DERM 10: Sunscreen and Sun-associated Disorders Flashcards
1
Q
How does skin change as we age?
A
- dryer
- thinner and more fragile – cell turnover slows, takes longer for cells to migrate from basal layer to skin surface
- more wrinkled with less elasticity
- reduced nail growth, sweat production, and sebaceous gland activity
- reduced blod flow (reduced vascularity), which slows wound healing
2
Q
What are the intrinsic factors to aging skin?
A
changes are determined by:
- genetics
- hormones
- independent of solar or environmental exposure
3
Q
What are the extrinsic factors to aging skin?
A
normal skin aging is exacerbated by radiation and environment:
- dyspigmentation (darker)
- premature and deep wrinkles
- telangiectasias
- decreased skin elasticity, and increased fragility
4
Q
What are some common skin defects/disorders in elderly?
A
(all fairly benign and do not require treatment):
- purpura
- solar lentigo
- seborrheic keratosis
- cherry angiomas
- xerosis
- pruritis
5
Q
Fitzpatrick Skin Types I and II
A
- most likely to show effects of photo-aging
- highest risk for development of skin cancer at early age
6
Q
Fitzpatrick Skin Types III and IV
A
- moderate risk of developing skin cancer
- will show effects of photo-aging (dermatoheliosis)
7
Q
Fitzpatrick Skin Types V and VI
A
- have very low risk of developing skin cancer
8
Q
What is ultraviolet radiation (UV)?
A
- electromagnetic waves, just beyond ‘purple’ end of visible light spectrum
- higher energy waves with shorter wavelength
9
Q
What is UVA?
A
- can cause DNA damage to skin cells by creating free radicals that harm cells
- main factor in skin tanning response
- long-term skin damage effects (wrinkles)
- some role in developing skin cancer
- classified by WHO as carcinogen
- longer wavelength allows deeper skin penetration,which affects dermis and contributes to skin aging and cancer
10
Q
What is UVB?
A
- direct damage to skin cells
- short-term immediate damage (sunburns)
- more direct link to skin cancers
- classified by WHO as carcinogen
- less penetrating than UVA (shorter wavelength) and most affect epidermis
11
Q
What is UVC?
A
usually does not make it past atmosphere
12
Q
Compare UVA vs. UVB in environmental exposure.
A
- UVB is higher risk than UVA
- UVB = sunburn
- UVA = dermatoheliosis
- UVB > UVA for cancer risk (especially melanoma)
13
Q
Compare UVA vs. UVB in therapeutic exposure.
A
- UVB therapy uses narrowly focused frequency ranges of UVB and dose is carefully calibrated to skin type – does not usually require photosensitizing agent like psoralen
- PUVA therapy with UVA is less focused and usually requires sensitizing agent like psoralen – combination of psoralen and UVA can cause more extensive DNA damage over time
- UVB therapy < PUVA therapy for cancer risk
14
Q
Why is UVA more linked to skin cancer with environmental exposure, but UVB is considered safer than UVA when used therapeutically?
A
- UVB rays carry more energy in environment than UVA rays
- dose of therapeutic UVB exposure is controlled and exposure time is limited
- UVA rays also penetrate deeper into skin than UVB
- by carefully controlling UVB exposure, can slow cell growth and reduce inflammation in targeted layer of skin more selectively
15
Q
What is photo-aging?
A
describes clinical changes to skin with chronic UV radiation exposure manifesting as:
- wrinkles deepen and forehead frown lines
- telangiectasias (spider veins), commonly on face
- ‘leathery’ skin
- solar lentigos (brown age spots)
- red scaly spots (pre-cancerous actinic keratosis)
- cutaneous malignancy (melanoma, squamous cell carcinoma, basal cell carcinoma)
16
Q
Describe the structure of the epidermis (outer layer).
A
- varies in thickness depending on anatomic site (palms vs. inner-elbow)
- made up of multiple layers of keratinocytes
- bottom layers generate new cells which work their way upwards
- no blood vessels
- melanocytes mixed in with cells of basal layer
17
Q
Describe the structure of the dermis (inner layer).
A
- supported by collagen and elastin
- contains blood vessels, nerve endings, sweat glands, etc
18
Q
What is the effect of UV radiation on the epidermis?
A
damaged keratinocytes need to be sloughed away and replaced
- basal keratinocyte layer creates new keratinocytes at accelerated rate
- requires shedding skin quickly = peeling
- in process of repairing skin, there can be errors in DNA replication, leading to uncontrolled cell duplication (basis of cancers)
melanocytes are activated to make melanin
- eumelanin (black/brown) vs. pheomelanin (red-yellow)
- coat basal keratinocytes in melanin pigment within few days
- creates a tan depending on how effective melanocytes are at this process
- equivalent SPF of ≤ 4 or less
- base-layer tan as protection is myth
19
Q
What is the effect of UV radiation on the dermis?
