The biggest cause of skin aging: UV rays | Why you must wear sunscreen
2026.08.10
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1. UV rays are not only present on sunny days
Many people think that sunscreen is only necessary in the summer when the sun is strong. However, UV rays exist throughout all four seasons, and a significant amount reaches the ground even on cloudy days.
Even indoors, UVA rays that enter through windows can continuously affect the skin, so wearing sunscreen is helpful even if you are going out for a short time.
2. The effects of UV rays on the skin
Skin aging
One of the biggest external causes of wrinkles, loss of elasticity, and sagging skin is UV rays. This is called 'Photoaging'.
Pigmentation
Melasma, freckles, and blemishes can become darker with repeated UV exposure.
Skin barrier damage
Strong UV rays can dry out the skin and increase sensitivity, which may lead to redness or irritation.
Increased risk of skin cancer
Long-term, repeated exposure to UV rays can increase the risk of developing skin cancer.
3. What are SPF and PA?
SPF: The degree of protection against UVB (skin burns)
PA: The degree of protection against UVA (skin aging)
For daily life, SPF 30-50 and PA+++ or higher is usually sufficient.
4. How to apply sunscreen properly
✔ Apply 15-30 minutes before going out
✔ Use a sufficient amount on the face and neck
✔ Reapply if you sweat a lot or have been in the water
✔ Reapply every 2-3 hours during long outdoor activities
5. Common misconceptions
"I'm just staying home, do I need to apply it?"
→ UVA rays can enter indoors through windows.
"My makeup has SPF, is that enough?"
→ It is often difficult to reach the recommended amount using only makeup products.
"Is it not necessary in winter?"
→ UV rays exist regardless of the season.
Conclusion
Sunscreen is not just a cosmetic product to avoid the sun; it is the most basic skincare step to prevent skin aging and pigmentation and to protect skin health.
A small habit of applying sunscreen every morning can make a big difference in your skin years later.