shevyatiwari's version from 2015-04-23 03:28


Question Answer
SPF is the dose of UVR required to produce 1 MED after application of 1mg/cm2 of the productF, 2mg/cm2
Broad spectrum = all UVA lengths coveredF, UVB too
water resistant is maintaining SPF after 40 minutes post water imemersionT, or 80 minutes
Chemical sunscreens are non aromatic conjugated with a carbonyl groupF, aromatic
Chemical sunscreens absorb high intensity UV -> excitation to a lower stateF, to a higher state - to infrared radiation, e.g. heat
Physical blockers reflect/scatter UVRT
Macro sized forms of physical blockers (aka inorganic particles) absorb UVR tooF, microsized
PABA is a common UVB sunscreenF - one of the first. But required alcoholic vehicle, stained clothing, associated with stinging and ACD
Padimate O is an ester derivative of PABAT
Padimate O is the most potent UVB absorberT
Octinoxate aka octyl methoxycinnamate are the least potent UVB absorbersF, second most potent after Padimate O
Octinoxate is the most commonly used sunscreen ingredientT
Octisalate aka octyl salicylate is a weak UVB absorberT
Octisalate can be used by itselfF, used to augment other sunscreens
Octocrylene is used in combination with other UV absorbers to achieve higher SPF formulations and photostabilityT
Ensulizole has the advantage of being water soluble and can be used in cosmetic moisturisersT
Ensulizole is hydrophilic unlike most other UVB sunscreensT
Oxybenzone is a UVB absorber onlyF, absorbs through UVAII. Is broad spectrum
Meradimate provides protection in UVAIIT, also a weak UVB filter
Meradimate is commonly usedF, less effective, not widely used
Avobenzone is a UVA absorber in UVAIIT - also provides protection through UVAI
Avobenzone is a stable productF, potential to degrade other sunscreens
Aveobenzone should be combined with octinoxate for stabilityF - degrades octinoxate. Should be combined with octocrylene or with non sunscreen ingredients such as diethylhexyl 2,6 napthalate
Ecamsule/Mexoryl SX has a broad spectrumT
Titanium dixide is less effective in UVA when particle sizes are reducedT
Titanium dixode is a broad spectrumT
Titanium dioxide is cosmetically accetableF.User may apply less 0> reduced SPF
Zinc Oxide has the added benefit to Titanium dioxide that it has more UVAI protectionT
Zinco Oxide is an appropriate sunscreen for those with PCT or other porphyriasF - doesn't work in the Soret band. These patients need opaque physical blockers
SPF 15 blocks 93.3% of UVR from penetrating skinT
Most individuals apply 1mg/cm2 of sunscreenT, about half whats reccommended
Higher the SPF, higher the UVAI protectionF, UVAII
A broad spectrum sunscreen has a critical wavelength of >/= 370nmT
Most broad spectrum sunscreens contain avobenzone or an inorganic particulate sunscreenT
The most common formulations are gelsF - emulsions.
Water is the best UV absorberF, oils
High SPF product can contain up to 20-40% oils -> heavy and greasy feelT
Sports sunscreens are less greasyT - dry lotions, less oily. Formulated using poylmeric film formers and less greasy silicone oils
Ultrasheel prodcuts contain gelsF, silica
Gels are easily removed in waterT
Gels do not cause stingingF
Those who have oily skin or acne may be more likely to use gelsT
Body hair or thinning scalp - favour creamsF, gels
Sprays can produce a less effective prodcutT
Sticks are thickened with waxes and petrolatumT
Sticks tend to contian hydrophilic sunscreensF, lipid soluble
Even without sunscreen, foundation can provide an SPF up to 4-5T
Most common S/E is photosensitivityF, subjective irritation
Erythema occurring immediately on contact may be ACDF, contact urticaria
Sunscreens are more likely to cause contact urticaria than other cosmeticsF
ACD is often due to the vehicle/additivesT
Photoallergic CD to sunscreens is one of the most common causes of photo allergic reactionsT
Sunscreen vehicle ingredients may be comedogenic but individual sunscreen oils are generally notT
Gels or sprays may be useful in those having acneT
Most important to be applied 3 hours before and after its day time maximumT
Sunscreen should be applied 15-30 minutes beforeT
Those with photosensitive dermatoses need particular protection in the UVB spectrumF, UVA esp UVA I
Sunscreen is not recommended for those <14 monthsF, 6 months
Those using sunscreen should take vit DT (600-800IU)
Those using DHA provide about 3-4SPFT
Contact folliculitis is characterised by the delayed onset of small follicular papules and pustulesF, rapid onset

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