A
- UV rays that make it past ‘tanned’ keratinocytes need to be absorbed by proteins within dermis
- elastin fibres are more delicate – damaged quickly and turn blue under microscope
- collagen is replaced by homogenized elastin fibres, giving the ‘leathery’ look
- small vessels caught within this elastin goo remain more open and give the look of telangiectasias
- sun damaged skin is more difficult to repair surgically
20
Q
What is a sunburn?
A
UV-induced damage and hyperproliferation
- onset generally hours to days after exposure unless Fitzpatrick I, II, III
21
Q
What are the signs and symptoms of sunburns?
A
- subjective: painful and/or itchy skin
- objective: red, warm, possibly peeling skin in sun-exposed areas
22
Q
What is photosensitivity?
A
unusually severe reaction to solar energy
- either idiopathic or drug-related
- onset: more variable – sometimes minutes to hours after exposure
23
Q
What are the signs and symptoms of photosensitivity?
A
- similar presentation to sunburn
24
Q
What is basal cell carcinoma (BCC)?
A
- variable presentation
- rarely spread beyond original site
25
What is actinic keratosis (AK)?
- evidence of sustained solar exposure
- 5-10% turn into skin cancer
- if one is present, more are likely
- treatment to prevent progression
- surgery, cryotherapy, laser/chemical ablation
- topical fluorouracil (5-FU), imiquimod
26
What is squamous cell carcinoma (SCC)?
- accelerated growth of squamous cells
- largely curable
27
What is melanoma?
most dangerous skin cancer
- accelerated growth of melanocytes
- most likely to spread throughout body
28
What are the major risk factors for melanoma?
- personal and family history
- sun-sensitivity and excessive sun/UV exposure
- baseline risk: 3% in fair-skinned individuals, 0.1-0.5% in darker skinned individuals
- single blistering sunburn before age 20 increases risk of developing melanoma later in life
- one bad sunburn before age 18 increases risk of developing melanoma by 2x
29
What does sunblock do?
scatter/reflect UV radiation
30
What ingredients does sunblock contain?
certain inorganic ingredients – zinc oxide, titanium oxide
31
What does sunscreen do?
absorb and release UV radiation
- absorb UV radiation and release it as heat, vibration, or lower frequency light – aromatic molecules conjugated with carbonyl groups, octyl methoxycinnamate, oxybenzone, avobenzone, etc.
- released heat is generally harmless but can be problematic for specific individuals predisposed to hyperpigmentation
32
What ingredients does sunscreen contain?
certain organic (chemistry) ingredients
33
What is sun protective factor (SPF)?
measure of how long sunscreen remains effective on skin
- refers only to UVB protection, not UVA
34
What is the effectiveness of sunscreen on skin based on?
time to burn when unprotected
- ratio between unprotected and protected
- someone who burns within 10 minutes unprotected will burn after 150 minutes when using SPF 15 if reapplied as directed and isn’t washed/wiped off
35
Is there a benefit to SPF sunscreens over 40?
- no immediate benefit – immediate UV blocking ability of SPF 60 is no better than 40 or 50
- in sweat and water-free situation, SPF 60 should last longer
36
What are the different regulations for sunscreen labels?
- UVA/UVB coverage can be claimed if there is anywhere from 30-100% UVA coverage compared to UVB
- broad-spectrum means UVA coverage as well as UVB
- SPF alone usually refers to UVB coverage, not UVA
- SPF values greater than 50 are to be declared as SPF 50+
37
What are the types of endorsements on sunscreen labels?
CDA endorsements recognizes sunscreen products that meet a standard that provides effective sun protection, and requires:
- SPF 30 and above
- low irritation potential
- minimally perfumed or non-perfumed
- non-comedogenic
38
What is degradation?
organic ingredients become unstable and become inactive, and effective SPF decreases
- sunscreens ‘catching’ radiation change their structure and use up their potential to convert radiation into heat
- storing sunscreen in hot environment can destroy it – external heat can also use up potential
39
What is dissipation?
removal of protective molecules from skin by activity and moisture – sweating, swimming, wiping, scratching
40
What do stabilizers do?
many sunscreen developers have tried to find ways to stabilize sunscreens
- particularly important for organic ingredient avobenzone, which has broadest spectrum, but least stability
- prolong duration of advertised SPF factor, but does not stop dissipation
41
How should sunscreen be applied?
