Sunlight and the skin

Question 1

What are the 3 main types of UV radiation?

Answer 1

UVA
UVB
UVC

Question 2

Which type of UVR is blocked by the ozone?

Answer 2

UVC

Question 3

Which type of UVR is blocked by window glass?

Answer 3

UVB

Question 4

What are the 6 skin phototypes?

Answer 4

I - Only burns

II - Burns, can tan

III - Tans, can burn

IV - Tans

V - Dark brown skin

VI - Black skin

Question 5

What determines a persons skin phototype?

Answer 5

Eumelanin:Phaeomelanin ratio

Question 6

What are some benefits of UVR exposure?

Answer 6

• Vitamin D synthesis
• Heat
• Vision
• Circadian rhythms
• Bactericidal and virucidal
• Therapeutic and diagnostic use

Question 7

What is involved in photodynamic therapy?

Answer 7

Application of porphyrin (Light sensitiser) in a cream, followed by irradiation with red light

Question 8

What are some uses of photodynamic therapy?

Answer 8

Superficial non-melanoma skin cancer and pre-cancers

Question 9

What is a possible application of far-UVC?

Answer 9

It may soon be used in social places to kill bacteria and viruses

Question 10

What are some risks of UVR exposure?

Answer 10

• Sunburn (Erythema)
• Eye damage (Conjunctivitis, Keratitis, Cataracts)
• Photo-ageing
• Skin cancer
• Photosensitivity disease
• Immunosuppression

Question 11

What are some presentations of photo-ageing?

Answer 11

• Solar elastosis
• Irregular pigmentation (E.g. Freckling, Lentigo)
• Telangiectasia and atrophy
• Roughness and dryness
• Deep wrinkling

Question 12

What causes solar elastosis?

Answer 12

degradation of elastin in the skin, resulting in increased wrinkling and yellow pigmentation of the skin due to build ups of elastin residue

Question 13

What types of UVR are emitted by sunbeds?

Answer 13

Mostly UVA, with very small levels of UVB

Question 14

What diseases can be caused by sun beds?

Answer 14

Melanoma and non-melanoma skin cancer (Classified as a carcinogen under the same category as tobacco)

Question 15

How does UVB cause DNA damage?

Answer 15

A photon of UVR is absorbed by the DNA in the nucleus of a keratinocyte, causing the formation of pyrimidine dimers and distortion of the DNA helix and interference with base pairing

Question 16

How does UVA cause DNA damage?

Answer 16

UVA causes indirect oxidative DNA damage and penetrates much more deeply into the skin

Question 17

What is xeroderma pigmentosa?

Answer 17

A condition caused by a mutation in the nucleotide excision repair (NER) mechanisms, preventing repair of damaged DNA, increasing the susceptibility to skin cancer

Question 18

How does UV exposure cause immunosuppression?

Answer 18

It results in the release of IL-10 from keratinocytes in the skin, therefore decreasing Langerhan’s cells response

Question 19

What are some methods of preventing photo-ageing?

Answer 19

• Avoid sun exposure between 11 and 3
• Cover up using hats and clothing
• Use sunscreen (At leats SPF 15)

Question 20

What are sunscreens?

Answer 20

Topical agents that reflect, absorb or scatter UV light

Question 21

What is SPF?

Answer 21

Sun protection factor

Question 22

How is SPF calculated?

Answer 22

This is calculated by the number of times greater the length of time a person can stay in the sun with vs without, before erythema occurs

For example, a person who’s skin would burn after 20 minutes in the sun, wearing SPF15, will take 300 minutes (5 hours) to burn when wearing sunscreen

Question 23

What are some factors that decrease efficiency of sunscreen?

Answer 23

Sweating
Swimming
Friction
Inadequate application