UV Filters, SPF and PA+++ How Sun Protection Works
Sunscreen products are designed to protect the skin from ultraviolet (UV) radiation, one of the main causes of photoaging, pigmentation, and cellular damage. To choose such products correctly, it is important to understand SPF, PA+++, and the types of UV filters.
1. Types of UV radiation
Solar UV radiation is divided into three types:
UVA rays
- Penetrate deep into the skin
- Cause photoaging, loss of elasticity, and pigmentation
- Present year-round, even through clouds and glass
- Considered the main factor of skin aging
UVB rays
- Affect the superficial layers of the skin
- Cause redness and sunburn
- Stronger in summer and during daytime
- Play a key role in sunburn formation
UVC rays
- Almost completely blocked by the Earth’s atmosphere
- Not a concern in everyday conditions
2. What SPF means
SPF (Sun Protection Factor) indicates the level of protection against UVB rays.
Approximate values:
- SPF 15 — blocks about 93% of UVB
- SPF 30 — about 97%
- SPF 50 — about 98%
- SPF 50+ — maximum practical protection
SPF does not indicate “time in the sun”, but the level of UVB protection.
3. What PA+, PA++, PA+++ means
PA rating indicates protection against UVA rays, based on the Japanese PPD system (Persistent Pigment Darkening).
- PA+ — low UVA protection
- PA++ — medium protection
- PA+++ — high protection
- PA++++ — very high protection
More plus signs mean stronger protection against photoaging.
4. Types of UV filters
Sunscreens use two main types of filters.
Physical (mineral) filters
Main ingredients:
- Zinc Oxide
- Titanium Dioxide
Characteristics:
- Reflect and scatter UV radiation
- Suitable for sensitive skin
- Less likely to cause irritation
- May leave a white cast
Chemical (organic) filters
Examples:
- Avobenzone
- Octocrylene
- Modern filters such as Tinosorb
Characteristics:
- Absorb UV radiation and convert it into heat
- Lightweight texture
- No white cast
- May cause sensitivity in some individuals
5. Why UVA and UVB protection is important
Modern research shows that UVA radiation plays a major role in skin aging, not only UVB-induced burns.
Effects of UVA exposure:
- Collagen breakdown
- Wrinkle formation
- Loss of skin elasticity
- Pigmentation spots
Effective sun protection must cover both UVA and UVB radiation.
6. How to choose sunscreen
For daily city use:
- SPF 30–50
- PA+++ or higher
For beach or prolonged sun exposure:
- SPF 50+
- PA++++
- Water-resistant formula
For sensitive skin:
- Mineral-based filters are preferred (Zinc Oxide and Titanium Dioxide)
7. Common mistakes
- Applying too little product
- Not reapplying every 2–3 hours
- Using only SPF without UVA protection
- Assuming SPF 50 means full protection
- Skipping sunscreen in winter
Conclusion
SPF indicates protection against UVB (sunburn), while PA indicates protection against UVA (photoaging). An effective sunscreen should protect against both types of radiation and be used year-round.