Sunscreens

Question 1

What is the percentage of UV light in sun rays?

Answer 1

6.1%

Question 2

Of that, what is the percentage of UV-B and UV-A?

Answer 2

UV-B: 0.5%

UV-A: 5.6%

Question 3

What is the main cause of sunburn and skin cancer?

Answer 3

UVB radiation; it does not penetrate the skin as deeply as UV-A but has more energy and therefore does more damage

Question 4

What does UV-A radiation cause?

Answer 4

Photoaging

Question 5

Name 3 natural UV protective mechanisms

Answer 5

1. Stratum Corneum -> UV is scattered & reflected by corneocytes
2. Melanin -> Dissipates UV as heat, undergoes oxidation which results in pigmentation upon UVA exposure
3. Body Antioxidants -> carotenoid pigments, urocanic acid, glutathione
   BUT protects minimally therefore need sunscreen

Question 6

What wavelength radiation gets absorbed into the epidermis and what wavelength into the dermis?

Answer 6

Epidermis: <320nm
Dermis: >320mm

Question 7

Is UVA or UVB more carcinogenic?

Answer 7

UVB because of its ability to damage DNA

UVA causes indirect DNA damage but mainly accelerates photoaging

Question 8

Why do albinos not have any photoprotection?

Answer 8

They have defective melanocytes -> no melanin

Question 9

What are the 3 main types of skin cancer?

Answer 9

1. Basal cell
2. Squamous cell
3. Melanoma

Question 10

How does basal cell carcinoma look like?

Answer 10

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

Question 11

How about squamous cell carcinoma?

Answer 11

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

Question 12

What about melanoma?

Answer 12

Most dangerous form of skin cancer -> can be fatal

Dark brown/black lump with irregular edges

Question 13

What is photokeratisis?

Answer 13

“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

Question 14

What is pterygium?

Answer 14

Growth of mucous membrane that covers the white part of eye, tends to recur
Caused by prolonged exposure to UV

Question 15

Where is a common location of basal cell carcinoma?

Answer 15

Eyelids

Question 16

Why does exposure to the sun cause bumps, hives, blisters etc. (allergies)?

Answer 16

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

Question 17

Difference between organic (chemical) and inorganic (physical) sunscreens?

Answer 17

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

Question 18

What are 3 UVA Organic sunscreen filters?

Answer 18

Absorb mainly in the 320-360nm range

1. Benzophenones
2. Avobenzone/Octocrylene (more stable)
3. Anthranilates

Question 19

What are 3 UVB Organic sunscreen filters?

Answer 19

Absorb mainly in the 290-320nm range

1. PABA derivatives
2. Salicylates
3. Cinnamates

Question 20

What are some inorganic sunscreen filters?

Answer 20

Titanium dioxide, zinc oxide

Question 21

Is there a problem with inorganic nanoparticles? If so, what?

Answer 21

Yes, penetration through skin is possible if nanoparticles are <13nm

Nanoparticle zinc is toxic to plankton

Question 22

What is MED?

Answer 22

Minimal Erythema Dose

min amt of UV rays to get a sunburn

Question 23

Formula of SPF?

Answer 23

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.)

Question 24

Is SPF 100 encouraged?

Answer 24

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

Question 25

Other than the magnitude of the SPF, what else is important?

Answer 25

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

Question 26

If a person rarely tans, should she apply sunscreen that is of a higher SPF or it doesn’t matter?

Answer 26

Yes, always burns easily -> SPF 30+

Rarely burns, tans -> SPF10-15

Question 27

Name 3 possible instances where water-resistant suncreens fail

Answer 27

1. Water dissolves in the oily sunscreen film by interacting with the emulsifier
2. Rubbing causes removal
3. Physical degradation -> leaving behind a film that lacks ingredients req to achieve the labelled SPF

Question 28

What are 3 ingredients that after sun products have?

Answer 28

1. Cooling compounds: methanol & camphor
2. Antioxidants: Vit E & C, carotenoids, coenzyme Q10
3. Others: Extra virgin olive oil, aloe, shea butter

Question 29

At what UV index should you avoid the sun?

Answer 29

If UV index above 3 / when shadow is shorter than you

Question 30

What does broad spectrum mean in sunscreens?

Answer 30

Protects against both UVA & UVB

Question 31

4 main FDA Guidance & ASEAN sunscreen labelling?

Answer 31

1. Upper SPF limit is around 50 bc anyth above 30 offers little additional benefits and may expose users to dangerous levels of chemicals
2. “Water/sweat resistant” products must list a SPF for both before and after being exposed to water or swear
3. Any tanning product that doesn’t contain sunscreen would have to state on label
4. No claim should be made that implies 100% UVA & UVB protection

Question 32

At what SPF should you not claim UV protection?

Answer 32

If less than SPF6