2913201
Description
Flashcards by jenny schneider, updated more than 1 year ago
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Created by jenny schneider
over 9 years ago
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| Question | Answer |
| What are the three types of UV? | UVA, UVB, UVC |
| Which UV type is mainly responsible for sunburn? | UVB |
| True or False: UV reaching earth surface is mainly UVA (95%) and 5% UVB | True |
| Which type of UV penetrates further in to the skin- UVA or UVB? | UVA |
| How do sunscreens work? | Sunscreens work by absorbing, scattering and reflecting UV light |
| Which of the following are mainly UVB absorbers? PABA, octyl salicylate, methoxycinnamate, anthranilates | All except anthranilates which are UVA absorbers |
| What test is used to measure UVB effectiveness of sunscreen? | SPF |
| True or False: SPF testing is an in vivo test measuring protection against sunburn | True |
| Briefly describe how SPF is determined | in vivo test where ratio of ability of person to run with sunscreen is measured relative to ability to burn without sunscreen |
| True or False: If a person burns in 10 minutes without sunscreen and 150minutes with sunscreen, the SPF is 15 | True |
| Which of the following test are used to rate UVA protection: Boots star rating system Critical wavelength method Persistent Pigment Darkening test (UVA-PF) SPF | All except SPF- there are multiple tests- no international standard |
| Which of the following is NOT a sunscreen? octyl salicylate benzyl salicylate methyl salicylate Pamidate A octyl methoxycinnamate | methyl salicylate is NOT a sunscreen agent |
| If a sunscreen product has an SPF of 50 does it offer twice as much protection as an SPF25 product? | No, Look at plot in notes for percent protection versus SPF and note that it is not a linear plot |
| What are drawbacks of oil sunscreen formulations? | rapid and easy spreadability means very thin film (not as effective) can feel greasy higher cost to produce may have stability issues with some packaging |
| What type of ingredients (besides sunscreen agents) are you likely to find in an emulsion sunscreen? | oil, water, emulsifier, film formers, emollients (to help dissolve sunscreens and good feel), sensory enhancers (silicones) |
| What are some approaches used to make water resistant formulation? | w/o emulsion oil formulation optimise water resistance for o/w emulsions (most popular) by: minimising level of hydrophilic emulsifiers, using film formers, using polymeric emulsifiers |
| what factors affect the performance of a sunscreen? | blend of sunscreen agents used formulation uniform distribution on skin ensuring as thick a layer as possible |
| Why are levelling agents sometimes used in sunscreens? | we need a uniform and thick layer on skin for maximum effect. the best levelling agents show dilettante rheology and so resist flow when spreading on skin, enabling thicker layer |
| What were two safety concerns that have been raised about sunscreens? | concerns about oestrogenic effect of some sunscreen ingredients but these have been shown to be very weak and unlikely to occur concerns about nanoparticle formulations and penetration in to body- evidence from TGA shows little evidence that this is a problem |
| What are two inorganic metal oxides used as sunscreen agents? | zinc oxide titanium dioxide |
| True or False: titanium dioxide and zinc oxide particles will often try and re-aggregate in formulation, so particles are coated with agents such as silicon to reduce re-aggregation | True |
| True or False: particle size of the inorganic metal oxides (ZnO and TiO2) will affect the UV absorption produced | True |
| Which of the following statements are true? sunscreen agents may absorb UV and be degraded sunscreen agents are commonly used in combinations to produce desired spectrum of activity film formers are used in formulations to produce a uniform film and help with water resistance octocrylene is commonly combined with avobenzone to reduce instability of avobenzone | all statements are correct |
| Larger particle size of Zinc oxide and titanium dioxide lead to white appearance on skin, reducing particle size reduces this white appearance | True |
| How should you counsel patient on applying sunscreen | Use appropriate amount (need uniform and thick layer on skin) apply 20-30min before going out in sun (allows film to form) reapply every two hours |
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