Photosensitivity PDF

Photosensitivity Incidence, Prevalence, and Epidemiology of Ultraviolet Radiation Exposure Understanding the impact of UVR on health  Changing Lifestyles and Increased UV Exposure  Increasing outdoor activities and recreational tanning.  Longer life spans and s...

Photosensitivity Incidence, Prevalence, and Epidemiology of Ultraviolet Radiation Exposure Understanding the impact of UVR on health  Changing Lifestyles and Increased UV Exposure  Increasing outdoor activities and recreational tanning.  Longer life spans and seasonal shifts to sun-rich areas (Sunbelt).  Emphasis on vitamin D deficiency and sun exposure.  Result: Increased human exposure to sunlight. Sunlight as a Causative Factor in Skin Diseases  Epidemiologic evidence links UVR exposure to various skin diseases.  Public attitudes toward tanning and sun exposure are gradually changing.  Skin cancer is the most common yet preventable cancer.  Skin Cancer: The Role of UVR  Skin Cancer Types:  Squamous Cell Carcinoma (SCC)  Basal Cell Carcinoma (BCC)  These account for over 50% of malignancies in the U.S.  SCC and BCC are closely linked to UVR exposure.  Melanoma: Rising Incidence Rates  Melanoma incidence increased annually from 2003 to 2016.  Average of 78,000 new melanoma diagnoses each year.  Without intervention, melanoma treatment costs are expected to triple by 2030.  Skin Cancer Prevention Initiatives  CDC estimates that a national skin cancer prevention program could prevent 230,000 melanoma cases.  The Surgeon General’s Call to Action (2014):Focused on skin cancer as a major public health issue.  Aimed to raise awareness and reduce sun exposure risks.  Melanoma Mortality Rates and Treatment Advances  Melanoma diagnosis continues to increase, but mortality rates have decreased by ~5% annually.  New treatments for advanced melanoma have contributed to this decline. Other Reactions to UVR Exposure  Common Photosensitivity Reactions:  Sunburn  Photo-aging Immunologic changes in the skin Cataracts  Photodermatoses,  phototoxicity,  Photoallergy  Drug- or chemical-induced: Phototoxicity & photoallergy account for up to 8% of adverse drug reactions.  Sunscreen Use and Its Effectiveness  Sunscreen and photoprotective behaviors help reduce UVR-related health issues.  Despite this, sunscreen use remains low:  Less than 15% of males and 30% of females use sunscreen as recommended.  42% of males report never using sunscreen. Etiology of Ultraviolet Radiation Exposure Understanding the UV Radiation Spectrum and Its Effects  Ultraviolet Radiation (UVR) and Photosensitivity  UVR is the primary cause of photosensitivity reactions in humans.  It is categorized based on four primary wavelengths:  UVA1: 340–400 nm  UVA2: 320–340 nm  UVB: 290–320 nm  UVC: 200–290 nm  UVA Radiation (320–400 nm)  Closest to visible light in wavelength.  Less erythemogenic than UVB but can cause deep dermal damage.  UVA Effects: Penetrates into the dermis and causes long-term skin damage, aging, and increased risk of skin cancer.  Prevalence: 10 to 100 times more UVA reaches Earth’s surface than UVB.  Contributes up to 15% of the erythemal response at midday.  UVB Radiation (290–320 nm)  The most erythemogenic (causes redness) and melanogenic (promotes tanning) of the UV bands.  UVB Effects: Primarily absorbed by the epidermis and can cause DNA damage, leading to skin cancer.  Up to 90% of UVB is blocked by the Earth's ozone layer.  Immune System Impact: UVB alters immune function, increasing the risk of skin cancers  UVC Radiation (200–290 nm)  UVC radiation is absorbed by the Earth's atmosphere and does not reach the surface.  Highly harmful if directly encountered (e.g., in artificial settings), but not a natural environmental concern. Types of Ultraviolet Radiation and Characteristics Beneficial Effects of UVB: Vitamin D Production  UVB exposure leads to the conversion of 7- dehydrocholesterol to cholecalciferol (Vitamin D3).  Vitamin D:  Essential for calcium homeostasis and bone health.  Reduces the risk of rickets in children.  Prevents fractures and osteomalacia in adults.  Small amounts of UVB exposure are beneficial for health.  UVC Radiation and Its Applications  Absorption by Ozone Layer:  UVC wavelengths (200–290 nm) are completely absorbed by the Earth's stratospheric ozone layer, preventing them from reaching the surface.  Artificial Sources of UVC: UVC radiation is used in germicidal lamps for:  Sterilization and food preservation.  Minimizing bacterial growth in laboratories and hospital operating rooms.  Environnemental Effets on Ultraviolet Radiation (UVR)  The amount of UVR reaching the Earth's surface is influenced by various environmental factors.  