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Cutaneous Effects of Sunlight by Mind Map: Cutaneous Effects of Sunlight
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Cutaneous Effects of Sunlight

e.g., Oxybenzone


Action Spectrum

the wavelength that produces a  biologic effect

Absorption Spectrum

the wavelengths that are absorbed by a chemical.


The unit of measurement of sunburn

The minimum UVL exposure that produces a clearly marginated erythema in the irradiated site 24 hours after a single exposure

Units, UVA, J/cm2, UVB, mJ/cm2


Amount of UVB* Energy (Protected/Unprotected)

There is a popular misconception that SPF relates to time of solar exposure.

Photo-Toxic Reaction

Exaggerated reaction to UVR-induced activation of a phototoxic agent (i.e., Exacerbated Sunburn)

Non-immunologic Phenomenon, Reproducible in every individual, No prior sensitization required

Photo-Allergic Reaction

DTH (Type IV hypersensitivity reaction)

Only previously sensitized individuals develop a photo-allergy

Most Common Causes, Sunscreens (US), Especially benzophenone-3 (oxybenzone), NSAIDs (Germany, Austria and Switzerland)

Photo-sparing areas of the Head and Neck

Wilkinson’s triangle (behind the ears)

Nasolabial folds

Submandibular Neck

Contact dermatitis involves these areas




UV Hardening

A therapy used to improve tolerance for environmental  ultraviolet radiation (UVR) in photosensitive  disorders.

Skin Reactions to Sunlight


Acute and Subacute, Sunburn, Erythemogenicity: UVB = 1000 UVA, UVB is more erythemogenic (peaks at 300 nm), so erythema always precedes tanning, UVA induces tanning without noticeable erythema, UVA is significantly less erythemogenic than UVB, but more effective in producing a longer lasting tan, Erythema is due to vasodilation in papillary dermis, Mediators, Prostaglandins, may reduce erythema with NSAIDs, IL-6, TNF-alpha, CRP, Wavelengths, UVA, Begins during irradiation; more persistent; deeper red color, Fading in several days (within 48 to 120 h), UVB, Immediate Erythema (Starts within seconds then disappears), Delayed Erythema (Peaks in 12-24 hours), UVC, Very erythematous response and shorter in duration, Peaks at 5-8 hours; fades in hours to a day, Tanning, Immediate/Persistent Pigment Darkening, UVA, Existing Melanin, Photo-oxidative darkening and cellular re-distribution of already-present melanin within keratinocytes, Delayed Tanning (DT):, UVB, New Melanin Produciton, UVB induces delayed tanning which takes several days or longer to develop and requires activation of melanocytes., Result of increased number of melanocytes, melanogenesis, and increased transfer of melanosomes to keratinocytes, Develops in genetically susceptible individuals (i.e., not skin phototype I), Peak melanogenesis occurs at 290 nm (UVB), Peaks in 72 hours after exposure to mostly UVB light, Epidermal Hyperplasia, Due to UVB and UVC, but generally not UVA exposure, It adds to UVR protection, UVB induces both tanning and epidermal hyperplasia and produces protection factor of 3 as compared to UVA’s of 1.4, Histologically evident within days and persists for weeks, Immunologic Changes, Photo-Immunosuppression, in Th1 cytokine profile (IL-12 and IFN-gamma), Beneficial for Psoriasis, in the Th2 immunosuppressive profile (IL-4 and IL-10), May rarely exacerbate Atopic Dermatitis, Downregulation of DTH, Langerhans cells leave epidermis, UVB>UVC>>>UVA, Vitamin D3 Synthesis, Hormone (not a vitamin), Synthesis, UVB mediated process, 7-Dehydrocholesterol (7-DHC) + UVB > Cholecalciferol (Pre-Vitamin D) >25(OH)D hydroxylation(Liver) > 1,25 D (kidney), Previtamin D3 (pD3) undergoes thermal photo-isomerization to Lumisterol and Tachysterol (biologically inert photoproducts), which are interconverted in a chemical equilibrium, Only 10-20% of 7-DHC can be converted to pD3 at any given UVB exposure. This equilibrium is reached quickly, long before any risk of sunburn, and prolonged exposure to UVB will lead to more inactive photoproducts and increased UVR cancerogenesis., 25(OH)D, is the main circulating storage form and is measured in blood to determine the, Protects against the development of many chronic diseases and cancer, cardiovascular disease, multiple sclerosis, osteomalacia, osteoporosis, type 1 diabetes mellitus, rheumatoid arthritis, hypertension and depression, cancer (breast, pancreatic, colorectal, ovarian, prostate), Types, D2, Plant derived, Most widely used in supplements, and fortified milk, margarine, butter and cereals, Lesser Bioavailability, D3, Synthesized in the epidermis, Found in animal food sources, especially oily fish (herring, salmon, sardines), Only vitamin D + Calcium leads to decreased risk of hip fractures, and not vitamin D alone, Adequate Daily Intake is very controversial, Institute of Medicine : 0-12 months (400 iU), 1-70 (600 iU), 71+ (800 iU), Pregnancy/Lactation (600iU)

