chapter 12 sunscreen products Flashcards
types of UV light (and wavelengths)
● far UV (100-200nm) - highest energy
● UVC (200-290nm)
● UVB (290-320)
● UVA (320-400nm) - lowest energy, penetrates deepest into skin
why is UVC not that harmful to humans
> 99% absorbed by ozone layer and so it doesnt rly reach us
concerns of UVB rays (1+3)
SHORT TERM IMPACTS: penetrates stratum corneum
● primary initiator of sunburn
● causes premature skin ageing
● causes certain skin cancers
benefits of UVB rays (2)
● triggers vitamin D synthesis
● triggers generation of melanin (suntan)
concerns of UVA rays
LONG TERM IMPACTS
● 30-50% reaches dermis: absorbed by collagen and disrupts elastin bonds (ageing!!)
● immediate and delayed skin colouration and pigmentation
● contributes 15% to sunburn (overexposure)
concerns of UVA rays
LONG TERM IMPACTS
● 30-50% reaches dermis: absorbed by collagen and disrupts elastin bonds (ageing!!)
● immediate and delayed skin colouration and pigmentation
● contributes 15% to sunburn (overexposure)
effects of sunburn (6)
- tanning (injured pigment cells)
- premature wrinkling
- skin cancer
- eye damage eg. cataracts
- allergies to sun (bumps, hives, blisters, red blotchy areas)
- immune system suppression and diseases eg. herpes simplex, chicken pox, lupus, certain genetic problems
define minimal erythema doe (MED)
minimum UV radiation dose required to show the first sign of burning/erythema/reddening
calculate SPF
exposure time to produce redness on protected skin/unprotected skin
which skin types are SPF studies conduct on and why
type I and II (greatest risk of sun damage)
easily burns, minimal to no tan
function of sunscreen products and how is it accomplished
absorb/scatter/reflect solar UV
accomplished by
1. UV filter
2. film forming vehicle
“water resistant” vs “very water resistant”
“water resistant”: retains SPF after 40 min of activity in water
“very water resistant”: retains after 80 min
must provide direction on when to reapply
3 errors in sunscreen application
- not enough applied (rec. 2mg/cm2)
- did not reapply every 2h (even if water resistant)
- skipped some areas of skin eg. lips, nose, ear, eyelids
organic filters vs inorganic filters
● organic filters absorb UV rays and excite them to a higher energy state, converting UV energy to other energy forms like heat or light (fluorescence/phosphorescence)
● inorganic filters are BARRIERS: reflect/scatter broad spectrum, usu safer, but has white cast
UVA chemical absorbers
● oxybenzone/benzophenone derivatives
● anthranilates
