Sunscreens Flashcards
What is the percentage of UV light in sun rays?
6.1%
Of that, what is the percentage of UV-B and UV-A?
UV-B: 0.5%
UV-A: 5.6%
What is the main cause of sunburn and skin cancer?
UVB radiation; it does not penetrate the skin as deeply as UV-A but has more energy and therefore does more damage
What does UV-A radiation cause?
Photoaging
Name 3 natural UV protective mechanisms
- Stratum Corneum -> UV is scattered & reflected by corneocytes
- Melanin -> Dissipates UV as heat, undergoes oxidation which results in pigmentation upon UVA exposure
- Body Antioxidants -> carotenoid pigments, urocanic acid, glutathione
BUT protects minimally therefore need sunscreen
What wavelength radiation gets absorbed into the epidermis and what wavelength into the dermis?
Epidermis: <320nm
Dermis: >320mm
Is UVA or UVB more carcinogenic?
UVB because of its ability to damage DNA
UVA causes indirect DNA damage but mainly accelerates photoaging
Why do albinos not have any photoprotection?
They have defective melanocytes -> no melanin
What are the 3 main types of skin cancer?
- Basal cell
- Squamous cell
- Melanoma
How does basal cell carcinoma look like?
Appears as a small, shiny, fleshy nodule on exposed parts of body
Grows slowly and rarely spreads to other parts of the body
High cure rate if treated early
How about squamous cell carcinoma?
Develops on face, ears, lips & mouth
Begins as a red scaly patch
Left untreated, it can spread to other areas and be fatal but if treated early can be cured
What about melanoma?
Most dangerous form of skin cancer -> can be fatal
Dark brown/black lump with irregular edges
What is photokeratisis?
“Sunburn” on the eye
Results from exposure in highly reflective environments
Appears a few hours after exposure and usually disappears in 2 days but very painful
What is pterygium?
Growth of mucous membrane that covers the white part of eye, tends to recur
Caused by prolonged exposure to UV
Where is a common location of basal cell carcinoma?
Eyelids
Why does exposure to the sun cause bumps, hives, blisters etc. (allergies)?
UV rays makes the immune system weaker esp so if done in conjunction with meds/vaccine
Diseases such as cold sores, chicken pox etc can become worse with sun exposure
Difference between organic (chemical) and inorganic (physical) sunscreens?
Organic: Absorbs UV radiation like melanin & transform it into heat, must be frequently reapplied
Inorganic: Reflect or scatter UV radiation, absorbing little energy, last longer
What are 3 UVA Organic sunscreen filters?
Absorb mainly in the 320-360nm range
- Benzophenones
- Avobenzone/Octocrylene (more stable)
- Anthranilates
What are 3 UVB Organic sunscreen filters?
Absorb mainly in the 290-320nm range
- PABA derivatives
- Salicylates
- Cinnamates
What are some inorganic sunscreen filters?
Titanium dioxide, zinc oxide
Is there a problem with inorganic nanoparticles? If so, what?
Yes, penetration through skin is possible if nanoparticles are <13nm
Nanoparticle zinc is toxic to plankton
What is MED?
Minimal Erythema Dose
min amt of UV rays to get a sunburn
Formula of SPF?
MED of protected skin / MED of unprotected skin
higher the SPF, the more effective preventing sunburn
If it takes 60 mins to get an erythema, sunscreen with SPF 6 will allow stay in the sun 6 times longer before getting sunburn (but doesn’t take into account perspiration etc.)
Is SPF 100 encouraged?
No, gives consumer the perception that its better than e.g. SPF50 when they have similar efficacy (SPF30 alr gives 97% protection) -> misleading conception that don’t need to re apply
SPF 100 = more ingredients = more risk of allergies
Other than the magnitude of the SPF, what else is important?
The amount applied onto the skin
FDA recommendation: 2mg/cm^2 = a full shot glass
If you apply half dose of the required sunscreen, you have protection equiv to only sq root of the SPF
e.g. sqrt30 = 5.5 SPF
If a person rarely tans, should she apply sunscreen that is of a higher SPF or it doesn’t matter?
Yes, always burns easily -> SPF 30+
Rarely burns, tans -> SPF10-15
Name 3 possible instances where water-resistant suncreens fail
- Water dissolves in the oily sunscreen film by interacting with the emulsifier
- Rubbing causes removal
- Physical degradation -> leaving behind a film that lacks ingredients req to achieve the labelled SPF
What are 3 ingredients that after sun products have?
- Cooling compounds: methanol & camphor
- Antioxidants: Vit E & C, carotenoids, coenzyme Q10
- Others: Extra virgin olive oil, aloe, shea butter
At what UV index should you avoid the sun?
If UV index above 3 / when shadow is shorter than you
What does broad spectrum mean in sunscreens?
Protects against both UVA & UVB
4 main FDA Guidance & ASEAN sunscreen labelling?
- Upper SPF limit is around 50 bc anyth above 30 offers little additional benefits and may expose users to dangerous levels of chemicals
- “Water/sweat resistant” products must list a SPF for both before and after being exposed to water or swear
- Any tanning product that doesn’t contain sunscreen would have to state on label
- No claim should be made that implies 100% UVA & UVB protection
At what SPF should you not claim UV protection?
If less than SPF6
