#Protection of UVB and UVA

Protection of UVB and UVA

Protection of UVB and UVA
The indicator of the sunblock lotion could be divided into for UVB and for UVA. Below is the data by the experiment for differential.
1.      The darker skin, the less suntanned. The MED (minimal erythema dose of 24 hrs exposure under sun)is higher as well.
2.      An example of skin testing
MED of UVB is 20-35 mJ/cm2
MED of UVA is 50000-60000 mJ/ cm2
The results show UVA is not easy to cause erythema. But UVB does.

The visible effectiveness of suntanned is from UVB. UVA causes immediate pigment darkening and disappear after few hours. UVA effectiveness is hard to measure and define in the experiment. But UVA will damage the elastin and collagen in dermis for long term. So the alternative testing is defined by the persistent pigment darkening. 

The erythema results in UVB most of the time. It is meaningless if the lotion only protects UVA. It should be careful the long term suntanned, even if you apply the sun block lotion. You may don’t have erythema in the appearance, but dermis may be damaged already that will accumulate skinaging and wrinkles symptom inside. 

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