Sunscreen and photoprotection Flashcards
Which sunscreens are “organic”
Chemical sunscreens use soluble organic filters (chemical compounds) that absorb UV radiation.
2 main classes of sunscreens?
- chemical sunscreens –> organic molecules which absorb UV light
- Insoluble metal oxide filters “physical” agents which absorb and scatter UV radiation
How is the sun protection factor (SPF) calculated?
Minimal erythema dose (protected / minimal erythema dose (MED) unprotected.
How is water resistance tested?
After application and before MED testing they do 20-min water immersions in whirlpool bath.
What is the word for the water resistance level of the sunscreen?
Substantivity 40 = 2 x 20min water immersions in whirlpool 80 = 4 x 20 min water immerisions
What type of UVR does the SPF mostly measure protection against?
UVB, no easily reproducible endpoint for UVA radiation. There are human-based skin assays though
At want point does the percentage of UV blockage level off by sunscreen?
AT about SPF 30 (even SPF 15 is 93%). However, this is with optimal applications
What are the 4 UVB chemical blockers?
Octinoxate (octyl methoxycinnamate) Octisalate (octyl salicylate) Octocrylene Ensulizole (phenylbenzimidazole sulfonic acid)
What are the 4 UVA chemical blockers?
Oxybenzone
- Meradimate (methyl anthranilate) Avobenzone (Parsol 1789) Ecamsule (Mexoryl SX)*
What are the two physical blockers?
Titanium dioxide and Zinc oxide
At what age can infants start using sunscreen?
6 months of age
What daylight hours should be avoided?
10AM-4PM whenever possible
How long should sunscreen be applied before going out?
15 minutes before sun exposure
How often should you re-apply sunscreen with sweating or swimming?
Every 2 hrs
Which sunscreens should be used in patients w/ lupus, dermatomyositis, and other sun-sensitive conditions?
Physical blockers, these block UVB/A and visible light making them better for these patients.
