Unit 5 lec

• Skin Moisturizers:

  • Designed to improve skin quality, maintain or restore moisture content of the stratum corneum
  • Keep skin smooth, pliable, hydrated, and alleviate dry skin symptoms
  • Used after proper skin cleansing
• Qualities of Skin Moisturizers:

  • Neutral or pleasant odor and color
  • Easy to spread, pleasant feeling during application
  • Non-oily/greasy after application
  • Non-comedogenic (do not block pores)
  • Provide effective hydration, prevent transepidermal water loss
  • Protect from environmental factors, reduce dryness, improve dull appearance
  • Smoothen and soften the skin
  • Well-tolerated and non-allergenic
• Moisturizers:

  C1. Humectants:

  • Hygroscopic ingredients that increase water content of the skin's top layer
  • Replace the skin's Natural Moisturizing Factor (NMF)
  • Examples: AHAs, pyrrolidone carboxylic acid, glycerin, hyaluronic acid

  C2. Emollients:

  • Soften and smoothen the skin, fill void spaces between corneocytes
  • Examples: Hydrocarbons, fatty acids, vegetable oils, silicones

  C3. Occlusives:

  • Create a hydrophobic barrier to block transepidermal water loss
  • Examples: Petrolatum, silicone derivatives like dimethicone

  C4. Skin Rejuvenators:

  • Enhance skin's barrier function, reinforce skin hydration
  • Leave a protein film to smoothen skin and stretch fine wrinkles
• Ingredients in Skin Moisturizers:

  • Emulsifiers: crucial for emulsion stability
  • Thickening agents: contribute to stability and skin feel
  • Water: basic component of emulsions
  • Preservatives: inhibit bacterial growth
  • Antioxidants: prevent oxidation
  • Fragrances: improve aesthetic qualities
  • Sunscreens: protect from sunlight radiation
  • Colorants: enhance aesthetic quality
  • Electrolytes: improve stability
  • Functional ingredients: natural additives, vitamins, peptides, proteins
• Skin Moisturizers:

  • Facial moisturizers are usually O/W or W/Si emulsions
  • Hand and body moisturizers are commonly W/O emulsions
  • Multiple emulsions allow sustained release of entrapped materials
  • Barrier creams prevent irritant dermatitis
• In single-celled organisms, substances can easily enter the cell due to a short distance, while in multicellular organisms, the distance is larger because of a higher surface area to volume ratio
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen due to their higher surface area to volume ratio
• W/O/W Emulsions, also known as Multiple Emulsions, are used to sustain the release of entrapped materials in the internal phase and for using incompatible ingredients in the same formulation
• Barrier Creams/Skin protective creams are a specialty product type used to avoid unpleasant reactions and prevent irritant dermatitis caused by other types of skin
• For normal skin, humectants and emollients are added; for dry skin, humectants, emollients, and occlusive agents are added; for oily skin, water-based gels and lotions are recommended
• Determination of Emulsion Type:

  F1. Conductivity Measurement:

  • An assembly with electrodes dipped into the emulsion
  • Principle: water is a good conductor of electricity, determining the type of emulsion

  F2. Solubility:

  • Using oil-soluble or water-soluble dye to stain and check the emulsion under a microscope

  F3. Dispersion by Dilution:

  • Emulsions can be diluted with their external phase to determine stability
• Evaluation of Moisturizing Effect:

  G1. Skin Hydration:

  • Conductance Method and Capacitance Method are commonly used techniques

  G2. TEWL:

  • Measures the amount of water vapor leaving the skin
  • Open Chamber Devices like Evaporimeter® and Tewameter® are used
  • Closed Chamber Devices like VapoMeter® can measure humidity and diffusion gradient
• Evaluation of Moisturizing Effect (contd):

  G3. Desquamation:

  • D-squame® is used to sample the skin surface and determine dryness and scaling

  G3. Sebum:

  • Sebumeter® measures the amount of sebum on the skin surface
• Aesthetic Properties are tested by experts or volunteers and include factors like rub-out, appearance, pick-up, greasiness, tackiness, break, slip, after-feel, and delayed after-feel