- needs to be slathered – SPF rating depends on thick coating of sunscreen
- needs to be applied 15-30 minutes prior to exposure
- only way to provide consistent protection is to reapply at least every 2 hours and immediately after swimming or washing
- water-resistant sunscreen is designed to stay on longer in water, but still needs frequent reapplication every 40-80 minutes while swimming
42
Does sunblock dissipate or degrade?
- less likely to degrade or dissipate, but still possible
- easier to see dissipation – but highly visible when used
43
What are the recommendations for pediatric sun protection for infants and children < 6 months?
- preference for inorganic over organic products – inorganic has less potential for absorption, safety of organic products unknown but also no evidence of risk
- physical barriers are most effective and most important
44
What are the recommendations for pediatric sun protection for children > 6 months?
- should follow same advice as adults
- will need more reminding and supervision with regard to reapplication
45
What are the recommendations for sun protection if pregnant and breastfeeding?
- systemic absorption of sunscreens is very minimal
- sunscreen used by nursing mother can be transferred to infant
46
How to Help Patients Select Sun Protection
- SPF of 30 or greater
- ‘broad-spectrum’
- should have DIN (Drug Information Number) in Canada
- ensure efficacy: check ingredients to ensure UVA/UVB coverage if not endorsed, check efficacy statements, choose water-resistant or sweat-resistant formulations
- choose an appropriate form – cream, lotion, spray
47
What are some counselling points when teaching individuals how to use sun care products?
- application: 20 minutes before exposure, reapply every 2 hours/after swimming/more if sweating, use more than you think
- still avoid sun
- do not inhale sprays: cover eyes and mouth and move away after, rub product in, careful not to miss areas or spray from too far away (10-15 cm)
- do not forget lips
- store sunscreen in cool and dark place – in cooler with drinks, not in hot car
- sunscreen before bug-spray
48
What are some examples of sun-protective clothing?
- UPF (ultraviolet protection factor)
- shirt with UPF 50 allows 1/50th of UV radiation through to skin
- standard t-shirt offers approximate UPF of 15
- consistent protection all day
49
What are some external physical barriers to block UV radiation?
- umbrella blocks about 70% of UV radiation but not reflected radiation
- single tree can block 2-50% of UV radiation
- forest can block between 2-100% of radiation
50
What is photosensitivity?
idiopathic
- most common is polymorphous light eruption (PMLE)
- sometimes know as ‘sun allergy’
- pruritic rash in sun exposed areas hours to days after exposure and may include hives or pin-prick papules
- often hereditary
51
What is phototoxicity?
drug-related
- occurs when photoreactive chemicals are activated by solar energy and transformed into products cytotoxic against skin cells, either when unstable species from excited state directly react with endogenous molecules, or when endogenous molecules react with secondary photoproducts
- present as exaggerated sunburn and restricted to sun-exposed skin – worse in area of drug application if topical
- minutes to hours after exposure
- usually a reaction between agent and UVA
52
What are some common drugs that result in phototoxicity?
- antibiotics (tetracyclines, sulfonamides, fluoroquinolones)
- metformin
- NSAIDS
- tar compounds
- HCTZ
- amiodarone
- St. John’s Wort
53
What are some photosensitivty/phototoxicity inducing agents?
plants
- giant hogweed
- cow parsnip
- lemons and limes
- celery
54
What is photoallergy?
rare reaction that can occur when body mounts immune response to UV modified allergen (delayed onset = 24-48 hours)
- looks more like contact dermatitis
55
What topical products can cause photoallergy?
- sunscreens
- NSAIDS
- fragrances
- antimicrobial agents (chlorhexidine)
56
What systemic products can cause photoallergy?
- quinine
- sulfonamide antibiotics
- piroxicam
- quinidine
- quinolones
57
What is the treatment for sunburns?
- treatment is generally supportive – damage is already done
- moisturizers can limit peeling
- cool compresses and cool baths can limit heat-related tissue damage – avoid ice
- oral NSAID/acetaminophen for pain
- topical diclofenac creams for pain and inflammation
- insufficient evidence for aloe vera, but anecdotal evidence of effect with minimal adverse reactions
- some products with topical anesthetics are designed to reduce pain/stinging: can be a source of contact allergy, topical anesthetics (lidocaine, bupivacaine) can result in methemoglobinemia if applied to large areas
- avoid further UV damage
58
What is the treatment for photosensitivity and photoallergy?
- treat like sunburn
- remove offending agent
- avoid treatments that may result in contact-allergy (anesthetics)
- photoallergy may respond to topical or systemic corticosteroids
- potential role for antihistamines for idiopathic sun allergy – minimal evidence
