How Do Moisturizers Work?
Traditionally, moisturization was believed to inhibit water loss. Water originates in the deeper skin layers and moves upward to the cells in the stratum corneum, eventually being lost to evaporation. Occlusive moisturization then, prevents the dehydration of the stratum corneum.
Much more is now known about the epidermis, and in particular, the stratum corneum. Dry skin is noted when the moisture content is less than 10%, and there is loss of continuity of the stratum corneum.

Scientifically, the moisturizing treatment involves a 4-step process:
Repairing the skin barrier
Increasing water content
Reducing water loss

Restoring the skin’s ability to attract, hold and redistribute water
Class

How does it Work?

Example ingredient

What is it used for?

Possible side effects

I. Occlusive
It Physically blocks water loss
Petrolatun
Lanolin
Mineral
Oil
Zinc Oxide
Xerosis
Atopic dermatitis
Prevention of irritant contact dermatitis
Messy
Some can cause folliculitis (mineral oil)
May cause pimples
Some may cause contact dermatitis (lanolin)

II. Humectants
Attracts water to the stratum corneum
Glycerin
Sorbitol
Urea
Alphahydroxy acids
Sugars
Xerosis
Ichthyosis
Skin rejuvenation
Some may cause irritation (urea, lactic acid)

III. Emollients
Smoothes skin by filling the spaces between skin flakes, with droplets of oil
Cholesterol
Squalene
Fatty Acids
Reduces skin roughness
They’re not always effective

IV. Rejuvenators
They claim rejuvenate the skin by replenishing essential proteins
Collagen
Keratin
Elastin
Skin rejuvenation
Unlikely to work because the protein molecules are too large to cross the epidermis
Some may cause contact dermatitis