UV (ultraviolet) is divided by wavelength into UVA (320–400nm), UVB (280–320nm), and UVC (100–280nm). UVC is mostly blocked by the ozone layer, so UVA and UVB are what affect skin.
UVA vs UVB key differences
| Item | UVA | UVB |
|---|---|---|
| Wavelength | 320–400nm (long) | 280–320nm (short) |
| Nickname | "Aging" UV | "Burning" UV |
| Main effect | Photoaging (wrinkles, pigmentation) | Sunburn, skin cancer |
| Penetration depth | Deep into the dermis | Epidermis |
| Season/weather | Year-round, weather-independent | Strong in summer and on clear days |
| Glass transmission | Passes through (affects indoors) | Mostly blocked |
| Index | PA | SPF |
How UVA causes photoaging
Photoaging refers to skin aging caused by UV. About 80% of all skin aging is photoaging caused by UV (mainly UVA).
When UVA penetrates to the dermis:
- Generates reactive oxygen species (ROS) → cell DNA damage
- Activates collagen-degrading enzymes (MMP) → destroys collagen/elastin
- Stimulates melanin production → melasma, spots, pigmentation
- Damages blood vessels → redness, dilated capillaries
Photoaging vs intrinsic aging
| Item | Intrinsic aging | Photoaging |
|---|---|---|
| Cause | Time, genetics | Cumulative UV exposure |
| Speed | Gradual | Fast |
| Wrinkle type | Expression lines, fine lines | Deep, coarse wrinkles |
| Pigment change | Almost none | Melasma, spots, uneven tone |
| Skin texture | Thinning | Thickened and rough |
| Preventability | Difficult | Largely preventable with sun protection |
How to prevent photoaging
1. Daily sunscreen — not just a summer issue
UVA affects skin year-round, regardless of weather. Even indoors in December, UVA enters through windows. Daily SPF30+, PA+++ sunscreen is essential.
2. Antioxidants for internal defense
If sunscreen is the "external shield," antioxidants are the "internal shield." They neutralize the ROS generated by UVA.
- Vitamin C: use as a morning serum. Antioxidant + melanin suppression + collagen synthesis
- Vitamin E: antioxidant synergy with vitamin C
- Niacinamide: blocks melanin transfer, prevents spots
- Resveratrol, EGCG (green tea): plant antioxidants
3. Supplementary sun-protection measures
- Wide-brimmed hats, UV-blocking sunglasses
- UV-protective clothing (UPF rated)
- Minimize outdoor activity during peak UV (10 a.m.–2 p.m.)
Can existing photoaging be reversed?
Full reversal is difficult, but improvement is possible:
- Retinol/retinoids: stimulate synthesis of collagen destroyed by photoaging, improve wrinkles. The most evidence-backed anti-aging ingredient
- Vitamin C: improves existing pigmentation, supports collagen synthesis
- Niacinamide: reduces melasma and spots
- Dermatology clinic care: IPL, laser resurfacing, Botox, filler
SKINROUTE and photoaging management
The pigment and elasticity indicators in SKINROUTE SKIN100 analysis help assess accumulated photoaging. Your AI coach suggests antioxidant and anti-aging routines suited to your current skin condition.