L11: Skin Physical Enhancers and Skin Hydration Flashcards
What are the 5 different physical penetration enhancers?
- Ionthophoresis
- Ultrasound
- Electroporation
- Thermal ablation
- Microneedles
What is ionthophoresis?
Application of a small electric current to the skin for charged molecules to diffuse across (via repulsion)
How does ultrasound work as a physical enhancer?
Use ultrasound waves to generate small bubbles of water on the surface of the skin
How long does ultrasound treatment stay effective for?
24 hours
What is the limitation of ultrasound as a physical enhancer?
Some substances may be degraded
How does electroporation work as a physical enhancer?
It ultilizes high voltage for short durations to create transient pores across the skin
What is a limitation of electroporation?
It may affect deeper tissues and cause pain and muscle contractions.
How does thermal ablation work as a physical enhancer?
Applies localised heat for a short period of time to create micropores across the stratum corneum
It liquefies the fats in the stratum corneum, thus temporarily facilitating passage of the cosmetic product into the skin (possibly via intercellular route)
What are the different types of microneedles?
- Solid microneedle
- Coated microneedle
- Dissolving microneedle
- Hollow microneedle
How much water content does the stratum corneum contain?
15 - 30%
How much water content does the epidermis contain?
70%
How does the skin minimise water loss?
- Low water content in the stratum corneum
- Physical barrier by the skin
- Presence of lipids in the stratum corneum
What does a high TEWL mean?
May suggest skin disease, as the water loss from skin is higher than normal, and that the skin integrity is being compromised
What is a critical environment condition that should be kept constant when measuring TEWL?
Humidity
What are some of the main natural moisturizers found in the skin?
- Natural moisturizing factors (NMF)
- Hyaluronic acid (HA)
- Aquaporin-3
- Glycerol
How much does NMFs constitute the stratum corneum?
20 - 30% dry weight
Other than containing NMFs, what other features does the cells at the stratum corneum possess to minimise TEWL?
Presence of tight junctions between cells
What are oil-in-water emulsion cosmetics used for?
Day creams
What are night creams made up of?
water-in-oil emulsions
Why do we need preservatives in cosmetic products?
To prevent microbial growth that may cause spoilage of cosmetic product, especially those with high moisture content
What is the most commonly used preservative in moisturizers?
Parabens
What are the main classes of ingredients used for skin hydration?
- Charged surfactants
- Occlusive agents
- Humectants
- Hydrophilic matrices
- Sunscreens
- Emollients
What is the function of occlusive agents?
To retard TEWL
What are some examples of occlusive agents?
- Petrolatum (most occlusive)
- Paraffin
- Lanolin
- Lecithin
- Cholesterol
- Demethicone (lighter kind of occlusive; also has emollient properties)
(usually fatty and oily substances)
What is the function of humectants?
Absorb water from the surroundings
What property must a humectant possess?
Hygroscopicity
What are some examples of humectants?
- Glycerin/glycerol
- Hyaluronic acid
- Sodium lactate
- Urea
- Propylene glycol
- Pyrrolidone carboxylic acid (PCA)
- Butylene glycol
- Panthenol
- Lactic acid
Which humectant is used as an exfolitating agent as well?
Lactic acid
What is a secondary benefit of keeping your skin moisturized?
Reduce wrinkles
Which humectant is used as a chemical skin permeation enhancer as well?
Propylene glycol
Which humectant is used as a preservative as well?
Butylene glycol
Which humectant has soothing and sedative properties?
Pathenol
Which humectant is the most powerful?
Sodium salts of PCA
What are hydrophilic matrices and what are they used for?
They are large molecular weight substances that retard TEWL
What are some examples of hydrophilic matrices?
- Hyaluronic acid
- Vitamins
- Collagen
How does hyaluronic acid work as a hydrophilic matrix?
Able to absorb up to 1000x its own weight of water
Provide mechanical support to the skin
Describe the process of desquamation.
As corneocytes move up the epidermis towards the stratum corneum, the desmosomes that connects between the cells get degraded by intercellular enzymes
Eventually, the corneocytes will be released as dead skin
What is the function of emollients?
Filling the space between the desquamating corneocytes with oil droplets, so they make the skin feel smooth
Is the effect of emollients permanent of temporary?
Temporary
What are some examples of emollients?
- Propylene glycol
- Jojoba oil
- Dimethicone
- Sesame oil
