Unit 6 lec

• Sun Protection Basics:

  • Light Spectrum is defined by the size of the wavelength, frequency, and energy
  • Radio waves have the lowest spectrum, while gamma rays have the highest energy and shortest wavelength
  • UVC and approximately 90% of UVB radiation are absorbed by ozone, water vapor, oxygen, and carbon dioxide
  • UVA radiation is less affected by the atmosphere and reaches the earth's surface
  • The sun emits a constant flow of energy in a spectrum of wavelengths
• UV Radiation Classification:

  • UVC (100 to 280 nm) is blocked out by the ozone layer
  • UVB (280 to 320 nm) penetrates the superficial skin layers and is a major cause of sunburn
  • UVA (320 to 400 nm) penetrates down to the dermis and causes skin tanning/browning
• Sun Protection Factor (SPF):

  • SPF indicates how long it takes for UV rays to redden protected skin compared to unprotected skin
  • SPF value increases as sunburn protection increases
  • SPF is measured in terms of redness (erythema) after sun exposure
  • SPF 15 blocks 93% of sun rays, but there is still 7% that can penetrate the skin
  • The higher the SPF number, the better the protection if applied appropriately
• Influencing Amount of UV Radiation:

  • Factors like altitude, geography, time of year, time of day, weather conditions, reflection, skin type, amount of sunscreen applied, and reapplication frequency influence UV exposure
• Broad-spectrum protection in sun care products:

  • Protects against both UVA and UVB rays
  • Some countries specify broad-spectrum protection on labels
  • Sunscreens with even a high SPF value may not provide adequate protection against UVA radiation
  • Broad-spectrum products with SPF 15 or higher can reduce the risk of skin cancer and early skin aging
• Water resistance in sunscreens:

  • Products can be labeled as "water resistant" or "very water resistant" based on how long they retain the stated SPF after immersion in water/sweat
  • Terms like "sunblock," "waterproof," and "sunproof" are not allowed on product labels
  • Sunscreens cannot claim to provide sun protection for more than 2 hours without reapplication
• Effects of UV radiation:

  Positive effects:

  • UVB light catalyzes Vitamin D production in human skin
  • UV radiation can be helpful in treating skin conditions like psoriasis, eczema, acne, and certain fungal skin infections
  • Sun exposure can reduce the severity of depression in patients with seasonal affective disorders
• Negative effects of UV radiation:

  • Tanning is a sign of skin damage and accelerates aging
  • UV radiation is the main cause of non-melanoma skin cancers
  • Linked with eye diseases like cataracts and retinal degeneration
  • Causes photoaging and premature wrinkles
• UV radiation and SPF:

  • Dark skin, with more melanin, is better protected against UV-induced damage
  • Melanin absorbs about 50-75% of UVR, providing some protection
  • Different skin types allow varying percentages of UVB and UVA to penetrate
• Types and definition of suncare products:

  • Sunscreens are practical for photoprotection and contain UV filters
  • Available in various forms like creams, lotions, sticks, wipes, gels, and aerosols
  • Primary sunscreens provide direct skin protection, while secondary sunscreens have other primary uses
• After-sun products:

  • Designed for use after exposure to the sun or UV radiation
  • Help moisturize the skin, provide a cooling effect, and relieve pain from sunburn
  • Available in forms like lotions, creams, and gels
• Qualities and characteristics of sunscreens:

  • Provide protection against both UVB and UVA radiation
  • Allow some tanning while protecting the skin
  • Water-resistant and alleviate pain, soothe, and moisturize the skin
• Technical qualities of sun care products include:

  • Drying time and absorption after application
  • Easy spreadability
  • User-friendly to encourage frequent application and provide reliable protection
  • Non-toxic, non-irritant, and non-sensitizing
• Sun care products should have proven efficacy and/or performance, long-term stability, appropriate texture, appropriate rheological properties, stability to heat and UV radiation (photostability), and dermatological safety
• UV filters in sun care products are classified as physical and chemical sunscreens
• Physical sunscreens (inorganic UV filters) reflect and scatter UV radiation, providing broad-spectrum protection
• Inorganic UV filters like titanium dioxide and zinc oxide are approved UV filters that offer broad-spectrum protection
• Chemical sunscreens (organic UV filters) generally consist of aromatic compounds and absorb UV rays
• Organic sunscreens can penetrate the skin due to their lipophilic nature, which may raise safety concerns
• Chemical sunscreens contain UVB absorbing filters like octinoxate, octisalate, and padimate O, and UVA absorbing filters like avobenzone, oxybenzone, and meradimate
• UVA filters include benzophenone, avobenzone, meradimate, and other compounds
• UVB filters interact with UV radiation through reflection, scattering, and absorption effects
• Inorganic sunscreens like zinc oxide and titanium dioxide provide UVA and UVB protection
• The PA rating system categorizes the level of UVA protection in sunscreens
• Sunscreen product forms include emulsions, sticks, aerosol sprays, ointments and oils, gels, and wipes
• Sunburn is an inflammatory reaction from prolonged exposure to sun UV radiation, resulting in damage to the skin's outermost layers
• Ingredients of sunburn products include soothing and anti-inflammatory agents, cooling agents, antioxidants, and moisturizers
• Additional sunburn ingredients include waterproofing agents, photostabilizers, and emollients
• UV filters like octocrylene, TiO2, and polyester-8 are examples of substances that help increase water resistance and serve as solvents for organic sunscreens
• Emollients are lipophilic ingredients that help increase water resistance and serve as solvents for organic sunscreens
• Examples of emollients include mineral oil, shea butter, castor oil, cocoa butter, isopropyl myristate, paraffin, and silicones
• Water is an essential component for emulsions and gels and serves as a solvent for water-soluble ingredients
• Emulsifiers provide product stability. Examples include glyceryl stearate, PEG-100 stearate, cetyl alcohol, and cetyl dimethicone copolyol
• Thickeners act as rheology modifiers and affect product application, spreadability, and efficacy of sunscreens. Examples include carbomers, cellulose derivatives, gums, and lipophilic thickeners like waxes
• Film-forming ingredients, also known as "SPF boosters," help form an even and uniform film on the skin after application and drying, allowing for a higher SPF value. Examples include hydrolyzed wheat protein/PVP crosspolymer, methylcellulose, and polyester-7
• Antioxidants help prevent oxidative reactions. Examples include vitamins E and C
• Preservatives protect water-based product formulations. Examples include parabens, benzyl alcohol, methylisothiazolinone, methylchloroisothiazolinone, and phenoxyethanol
• Humectants provide moisturization. Examples include sorbitol, glycerin, and propylene glycol
• Chelating agents contribute to the stability of the system by forming complexes with metal ions that may cause premature deterioration of the products. Examples include EDTA and its derivatives
• Propellants help expel the content of the aerosol can. Examples include isobutane and dimethyl ether