Functional categories of skin care ingredients

A brief description of main categories of skin care ingredients by their function/activity.

Antioxidants:
Substances that neutralize free radicals. Damage by free radicals is one of the key mechanisms of the aging process. Also, free radicals mediate many forms of inflammation. Antioxidants reduce the skin's exposure to free radicals. Not all antioxidants are not created equal, they vary by the range of activity, solubility in oil and water, and other properties.

Binding Agents:
Substances that hold products together and prevents separation of the water and lipid components. The most important binding agents in skin care are emulsifiers (see below).

Bioactive agents:
A diverse, imprecisely defined group of substances affecting biological processes. Many, such as growth factors and hormones, works as molecular signals activating or suppressing particular biological functions in cells.

Delivery Enhancers/Systems:
Ingredients that enhance delivery of other ingredients into the skin and/or insider skin cells.

Emulsifiers:
A smooth blend of oil and water. Since most skin care product formulas include both water and oil soluble ingredients, emulsions are very popular in skin care. Most creams and lotions are emulsions. However, emulsions are unstable and quickly separate. Emulsifiers are substances that stabilize emulsions and prevent products from separating.

Emollients:
Substances that smooth and soften the skin. There exist a wide variety of emollients, each providing its own individual texture to the skin.

Humectants:
Substances that can attract water, usually out of the air. By definition, all are also moisturizers. In fact, any good moisturizer has to contain potent humectants.

Lubricants:
Substances that make skin feel smoother to the touch and reduce friction; more common in hand creams.

Preservatives:
Substances that kill detrimental bacteria, yeast and/or molds, thus prevent spoilage. While some preservatives may occasionally be irritating to the skin, the use of products spoiled by microorganisms may be equally or more damaging. Sometimes antioxidants and stabilizers are also referred to as preservatives because they inhibit chemical degradation of products.

Solvents:
Substances, such as alcohol or water, which dissolve other ingredients.

Surfactants:
Wetting agents, substances capable of reducing the surface tension of a liquid in which it is dissolved. In skin care, surfactants enable a topical product to easily spread and glide across the skin.

Vehicle:
The base that carries the active ingredients.

Vitamins, nutrients, metabolites:
A diverse group of substances needed for proper nutrition, metabolism and other functions of skin cells. Some have proven clinical benefits. Many others are unproven as far as skin care applications are concerned.

Source : Smartskincare