mean better. What matters most is "applying the right amount every day and reapplying regularly." Rather than applying once in the morning and forgetting about it, reapplying every 2-3 hours maintains its effectiveness.

Sunscreen is the simplest and most effective form of anti-aging care. Why not make sunscreen a daily habit starting today, regardless of weather or season?

References

Key peer-reviewed sources behind the scientific statements in this article.

  1. Flament F, Bazin R, Rubert V, Simonpietri E, Piot B, Laquieze S. Effect of the sun on visible clinical signs of aging in Caucasian skin. Clin Cosmet Investig Dermatol. 2013;6:221-232. PubMed
  2. Fisher GJ, Wang ZQ, Datta SC, Varani J, Kang S, Voorhees JJ. Pathophysiology of premature skin aging induced by ultraviolet light. N Engl J Med. 1997;337(20):1419-1428. PubMed
This article is reference information about cosmetic ingredients and does not guarantee efficacy. Figures and test results vary by condition.
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