Lecture 4 Flashcards
External causes of dry skin
Low humidity, air currents, solvents, UV radiation
Intrinsic factors of dry skin
Impaired SC function, Reduced sebum production, dietary deficiency
Emollients
provide partial occlusion that soothes, moisturizes, and improves appearance of the SC by masking rough, scaly skin
Occlusive Agents
form a film on the surface of the skin and moisturize by retaining water in equilibrium within the skin
Humectants
bind water from the environment and help by retaining water in equilibrium within the skin
Enhancers of skin barrier
mimic the SC bilayers structure and assure long-lasting moisturization
Criteria of selecting emollient ester and occlusive ingredients
Structure, polarity, spreading behavior, mol weight, viscosity, stability, solubilizing behavior, permeability into skin, and moisture retention
High MW esters
deliver low spreading
Low MW esters
deliver high spreading
Low viscosity emollients
Deliver High spreading
High viscosity emollients
Deliver low spreading
Squalane (C 30)
Saturated branched chain hydrocarbon. Colorless, odorless, transparent, chemically stable, inert, does not oxidize or turn rancid. part of sebum
Fixed oils
liquid triglycerides - fatty acid storage in oil seeds
Butters & Fats
semi-solid triglycerides - usually melting above or near ambient temperature
Waxes
distinctly solid lipids primarily fatty acid esters
Iodine value
chemical interaction with molecular iodine, measure of unsaturation - dbl bonds
PUFA
polyunsaturated fatty acids - high iodine
Acid value
alkali KOH neutralization/titration, measures free fatty acids
Saponification value
alkali KOH hydrolysis/titration, measures triglyceride esters
Unsaponifiables
determine % of, includes sterols, tocopherols, triacontanol hydrocarbons (squalene)
Peroxide value
measure of the degree of oxidation of a particular oil sample
Lanolin
classified as wax, composed of alcohol and sterol ester - “wool wax”. Very complex but has a lot of high MW molecules.
Esters
formed form reaction between a fatty acid and a fatty alcohol.
Humectants
Hygroscopic, have hydroxyl groups, act as freeze point depressants, act as skin moisturizers, maintain an equilibrium with water vapor in air.
