UVA and UVB Sun protection factor
UVA andUVB Sun protection factor
SPF is Sun Protection Factor. The number is
determined experimentally indoors by exposing human subjects to a light
spectrum meant to mimic noontime sun. The SPF number only relates to UVB protection. UVA is measured by the other definition. UVA protection is not measured through SPF numbers.
PA is the Japanese measurement of sun protection. It is
one of protection grade of UVA . UVA
is based on the Persistent Pigment Darkening (PPD) reaction reading at 2-4
hours of sun exposure. PA is a protective level of strength to mark the
three PA+, PA++ and PA+++.
SPF(sun
protection factor)
- Standard: ISO 2444: 2010 cosmetic sun protection test method in vivo determination of SPF (sun protection factor)
- Test by erythema
- Minimal dose: MED (minimal erythema dose)
- Process: exposure to the UV (wave length 290-400nm)
- Test skin type: type I~ III (ITA0>280)
- Duration: 16-24hrs after exposure
UVA-PF
(UVA protection factor)
- Standard: ISO 24442: 2011- cosmetics-sun protection test methods-in vivo determination of sunscreen UVA protection.
- Test by PPD (persistent pigment darkening)
- Minimal dose: MPPDD (minimal persistent pigment darkening dose)
- Process: exposure to the UV (wave length 320-400nm). calculate the UVA parameter by statistics.
- Test skin type: type II~ IV (200<ITA0>410)
- Duration: 2-4hrs after exposure
PA (Protection Grade of UVA)
PA+ =
2<UVA-PF<4
PA++ =
4<UVA-PF<8
PA+++ =
8<UVA-PF
PA++++ = 16<UVA-PF
PA+ provides some UVA protection with a factor of PPD
2-4. It protects skin against low to medium UV radiation.
PA++ provides moderate UVA protection with a factor of
PPD 4-8. It protects skin exposure to medium UV radiation.
PA+++ provides good
UVA protection with a factor of PPD > 8. It is the strongest grade of UVA
protection now available. It protects skin exposure under very strong or direct
UV radiation.
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