Sunscreens Flashcards
(26 cards)
What are the divisions of Solar Ultra Violet Radiation?
- UVC (200-290nm)
- UVB (290-320nm)
- UVA (320-400nm)
- What categories of UV radiation reach the Earths surface?
- What happens to the other category?
- UVA and UVB reach the Earth’s Surface
- UVC is absorbed by the Ozone layer
- Can be generated by artificial sources such as arc welders
What are the biologic effects of UV radiation on the skin of UVA and UVB?
- UVA penetrates very deeply, when it gets there - affects DNA
- UVB most dangerous but doesn’t penetrate very far
UVB Radiation
- UVB constitutes __________ of all UV radiation that reaches the earth’s surface
- What does the shorter wavelength allow it to do?
- What can this lead to?
- UVB constitutes less than 10% of all UV Radiation that reaches the earth’s surface
- The shorter wavelength penetrates the epidermal layers of the skin
- This can lead to:
- Erythema (sunburn)
- Skin cancer
- Eye damage
- Skin ageing
- Immune suppression
UVA Radiation
- UVA radiation leads to the release and _____ of what?
- What does this create?
- What does UVA also lead to?
- UVA radiation leads to the release and oxidation of melanin from the melanocytes which creates a tan colour in the skin
- UVA also leads to skin cancer, ageing, immunosuppression
Human Skin and UVA transmission
- Untanned fair-skinned individuals
- Dark skin
- Untanned fair-skinned individuals
- 50%
- Dark skin
- 30-35%
- What is Skin Cancer?
- What is it Characterised by?
- Caused by?
- A disease of the body’s skin cells
- Characterised by the abnormal growth of skin cells
- Caused mainly by cumulative exposure to UVR from the sun
TRUE or FALSE
Do clouds block UV radiation?
- False
- A thin layer of clouds can let up to 80% of UV rays through
- A thick layer of cloud cover can block most but not all UV rays
TRUE or FALSE
A tan is healthy?
- False
- Sign that your skin has been damaged and has attempted to protect itself
- Skin produces a dark-coloured pigment, melanin, as a shield against further damage from UV radiation
TRUE or FALSE
Clothes block UV radiation
- Partially true
- A white, dry cotton shirt provides less protection than sunscreen with SPF 15
- Fabric that allows light through also allows UV rays through
- Wet clothing allows 50% transmission of UV radiation
TRUE or FALSE
Water doesn’t reflect UV radiation
- False, water does reflect UV (<10%)
- Snow reflects 80% of UV radiation
TRUE or FALSE
People with darker skin don’t get skin cancer
- False
- They’re at risk for skin cancer and most frequently at risk for melanoma
Sunscreens Actives Overview
What are the atoms involved in Organic Ingredients and Inorganic Ingredients?
- Organic Ingredients:
- Carbon, hydrogen, oxygen, nitrogen
- Inorganic Ingredients:
- Zinc, titanium, oxygen
Sunscreens Actives Overview
What is the Structure of Organic Ingredients and Inorganic Ingredients?
- Organic Ingredients:
- Individual Molecule
- Inorganic Ingredients:
- Clusters of Various Size
Sunscreens Actives Overview
What is the UV Blocking of Organic Ingredients and Inorganic Ingredients?
- Organic Ingredients
- Absorb specific bands of UV light
- Inorganic Ingredients
- Absorb all UV with λ < critical value
Sunscreens Actives Overview
What is the Appearance of Organic Ingredients and Inorganic Ingredients?
- Organic Ingredients
- Clear
- Inorganic Ingredients
- Large clusters = white
- Small clusters = clear
What is the mechanism of UV absorption with Organic Ingredients?
- Molecules capture energy from the sun’s UV rays
- The energy give the molecule thermal motion (vibrations and rotations)
- The energy is re-emitted as harmless long wave IR
What is the Absorption Range of Organic Ingredients?
- Organic molecules only absorb UV rays whose energy matches the difference between the molecule’s energy levels
- Using more than one kind of ingredient (molecule) gives broader protection
Is benzophenone-3 safe?
- When used as UV-filter at levels up to 6% in cosmetic sunscreen products and up to 0.5% in all types of cosmetic products, does not pose a risk to the health of the consumer, apart from its contact allergenic and photoallergenic potential
Is 4-MBC and OMC safe?
- Did not exert oestrogen like effects and estimated that currently approved sunscreens would need to be 100 000 times more potent before they showed any hormonal effect
Why do Zinc Oxide and Titanium Dioxide appear white on the skin?
- Clusters of molecules are large and therefore can scatter light in many different directions
- Maximum scattering occurs for wavelengths twice as large as the cluster (visible light)
- When reflected visible light of all colours reaches our eyes, the sunscreen appears white
- This is very different from what happens when sunlight is reflected off our skin directly
- Green/blue rays absorbed
- Red/brown/yellow rays reflected
How can a formulator overcome the whitening of the skin caused by light scattering?
By the use of nanoparticles of zinc oxide and titanium dioxide
Why is the use of nanomaterials in sunscreens controversial?
- Nanoparticles may penetrate beyond the dead cells of the stratum corneum into the living cells of the dermis causing cellular damage or accumulate in organs remote from application site - if they don’t penetrate the skin, there are not detrimental health implications from topical application of sunscreen containing these particles
- Currently, no in vivo evidence the indicate possible toxicity of nanoparticulate TiO2 or ZnO in people using sunscreens
Where do you get Vitamin D from?
- Around 80-90% of Vitamin D is made in the skin from exposure to the sun’s ultraviolet (UV) radiation
- It’s difficult to get enough vitamin D from diet alone