Chronic, Photo-aging, Important role of UVA, Conditions, Solar Elastosis, Solar Lentigo, Ephelides (Freckles), Poikiloderma of Civatte, Favre-Racouchot Syndrome, Colloid Millium, Erosive Pustular Dermatosis of the scalp, Multiple sterile pustules on a photo-damaged bald scalp and lower extremities of patients with atrophic skin and venous HTN, thought to be related to the cutaneous atrophy, Therapy, Topical (potent topical steroids and tacrolimus), PO (isotretinoin, ZnSO4, Nimesulide)


Photo-carcinogenesis, Molecular Genetics, DNA Damage, Direct (UVB), DNA photoproducts, thymine dimer, 6,4-photoproducts, covalently bound dimers, Indirect (UVA), 7,8-Dihydro-8-oxoguanosine (8-oxoG), DNA Damage via Singlet Oxygen species, Cellular chromophores are excited to produce singlet oxygen species, Nucleotide Excision Repair, if defective?, Cockayne Syndrome, Xeroderma Pigmentosum (A-G), Trichothiodystrophy, Tumor Supressor Genes, p53, UV Signature Mutation, Mnemonic: “CT Scan gives you SCC”, Not found in internal malignancies, C→T mutations, CC→TT tandem mutations, NMSCs are often associated with UV specific ("UV Signature Mutations") in the p53 gene, Melanoma has low incidence of these mutations, BCC, p53 is associated with aggressive growth BCC variants, 40% BCC have p53 mutation, 72% of these 40% bear the signature of UVL induciton, SCC, PTCH, See Nevoid BCC, Proto-Oncogene, BRAF, Mnemonic: “Melanoma ATe turkey BRAFo sandwich.”, Melanoma has T:A --> A:T mutations in BRAF gene., Oncogene, ras, Non-Melanoma Skin Cancer, Melanoma (N-ras), Nevoid Basal Cell Carcinoma, Inheritance, Autosomal Dominant, Defect, PTCH (9 q22–q31), A tumor suppressor gene, Transmembrane receptor for the Sonic hedgehog (shh) signaling protein, Expressed in hair follicule, Normal Function, Binds smoothened (SMO), Apoptosis, Binding of Sonic Hedgehog signaling protein, Apoptotic Signaling Cascade, Apoptosis, Pathogenesis, PTCH gene mutation (truncated protein), Gli-2, Bcl-2, Apoptosis, Melanoma and UVA Controversy, Epidemiological Observations, Melanoma Risk (Epidemiological Evidence), PUVA, Melanoma, Laboratory Observations, UVA does not cause melanoma in fish model, UVA, PUVA, SCC, Melanoma, UVA does not cause melanoma in fish model, UVB, UVB is the action spectrum for Melanoma development (the best supported evidence), Life-Style, Intermittent UVR Exposure, BCC, Chronic Exposure (Life Time UV Exposure Dose), SCC, Melanoma (especially Lentigo Maligna), Tanning Beds, Melanoma Risk (Epidemiological Evidence), Mainly UVA Radiation, Body Locations, Melanoma: more common on the Trunk in Men, and Lower Extremities in Women

