Sunscreen
Most dermatologists recommend SPF of?
15 or greater to all patients regardless of skin type.
Theoretically, SPF 15 allows
15 x longer sun exposure without burning
UVA
95% of solar radiation; Penetrates skin deeper than UVB; Causes indirect damage to DNA; Free radical formation; Damage to cellular membranes
Sunscreen types Divided into
chemical absorbers and physical blockers.
Only one truly effective UVA absorber in the U.S. is
avobenzone
SPF decreases with?
exposure to UV
Chemical sunscreens typically aromatic compounds that Absorb
high intensity UV rays, producing excitation to a higher energy state. Return to the ground state results in conversion of absorbed energy to longer, lower energy wavelengths
Sunscreen MOA
ingredients absorb UV energy; Usually the energy is radiated back to the environment as heat or Some dissipate energy by breaking down chemically
SPF is the time period you can
stay in the sun without burning based on your skin complexion.
SPF =
sun protection factor
in the U.S. UVA protection is limited
"UVA/UVB protection," "Broad-Spectrum"; Based on the presence of certain weak UVA absorbers
UVB
1000 x more effective at producing sunburn than UVA; Causes direct damage to DNA
Oxybenzone
Considered a broad-spectrum UVR absorber; Significantly augments UVB when used in combination
Titanium Dioxide
Ideal sunscreen; Chemically inert; Safe; Blocks full UV spectrum
Sunscreen monograph
Ingredients, formula testing, finished product labeling regulated
"Water-resistant" sunscreen
Maintains the SPF level after 40 minutes of water immersion.
"Very water-resistant" , formerly "water-proof" sunscreen
Maintains the SPF level after 80 minutes of water immersion
Sunscreens Regulated by FDA as
OTC drugs
Avobenzone
Often referred to by its trade name, Parsol 1789; Probably the best UVA absorber; Used with UVB absorbers for broad-spectrum coverage
"Broad or Full-Spectrum" Sunscreen
Protects against UVB and UVA
Physical Blocker Sunscreen
Reflect or scatter UVR
Sunscreen Prevents the following
Sunburn, Skin or lip damage, freckling, skin discoloration, Skin aging, Skin cancer, Phototoxic or photoallergic drug reactions, Photosensitivity diseases
Examples of Sunscreen Physical blockers
Titanium dioxide; Zinc oxide
UVA further broken down:
UVAI- 340-400 nm; UVAII- 320-340 nm
Zinc Oxide
Works as well as titanium dioxide
Sunscreen effectiveness
reduce AK's and solar elastosis; Help reduce drug photosensitization and photo-induced or aggravated dermatoses