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Dermatology
Sunscreens and Photoprotection
Built from Dermatology, 5th Edition
What’s inside
6 sections · 83 slides
Overview
- What this topic covers
- Why sun protection matters
History and Regulation
How sun protection began, and how sunscreens are tested, labeled, and regulated today
- Sun exposure: a changing attitude
- Awareness has not changed behavior
- Early history of sunscreen products
- From sunburn prevention to broad protection
- UVB, UVA2, and UVA1 wavelength ranges in sunlight
- How sunscreens are regulated in the US
- Global rules vary widely
- Global comparison of efficacy testing and labeling of sunscreens
- Global comparison of efficacy testing and labeling of sunscreens (continued)
- Global comparison of efficacy testing and labeling of sunscreens (continued)
- Sun protection factor (SPF): what it means
- SPF value versus the percentage of erythemal UV filtered
- Determination of the sun protection factor (SPF)
- Why UVA protection is harder to test
- Critical wavelength: the main lab test for UVA
- Critical wavelength and UVA1/UV ratio testing
- FDA sunscreen rules, 1999 to today
- The 1999 and 2011 FDA rules
- The 2019/2021 proposed rule: safety first
- FDA proposed order (2021) for GRASE status of sunscreen active ingredients and dosage forms
- What the GRASE categories mean in practice
- FDA proposed order on sunscreens (2021) – ultraviolet B (UVB) and ultraviolet A (UVA) protection and labeling requirements
- Getting a brand-new sunscreen ingredient approved
Mechanisms and Active Ingredients
How sunscreen filters absorb or scatter UV light, and the specific agents used to do it
- How a sunscreen physically works
- Two families of active ingredient
- What happens when an organic filter absorbs UV
- Fixing unstable filters: photostabilizers
- Mineral filters: from "sunblock" to modern micronized form
- Active ingredients in sunscreens by absorption spectrum
- PABA and its relatives
- Cinnamates and salicylates
- Benzophenones
- Other organic filters used today
- Filters used abroad but not yet approved in the US
- Mineral (inorganic) filters
- Other photoprotective agents (not classed as active filters)
Sunscreen Benefits: the Evidence
What controlled human studies show about sunburn, aging, immune effects, and cancer prevention
- Five kinds of sun damage a sunscreen should prevent
- Action spectra for UV-induced skin damage
- UVB versus UVA: a lopsided comparison
- Why proving cancer or aging prevention is hard
- Sunburn: why real-world protection often falls short
- Sunscreen physically blocks sunburn
- Photoaging: does daily sunscreen actually help?
- Photoimmune suppression: UV can weaken skin immunity
- Measuring immune protection versus sunburn protection
- Sunscreen and actinic keratoses (pre-cancer spots)
- Larger trials confirm fewer skin cancers with sunscreen
- Sunscreen benefit in organ transplant recipients
- Melanoma: nevi (moles) as an early warning sign
- Melanoma risk: a genuinely mixed evidence base
- Two theories behind the melanoma controversy
- The strongest melanoma-prevention evidence available
- Photosensitivity disorders: a different challenge
Sunscreen Safety
Skin reactions, systemic absorption, environmental questions, and the vitamin D debate
- Decades of use, an overall excellent safety record
- Irritation and allergy: common versus rare
- Lay-press safety concerns, examined
- Are nanoparticle mineral filters risky?
- How much sunscreen enters the bloodstream?
- Other reported safety questions
- Environmental concerns: sunscreens and coral reefs
- Policy response to the coral bleaching concern
- Sunscreen and vitamin D: how the link works
- The vitamin D "sufficiency" debate
- Getting enough vitamin D without unsafe sun exposure
Clothing and Photoprotection Strategy
Protective clothing standards, and how to combine shade, clothing, and sunscreen sensibly
- Photoprotective clothing: an unregulated space in the US
- UV Protection Factor (UPF): SPF for fabric
- What makes a fabric protective
- Sunscreen as the "last line of defense"
- Guidelines for photoprotection
- Special populations
- Key takeaways
- References
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- Dermatology, 5th Edition (2-Volume Set)