Core Points - Sunscreen is essential for both beauty and skin barrier protection, with a focus on preventing damage from UVB and UVA rays [3] - Different types of sunscreen include physical and chemical options, each with distinct properties and suitability for various skin types [3] - SPF and PA ratings are critical indicators of sunscreen effectiveness against UVB and UVA rays, respectively [4] Group 1: Sunscreen Types and Mechanisms - Physical sunscreen includes inorganic agents like titanium dioxide and zinc oxide, which reflect UV rays and are suitable for sensitive skin [3] - Chemical sunscreen uses organic compounds that absorb UV rays, offering a lighter texture but may have stability and sensitivity issues [3] Group 2: Choosing Sunscreen Based on Activity - For outdoor activities, protective clothing and accessories are recommended, while specific SPF and PA ratings should be chosen based on exposure levels [4] - In high UV environments like beaches or mountains, higher SPF and PA ratings are advised, with waterproof options for activities involving sweat or water [4] Group 3: Special Considerations for Different Populations - Infants under 6 months should avoid sunscreen, relying on clothing and shade for protection, while older infants can use low-SPF physical sunscreens [5] - Elderly individuals and pregnant women have specific sunscreen needs, focusing on physical options and simple formulations to prevent skin issues [5] Group 4: Remedies for Sunburn - Immediate treatment for sunburn includes cold compresses and specific solutions available at pharmacies, with medical attention required for severe symptoms [5]

Core Viewpoint - Excessive sun protection measures can lead to vitamin D deficiency, resulting in osteoporosis due to insufficient calcium absorption [3][6]. Group 1: Understanding Osteoporosis - Osteoporosis is a metabolic bone disease characterized by decreased bone formation and increased bone resorption, leading to fragile and porous bones [1]. - Insufficient vitamin D absorption due to excessive sun protection can cause calcium deficiency, which is a key factor in the development of osteoporosis [3]. Group 2: Importance of Sun Exposure - While sun protection is necessary, some exposure to ultraviolet (UV) rays is essential for vitamin D synthesis [3][16]. - It is recommended to have 10-15 minutes of sun exposure without protection during non-peak hours to aid in vitamin D production [16]. Group 3: Effective Sun Protection Strategies - Proper sun protection should balance UV exposure and vitamin D synthesis; full coverage can hinder vitamin D absorption [3][10]. - Recommended sun protection measures include using products from reputable manufacturers and applying sunscreen 20-30 minutes before sun exposure [10][12]. - Different SPF levels are suggested based on activity: SPF 15 for daily use, SPF 25-35 for outdoor activities, and SPF 35-50 for beach outings [14].