Page 177 - TNFlipTest

Toronto Notes 2019
Miscellaneous Lesions
Dermatology D43
Wounds and Ulcers
• seePlasticSurgery,PL8,PL16
Sunscreens and Preventative Therapy
Sunburn (Solar Erythema)
• erythema2-6hpostUVexposureoftenassociatedwithedema,painandblisteringwithsubsequent desquamation of the dermis, and hyperpigmentation
• chronic UVA and UVB exposure leads to photoaging, immunosuppression, photocarcinogenesis
• prevention:avoidpeakUVR(10am-4pm),wearappropriateclothing,wide-brimmedhat,sunglasses,
and broad-spectrum sunscreen
• clothingwithUVprotectionexpressedasUVprotectionfactor(UPF)isanalogoustoSPFofsunscreen
Sunscreens
• underidealconditionsanSPFof10meansthatapersonwhonormallyburnsin20minwillburnin 200 min following the application of the sunscreen
• topicalchemical:absorbsUVlight
■ requires application at least 15-30 min prior to exposure, should be reapplied every 2 h (more often
if sweating, swimming)
■ UVB absorbers: PABA, salicylates, cinnamates, benzylidene camphor derivatives
■ UVA absorbers: benzophenones, anthranilates, dibenzoylmethanes, benzylidene camphor
derivatives
• topicalphysical:reflectsandscattersUVlight
■ titanium dioxide, zinc oxide, kaolin, talc, ferric chloride, and melanin
■ all are effective against the UVA and UVB spectrum
■ less risk of sensitization than chemical sunscreens and waterproof, but may cause folliculitis or
miliaria
• somesunscreeningredientsmaycausecontactorphotocontactallergicreactions,butareuncommon
Management
• sunburn:ifsignificantblisteringpresent,considertreatmentinhospital;otherwise,symptomatic treatment (cool wet compresses, oral anti-inflammatory, topical corticosteroids)
• antioxidants,bothoralandtopicalarebeingstudiedfortheirabilitiestoprotecttheskin;topicalagents are limited by their ability to penetrate the skin
Skin Phototypes (Fitzpatrick)
Topical Steroids
Table 25. Potency Ranking of Topical Steroids
Phototype Colour of Skin
I White
II White
III White
IV Pale brown V Brown
VI Dark brown
or black
SPF = burn time with cream/burn time without cream
UV Radiation
UVA (320-400 nm): Aging
• Penetrates skin more effectively than UVB or UVC
• Responsible for tanning, burning, wrinkling, photoallergy, and premature skin aging
• Penetrates clouds, glass and is reflected off water, snow, and cement
UVB (290-320 nm): Burning
• Absorbed by the outer dermis
• Is mainly responsible for burning and
premature skin aging
• Primarily responsible for BCC, SCC
• Does not penetrate glass and is
substantially absorbed by ozone
UVC (200-290 nm)
• Is filtered by ozone layer
Body Site:
Relative Percutaneous Absorption
Forearm 1.0
Plantar foot 0.14
Palm 0.83
Back 1.7
Scalp 3.7
Forehead 6.0
Cheeks 13.0
Scrotum 42.0
Calculation of strength of steroid compared to hydrocortisone on forearm: relative strength of steroid x relative percutaneous absorption
Side Effects of Topical Steroids
• Local: atrophy, perioral dermatitis, steroid acne, rosacea, contact dermatitis, tachyphylaxis (tolerance), telangectasis, striae, hypertrichosis, hypopigmentation
• Systemic: suppression of HPA axis
Skin’s Response to Sun Exposure (without SPF protection)
Always burns, never tans
Always burns, little tan Slight burn, slow tan Slight burn, faster tan Rarely burns, dark tan Never burns, dark tan
Relative Potency
Weak Moderate
Potent Very Potent
Extremely Potent
Relative Strength
x1 x3
x6 x9
x12
Generic Names
hydrocortisone – 2.5% (1% available over-the-counter)
hydrocortisone 17-valerate – 0.2%
desonide
mometasone furoate
betamethasone – 0.1% 17-valerate – 0.1% amcinonide
betamethasone dipropionate – 0.05% fluocinonide – 0.05% halcinonide
clobetasol propionate – 0.05% (most potent)
betamethasone
dipropionate ointment halobetasol propionate – 0.05%
Trade Names
Emo Cort®
Westcort®
Tridesilon® Elocom®
Betnovate® Celestoderm – V® Cyclocort®
Diprosone®
Lidex, Topsyn gel® Lyderm®
Halog®
Dermovate® Diprolene® Ultravate®
Usage
Intertriginous areas, children, face, thin skin
Arm, leg, trunk
Body
Palms and soles
Palms and soles