Sun Protection

Admin on Jan th, 2019

There are few types of wavelength that will damage our skins.
A.    UVC (290-200 nm) - is highly carcinogenic, but is mostly absorbed by the ozone-rich
                                           stratosphere.                  
                                           - with ozone depletion, UVC radiation may become a more important 
                                             factor in skin cancer in the future.                
B.   UVB (315-290 nm) - is responsible for sunburn and can induce skin cancer.
C.   UVA (400-315 nm) - There are a long wave and short wave UVA in our life. Longwave UVA is
                                           what we focus, it can pass through Epidermis to Dermis, cause serious
                                           and  irreversible damage to the skin.
                                         - is responsible for actinic (aging and darkness) damage to the skin and can act as a
                                             co-carcinogen with UVB radiation.               
D.    Blue Light – with the longest wavelength, it can pass to the deepest Hypodermis to your skins
                             , during research, it will cause ROS and RNS in damaging your skin.    
     ※ The oncogenic effect occurs as a result of photochemical damage to epidermal cell DNA
          , damage to DNA repair mechanisms and suppression of cell-mediated immunity. 
Ps. With the longest wavelength, the more pass your skins. But the energy is lower with wavelength.

Damages
A.    UVA – Cause immune resists and related to melanoma.
B.     UVB - ① Cause squamous cell carcinoma
                   ② Damaging DNA ⇒ Let pyrimidines from dimer and cyclobutane pyrimidine dimer.
    ※ The stratum corneum reflects radiation, so reducing the exposure dose.
 
    ※ SPF – Sun Protection Factor
             ↳ only estimate UVB, not UVA
         PA – Protection Grade of UVA
              ↳ only estimate UVA, not UVB
    ※ Water resist – in water 40 mins, still have SPF function.
         Very Water resist – swim 20 mins, 4 times for 80 mins, still have SPF function
         There is no “Water Proof” ⇒ Not only one have this classification

Classification
A.    Physical Sunscreens = Barrier Sunscreens ⇒ Less Sensitive.
           ↳  ① Reflect or Block UV and IR
               ② Only get certified by FDA ingredient ⇒ avobenzone
               ③ Disadvantage ⇒ Metal may produce free-radical
 
B.     Chemical Sunscreens
           ↳ ① Absorb UV itself
        ※    Having sunlight help Vitamin D synthesis
                 ↳ Position ⇒ Keratinocytes
                     ↳ Pro-D3 (7-dehydrocholesterol)
                         ↳ Pro-D3 β ring be photolysis
                             ↳ Pre-D3
                                ↳Thermal Transformation
                                    ↳ Vitamin D3
 
※    Photoaging
            ↳ Inflammation → sun-burning → cell destroy

                              ↑                             ↓                                
                 IL-1.6.8         →   keratinocyte activated, producing free-radical, ex: AP-1 
                  (IL-1α)  
↑         →   keratinocyte activated, producing free-radical, ex: AP-1 
 
※   Dyspigmentation

            ↳ UVA ⇒ Stimulate Granulocyte Monocyte Colony Stimulating Factor
                            ↳ Melanin Produced.
            ↳ Sun exposure increases the activity of melanocytes, the number of melanosomes
                 produced and the rate of transfer of melanin to the epidermal keratinocytes.