Other Conditions, Idiopathic (Immunologic), Phototoxicity and Photoallergy, (Sunburn), Photosensitizing Medications, Antibiotics, Tetracyclines, Fluoroquinolones e.g. ciprofloxacin, Sulfonamides, NSAIDs, Ibuprofen, Naproxen, Ketoprofen, Celecoxib, Diuretics, Frusemide, Bumetanide, Hydrochlorothiazide, Retinoids, Isotretinoin, Acitretin, Hypoglycaemics, Sulfonylureas (e.g. glipizide, glyburide), Neuroleptics (anticonvulsants), Phenothiazines (e.g. chlorpromazine, fluphenazine), Thioxanthenes (e.g. chlorprothixene), PDT photosensitisers, 5-aminolevulinic acid, Methyl-5-aminolevulinic acid, Photofrin, Other drugs, Amiodarone, Diltiazem, Quinine, Quinidine, Hydroxychloroquine, Enalapril, Dapsone, Photosensitizing Topical Agents, Sunscreens, Benzophenones, Para-aminobenzoic acid (PABA), Cinnamates, Salicylates, Fragrances, Musk, 6-methylcoumarin, Miscellaneous, 5-Fluorouracil (oral and topical), Coal tar, Chemical-Induced, Phytophotodermatitis, Phototoxic reaction to a photosensitizing agent from a plant, UVA is the most common action spectrum, Plants contain Furocoumarins (Psoralens and Angelicins) as phototoxic agents, Most common plant families:, Rutaceae Family (Citrus Fruits), Lime, Rue, Apicaceae Family, Celery, Moraceae (the fig tree), Furocoumarins found in the sap of leaf and shoots, Not the fruit (figs), Fabaceae (Leguminose), Psoralea corylifolia has been used since 1400 BC to treat Vitiligo in India, St. John’s Wort, Screen (UVA1) Phototherapy patients, HIV patients receiving systemic hypericin as a potential antiretroviral therapy have developed a severe phototoxicity, Photo-Aggravated Dermatoses, Acne vulgaris, Atopic dermatitis, Bullous pemphigoid, Carcinoid syndrome, Cutaneous T-cell lymphoma, Dermatomyositis, Disseminated superficial actinic porokeratosis (DSAP), EM, Familial benign chronic pemphigus (Hailey–Hailey disease), Hartnup syndrome, Keratosis follicularis (Darier disease), Lichen planus, Lupus erythematosus, Pellagra, Pemphigus, including pemphigus foliaceus (erythematosus), PRP, Psoriasis, Reticular erythematous mucinosis (REM), Rosacea, Seborrheic dermatitis, Transient acantholytic dermatosis (Grover's disease), Viral infections (including herpes simplex), Metabolic, see Porphyrias, Nutritional, Pellagra, Genodermatoses, Phytophoto-Allergic Contact Dermatitis, A phototoallergic reaction have been described to ?, Parthenium hysterophorus


Skin Phototypes

Fitzpatrick, TB: Soleil et peau. J Med Esthétique 1975 2: 33–34

I, Always Burns, Never Tans

II, Usually Burns, Tans with Difficulty

III, Sometimes Mild Burn, Gradually Tans

IV, Rarely Burns, Tans with Ease

V, Very Rarely Burns, Tans Very Easily

VI, Never Burns, Tans Very Easily

Wavelengths (nm)

  Energy is directly proportional to the frequency and inversely so to the wavelength Becuse UVB and UVC are rapidly absorbed by DNA of the epidermal cells, they do not penetrate epidermis UVA (dermatoheliosis)and visible light (e.g., blue nevus) penetrate dermis and are absorbed by aromatic amino acids, collagen, elastin, and ground substance.