Ozone Layer and Pollution:  The ozone layer plays a critical role in blocking UV radiation, particularly UVB.  Ozone Depletion is caused by pollutants like chlorofluorocarbons (CFCs), nitrous oxide, and other greenhouse gases (GHGs).  Factors Influencing UV Radiation Exposure  Time of Day:  75% of daily UVR occurs between 9 AM and 3 PM.  Short shadows indicate higher UV intensity and a greater risk of sunburn.  2. Cloud Cover:  Clouds reduce UV and infrared radiation.  Reduced heat warning can increase the risk of UV overexposure.  3. Surface Reflection:  UV reflection from surfaces:  Sand and water reflect significant UV rays.  Snow also reflects harmful rays.  4. Other Factors:  Seasonal variations.  Geographic latitude and altitude impact UV levels.  Understanding the UV Index  The UV Index/Global UV Index( http://www.epa.gov/sunwise/uvindex.html)  1. Definition and Purpose:  The UV Index is a public health tool developed by the EPA, National Weather Service, and CDC.  Forecasts UVR intensity for each ZIP code worldwide, for the noon hour.  2. UV Index Scale:  Scale: 1 (low exposure) to 11+ (extremely high exposure).  3. Factors Influencing UVR Exposure:  Sun elevation: Higher sun, stronger UVR.  Ozone levels: More ozone, less UVR  Cloud cover:  Clear skies: 100% UVR.  Scattered clouds: 89%.  Broken clouds: 73%.  Overcast: 32%.  4. Skin Sensitivity: Darker skin requires more UVR exposure to cause erythema. Pathophysiology Erythema and oxygen free radicals The effects of UV radiation on the skin  Introduction to Erythema  Excessive exposure to UVR (Ultraviolet Radiation) leads to erythematous reaction in the skin.  Affects both epidermal and dermal layers.  Types of UVR: UVA and UVB radiation.  Mechanism of Erythema  UVA and UVB cause release of vasodilatory mediators like:  Histamine  Prostaglandins  Cytokines  These mediators increase:  Blood flow Erythema (skin redness)  Tissue exudates Swelling, Warmth sensation, Characteristic sunburn.  Effects of Severe UVR Exposure  Severe UVR exposure, especially UVB, can cause:  Blister formation  Desquamation (skin peeling)  Fever  Chills  Weakness  Shock.  UVA-Induced Changes in the Dermis  UVA causes significant damage to:  Vasculature (blood vessels)  Dense cellular infiltrates that penetrate deeper into the skin.  Role of Oxygen Free Radicals  UVR causes skin to absorb energy, which interacts with oxygen.  This leads to the formation of oxygen free radicals.  Impact: These free radicals cause tissue damage in the dermis.  Immediate Pigment Darkening vs. Delayed Tanning  Overview of Tanning:  Tanning is an adaptive response of the skin to UV radiation (UVR).  Primary cell involved: Melanocyte, which produces melanin to absorb radiation.  2. Immediate Pigment Darkening (Meirowsky Phenomenon):  Occurs during UVA exposure and certain visible light bands.  Caused by the oxidation of existing melanin in the epidermis.  Results in transient grayish-brown skin discoloration.  3. Influencing Factors for Immediate Darkening:  Duration and intensity of exposure.  Preexisting melanin or prior tanning.  Individual's skin type. 4. Limitations:  Immediate pigment darkening does not protect against UVB- induced erythema.  Photocarcinogenesis: Squamous Cell and Basal Cell Carcinoma  Overview:  UVR exposure is a major factor in the development of non-melanoma skin cancers (SCC and BCC).  These cancers most often occur on sun-exposed areas: Face, neck, arms, hands, and back of forearms.  2. Risk Factors:  Geographic proximity to the equator (higher risk closer to the equator).  Lower melanin content in the skin increases susceptibility.  Outdoor occupations elevate risk.  Family history of SCC/BCC increases risk up to twofold.  3. SCC vs. BCC:  SCC: Stronger link to UVR exposure than BCC.  Individuals with sensitive skin types are more prone to non-melanoma skin cancers.  Cutaneous Malignant Melanoma (CMM)  Link to UVR Exposure:  Primarily associated with UVR-induced sunburns.  Five or more severe sunburns during adolescence doubles the risk.  2. Risk Factors:  Geographic proximity to the equator and lower melanin content increase susceptibility.  Family history is significant: 8–12% of cases show a familial link.  3. Characteristics of CMM:  Unlike non-melanoma skin cancers, it is not clearly linked to cumulative UVR exposure.  Commonly occurs on intermittently sun-exposed areas:  Males: Back.  Females: Lower legs.  Predominantly affects middle-aged individuals and indoor workers.  Photoeffects on the Eye  Ocular Adverse Effects of UVR Exposure:  Cataracts:  Age-related opacification of the lens. Incidence increases after 50 years, affecting 30% of people over 74.  Caused by protein oxidation and precipitation in the lens.  