L15: Sunscreens Flashcards
What is the main electromagnetic wave concerned with skin damage from sunlight exposure?
UV light, specifically UV-A and UV-B
Which is the main cause of sunburn and skin cancer, UV-A or UV-B?
UV-B
Which penetrate deeper into the skin, UV-A or UV-B?
UV-A
Which does more damage to the skin, UV-A or UV-B?
UV-A
What are some of the natural protective mechanisms against ultraviolet light present in the stratum corneum?
- Scattering and reflection of UV radiation by corneocytes
- Endogenous body antioxidants (eg. carotenoids, urocanic acid and superoxide dismutase)
Epidermis absorbs radiation of what wavelength?
< 320nm
Which layer of the skin absorbs radiation wavelengths of > 320nm?
Dermis
How does tanned skin arise from exposure to ultraviolet rays?
UV rays are absorbed by melanin, causing it to oxidize and result in tanned skin.
This process is called delayed tanning or persistent pigment darkening
What is skin colour determined by?
- Mix of carotenoids
- Different types of melanin
- the way that melanin is packaged and distributed in melanosomes
What is the relationship between skin pigmentation and incidence of sun-induced skin cancers?
Inverse relationship
What causes albino phenotype?
Defective melanocytes, thus unable to produce melanin for photo-protection
What are the two types of albinos?
Constitutive and facultative
What is skin cancer caused by?
Long-term exposure to the sun and bad sunburns
What kind of eye damage can the sun do?
- Cataracts
- Photokeratitis
- Pterygium
- Cancer of the eye
What are the 3 main types of skin cancer?
- Basal cell carcinoma
- Squamous cell carcinoma
- Melanoma
Can exposure to sun cause allergies?
Yes
What are the two main types of sunscreens?
Organic and inorganic
What is the MOA of organic sunscreens?
Absorb UV radiation like melanin and transform it into heat
Organic sunscreens can offer sufficient protection with just one application throughout the day. True or False?
False. it must be frequently reapplied to maintain protection from the sun.
What is the MOA of inorganic sunscreens?
Reflect or scatter UV radiation, absorbing little energy
Inorganic sunscreens should be frequently reapplied to confer sufficient protection against the sun. True or False?
False. Their effect lasts longer and do not require frequent reapplication.
What are some examples of UVA organic sunscreens?
- Benzophenones
- Avobenzone
- Anthranilates
Salicylate is a type of UVB organic sunscreen. True or False?
True.
Cinnamate is a type of UVA inorganic sunscreen. True or False?
False. It is a UVB organic sunscreen
What are some examples of inorganic sunscreens?
- Titanium oxide
- Zinc oxide
What are the advantages of employing nanoparticles in sunscreens?
- Transparent
- Aggregation
What are some disadvantages of employing nanoparticles in sunscreens?
- May penetrate into the deeper layers of the skin; may confer side effects that are yet known
- Toxic to the environment (as it kills plankton)
What does Minimal Erythema Dose (MED) refer to?
Minimum UV radiation dose that produces clearly emarginated erythema in the irradiated site, given as a single exposure
TLDR: minimum UV radiation dose to cause sunburn
What is the formula for Sun Protection Factor?
MED of protected skin / MED of unprotected skin
or
Time to produce erythema on protected skin / Time to produce erythema on unprotected skin
What does an SPF of 6 mean?
It means that it takes 6 times longer for skin protected with this sunscreen to develop sunburn than normal
How much sunscreen should be applied?
Apply 2mg/cm^2 of sunscreen
For an average-sized person, this is equivalent to a shot glass
What are some disadvantages of water-resistant sunscreens?
- Water dissolves the oily sunscreen film by interacting with the emulsifier
- Rubbing removal
- Physical degradation
What kind of ingredients should after-sun products contain?
- Moisturizer
- Anti-inflammatory ingredients
- Cooling compounds: Menthol, camphor
- Antioxidants: Vit E, Vit C, carotenoids, coenzyme Q10
- Others: Extra virgin olive oil, Aloe, Shea butter
What are the protective measures against UV radiation?
- Avoid the sun
- Use sunscreens
- Wear a hat
- Cover up
- Wear sunglasses
- Avoid artificial tanning
What is the upper SPF limit?
50
Why is it not recommended for sunscreens to have SPF of > 30?
It offers little additional benefit and may unnecessarily expose users to dangerous levels of chemicals
What additional information should water-resistant or sweat-resistant sunscreens provide?
SPF for both before and after being exposed to water or sweat
Any tanning product that doesn’t contain a sunscreen would have to state on the label that the product does not contain a sunscreen. True or False?
True