Visible (400-750), ROY-G-BV, Violet (400-450), Blue (450-495), Green (495-570), KTP, Nd:YAG, Yellow (570-590), PDL (e.g., LP-PDL 595 nm), Orange (590-620), Red (620-750)

UVA (320-400), UVA 1 (340-400), UVA 2 (320-340), Wood's Light (365)

UVB (290-320), Narrowband UVB (311-312), Excimer Laser (308), 290 nm (Peak Melanogenesis), 300 nm (Most Erythemogenic), 352 nm (Photo-testing and PUVA Peak Emission)

UVC (200-290), UV Light Source, Mercury Vapor Lamps (254)

Depth of photon skin penetration is directly proportional to wavelength

UVB, 2-5% UVB reaches the skin, Out of this, only 14% reaches melanocytes and lower epidermis

UVA, Less affected by environment (penetrates: Clouds and Glass), Up to 50% reach the depth of melanocytes and the dermal compartment, The total photon energy delivered into the lower epidermis and upper dermis (100 UVA > UVB)


UVA Facts, Causes photoallergic and phototoxic contact dermatitis, Photo-patch testing is done with UVA, If UVA-sensitive patient?, Phototesting is done with 0.5 x MED-A, see Photocancerogenesis, See Action Spectra

UVA Therapies, PUVA, Cancerogenicity, SCC (not BCC), Melanoma Controversy, No increased risk of melanoma according to Bolognia, Melanoma, Safe for HIV-infected psoriasis patients, Tar Smarts

Photopheresis, PO 8-MOP --> venous blood draw --> Photopheresis machine separates and exposes mononuclear cells (buffy coat) to 2 J/cm2 of UVA --> re-infusion, Induction of an immune response to malignant cells is postulated, Works better if, (CD4/CD8) < 10, Normal LDH, Indications, CTCL (especially erythrodermic CTLC), Chronic GVHD, Acute allograft rejection


UVB Facts, SPF is measured based on UVB, UVB erythema reaches a maximum in 6 to 24 hours, Most effective for?, Suppressing cutaneous immunity, UVL treatment modality for?, Psoriasis, Vitiligo, CTCL, Inducing neoplasia in mice

UVB Therapies, Excimer Laser (308 nm), Narrowband UVB (311-312 nm), The peak of NB-UVB spectrum = 10x the peak of BB-UVB curve, Significantly less erythemogenic (therefore less cancerogenic) than BB-UVB, Thus, more therapeutic UVB can be delivered before sunburn, No association between NB-UVB and NMSC, Side Effects, Broad Band, Short Term, Painful erythema resulting from overexposure is treated with topical corticosteroids, Erythema, Xerosis, Blistering and Pruritus, Recurrent herpes simplex viral infections, Long Term, Photoaging, Carcinogenesis, UVB << PUVA, Treatment, Painful Erythema, Topical Corticosteroids, Sever Cases, Systemic NSAIDs and corticosteroids, Narrowband, Longterm SE's yet to be determined


Arc Welders

Action Spectra

by Condition, PMLE, UVA, Drug-Induced Photosensitivity, UVA and/or UVB, CAD, UVB, Solar Urticaria, Visible Light, Photo-Contact Dermatitis, UVA, Hydroa Vacciniforme, UVA, Lupus Erythematosus, UVB, Xeroderma Pigmentosum, UVB

by UV Type, UVA, PMLE, Hydroa Vacciniforme, Photo-Contact Dermatitis, Drug-Induced Photosensitivity, UVB, CAD, Lupus Erythematosus, Xeroderma Pigmentosum, Visible Light, Solar Urticaria


SPF measures UVB coverage, SPF+ denotes UVA coverage, FDA uses 2 mg/cm2 of sunscreen in testing

The best UVA protection is provided by products that contain zinc oxide, avobenzone, and ecamsule, Titanium dioxide does not cover UVA spectrum completely

The best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, or rubbing/wiping.

People commonly apply only 1/2 to 1/4 of the amount recommended

One study indicates that the relation between SPF and sunscreen quantity follows exponential growth. Application of 1 mg cm−2 or 0·5 mg cm−2 makes the SPF fall as the square or fourth root, respectively, and 4 mg cm−2 results in an almost squared SPF. (Br. J. Dermatol., 156: 716–719.)


Used for the patients suspected of photosensitivity

Done on the unaffected and untanned skin of the gluteal area, lower back or ventral forearms.

6 test squares of increasing UV doses

MED, The dose of UVR that produces minimal erythema that completely fills the test square, Read 24 hours after exposure

Only the patients with possible solar urticaria are evaluated until 30 minutes after exposure