MOISTURIZERS: OCCLUSIVES AND HUMECTANTS

There are two principal preparations intended for preserving the moisture of the skin:
occlusives
humectants


Occlusives
Occlusives produce an oily layer on the skin, enriching the skin’s natural lipid film, which prevents water evaporation. The keratinous layer dampens, becoming more fully saturated with water.


These products are more effective if applied directly after washing, trapping a layer of water beneath them. Substances such as the following can be used:
Mineral-derived fatty compounds such as paraffin or petroleum jelly (the most common mineral source is crude oil, from which various oils can be derived after refining). Cetomacrogol is another occlusive, mineral-derived compound that can be found in various moisturizers. Moisturizers based mainly on minerals are highly effective, but they are sticky and greasy. They are intended for people with very dry skin or for those having certain skin medical problems. 
Substances derived from animal fat, such as lanolin and its derivatives (derived from sheep’s
wool). 
Vegetable oils such as olive oil, oat oil, peanut oil, sesame seed oil, and many others. Vegetable oils are less occlusive than animal-derived oils or mineral oil, yet allow sufficient occlusion.
 
Note: 
Oily products all function in the same way, preventing water evaporation fromthe superficial layers of the skin. There is no significant difference among the various fatty products derived from animals. None have any proven age-reversing abilities. Oils derived from rare animals are not superior, and their use is only an uncalled-for commercial gimmick. Some moisturizing products contain a substance called spermaceti, which is produced from whales. The use of these products is prohibited in the United States. Those consumers who have reservations about the killing of whales should avoid using products containing this substance. One can read the label of contents on the product to ensure that it does not contain spermaceti

Remember that occlusive products tend to be sticky and oily, so consumers will generally refrain from using products that appear in an oilier form (such as an ointment). Therefore, these products are generally combined as creams or lotions (which have a greater water content). These are easier to apply and are preferred by most consumers. After water evaporation, the occlusive components that remain will protect the skin and fulfill their function..


Humectants
Humectants absorb water. This group includes numerous substances, some of which are able to penetrate the keratinous layer and increase its water content. Other products from this group have large molecules that do not penetrate the keratinous
layer, but form a hygroscopic (water-absorbing) layer on the skin. The effectiveness of several
of these products is debatable. In a relatively arid environment, they may actually absorb water
from the skin (rather than the environment), causing increased dryness. On the other hand, in
a humid environment, they are clearly efficient. In conclusion, their efficacy is not as great as
occlusive products in a cold, dry environment. Therefore, an efficient moisturizer suited to cold,
dry weather, should contain a combination of occlusives and humectants.
In daily usage, moisturizing cosmetics made only from water-absorbing substances are
called nonoily moisturizers.
From a practical point of view, the various approaches to skin moisturizing are not distinctly
segregated. Most moisturizers have a number of components from each group. They
usually contain occlusive, oily products along with humectants. In addition, a number of the
components have a combined effect: lanolin and its derivatives, for example, are occlusives but
they have a certain degree of absorptive capacity as well.