Symptoms:  Blurred vision, halos around lights, color changes, and blindness.  Advanced treatment:  Surgical removal.  Conjunctival degeneration and proliferation  Squamous Cell Carcinoma (SCC) of the cornea and conjunctiva.  2. UVB and UVA Impact on the Eye:  UVB: Absorbed by the cornea and lens, causing slow oxidative damage.  UVA: Penetrates deeper structures, leading to cumulative damage.  3. Photokeratitis (Corneal Sunburn):  Symptoms: Painful corneal inflammation, conjunctivitis.  Onset: 30 minutes to 24 hours after exposure.  Recovery: Typically resolves in 24–48 hours due to corneal epithelium regeneration.  Treatment:Cool, wet compresses.  Mild anti-inflammatory analgesics: Ibuprofen, aspirin, or naproxen sodium.  Phototoxicity and Photoallergy  Phototoxicity:  Definition: A drug-induced inflammatory reaction caused by UVR exposure.  Mechanism: The drug or chemical acts as a chromophore, absorbing UVR.  Energy is transferred to surrounding molecules, causing tissue damage.  Key Factors: Reaction depends on the concentration of the chromophore in/on the skin.  Wavelength of UVR required is determined by the chromophore's absorption spectrum Photoallergy  Definition: A delayed hypersensitivity reaction mediated by the immune system.  Mechanism: Caused by polycyclic photosensitizers reacting with UVA to form antigenic macromolecules.  The agent becomes an antigen or hapten, triggering an immune response.  Differences from Phototoxicity:  Requires a sensitization period (prolonged or prior exposure).  Does not occur on first exposure.  Involves antigen-antibody processes or immune mediation.  Trigger: After sensitization, even minimal exposure can cause a reaction. Photo-protection Methods and Sunscreen Types  Overview of Photo-protection  Methods:  Sunscreens  Protective clothing  Sunglasses  Clothing and avoiding direct sunlight offer greater protection than sunscreen alone.  Types of Sunscreens  Sunburn Preventive Agents:  Absorb >95% of UVB radiation, preventing sunburn.  Sun-tanning Agents:  Absorb 85–95% of UVB radiation, allowing tanning without significant sunburn.  Chemical Sunscreens:  Include both sunburn preventive and suntanning agents.  Physical (Opaque) Sunblocks:  Reflect/scatter all UVA, UVB, and visible light, preventing sunburn and suntanning.  Broad-Spectrum Sunscreens:  Developed due to recognition of UVA’s role in adverse effects.  Combine UVA and UVB absorbers for enhanced protection.  Beneficial for individuals with photosensitivity to a broad range of wavelengths. Clinical Application of Photosensitivity  Importance of Skin Type in Patient History  Significance:  Skin type is a key factor in assessing UVR risk and photo-protection needs.  Classification of Skin Types:  Patients are categorized into six sun-reactive skin types based on:  Response to initial sun exposure.  Skin color.  Tendency to sunburn.  Ability to tan.  Personal history of sunburn. Indicators of Skin Reactivity to Sunlight  Hair and Eye Color as Indicators:  Higher Skin Reactivity:  Blonde, red, or light brown hair.  Blue or green eyes.  Lower Skin Reactivity:  Dark-colored hair and dark eyes.  History of Sunburn:  A history of severe sunburn may indicate higher skin sensitivity.  Self-reported sunburn/tanning histories can be unreliable.  Personal interviews are often a better assessment tool.  Key Considerations Before Recommending Sunscreen  1. Patient History Factors:  Medication history: Certain drugs can increase photosensitivity.  History of sun-reactive dermatoses: Conditions triggered by sun exposure.  Allergy history:  Focus on contact hypersensitivities to cosmetics or topical agents.  2. Intended Activities:  Evaluate the patient's planned outdoor activities to recommend appropriate protection (e.g., water-resistant, sweat-resistant products). Risk Factors  Long-Term Effects and Risk Factors of UVR Exposure  1. Long-Term Effects of UVR:  Photocarcinogenesis: Development of skin cancers.  Photoaging: Premature aging of the skin.  2. Key Risk Factors:  Congenital Pigmentation:  Skin type, hair, and eye color influence UVR sensitivity.  Exposure Factors:Intensity, duration, and frequency of UVR exposure.  Early childhood exposure increases risk significantly.  Children receive 3x more UVB than adults by age 18.  3. Skin Cancer Risks:  Malignant Melanoma:  Linked to frequent sunburns and intermittent high-intensity UVR exposure.  Mole-related risks:  Large congenital moles (>1.5 cm).  Multiple or abnormal moles.  Nonmelanoma Skin Cancers:  Associated with cumulative UVR exposure over a lifetime.  4. Family History and Behavior:  First-degree relatives of skin cancer patients have higher risk.  Contributing behaviors:  Frequent sunburns, poor sunscreen use, and tanning bed usage.