Page 250 - Cosmetology

pristane. Technically tetramethylpentadecane or pentadecane. It is a component of mineral oil, shark oil, or
plant oil. It is used as an emollient in cosmetics.

progesterone USP. A study published in the American Journal of Obstetrics and Gynecology (June 1999,
pages 1504–1511) states that "In order to obtain the proper (effective) serum levels with use of a
progesterone cream, the cream needs to have an adequate amount of progesterone in it [at least 30
milligrams per gram]. Many over the counter creams have little [for example, 5 milligrams per ounce] or none
at all. The creams that are made from Mexican yams are not metabolized to progesterone by women. The
cream used in the above study (Pro-Gest) contains pure United States Pharmacopoeia [USP]
progesterone." Dr. John Lee, an author and longtime proponent of topically applied progesterone, explains
that "The USP progesterone used for hormone replacement comes from plant fats and oils, usually a
substance called diosgenin, which is extracted from a very specific type of wild yam that grows in Mexico, or
from soybeans. In the laboratory, diosgenin is chemically synthesized into real human progesterone. Some
companies are trying to sell … ‘wild yam extract' [or other plant extracts] … claiming that the body will then
convert it into hormones as needed. While we know this can be done in the laboratory, there is no evidence
that this conversion takes place in the human body." Dr. Lee is quick to explain that he doesn't sell any of
these products and receives no profit from their sale. He also does not recommend the use of natural
progesterone creams with any other active hormones or herbs.

prolamine extract. Protein that has water-binding and antioxidant properties.

proline. See amino acid.

propagermanium. See germanium.

propolis. Brownish, resinous material that is collected by bees and used to construct the hive. It has
antibacterial and anti-inflammatory properties for skin.

Propylene Carbonate. Liquid used as a solvent and film-forming agent. See film-forming agent.

propylene glycol. Along with other glycols and glycerol, this is a humectant or humidifying and delivery
ingredient used in cosmetics. There are Web sites and spam e-mails stating that propylene glycol is really
industrial antifreeze and that it is the major ingredient in brake and hydraulic fluids. These sites also state
that tests show it to be a strong skin irritant. They further point out that the Material Safety Data Sheet
(MSDS) on propylene glycol warns users to avoid skin contact because systemically (in the body) it can
cause liver abnormalities and kidney damage. As ominous as this sounds, it is so far from the reality of
cosmetic formulations that almost none of it holds any water or poses real concern. It is important to realize
that the MSDS sheets are talking about 100% concentrations of a substance. Even water and salt have
frightening comments regarding their safety according to the MSDS. In cosmetics propylene glycol is used in
only the smallest amounts to keep products from melting in high heat or freezing when it is cold. It also helps
active ingredients penetrate the skin. In the minute amounts used in cosmetics, it is not a concern in the
least. Women are not suffering from liver problems because of propylene glycol in cosmetics. And finally,
according to the U.S. Department of Health and Human Services, within the Public Health Services Agency
for Toxic Substances and Disease Registry, "studies have not shown these chemicals [propylene or the
other glycols as used in cosmetics] to be carcinogens".

Propylene Glycol Stearate. Mixture of propylene glycol and stearic acid used as a skin-conditioning agent
and emulsifier. See propylene glycol and stearic acid.

propylparaben. See parabens.

proteases. Enzymes that are part of a process that causes the breakdown of amino acids and proteins in
skin. There is research showing that proteases, when applied topically to skin, can reduce the visible scaling
associated with dry, flaky skin. Whether proteases can be of benefit for wound healing when applied
topically is unclear.

protein. Proteins are fundamental components of all living cells and include a diverse range of biological
substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of
any organism, plant, or animal. The human body contains perhaps 100,000 different proteins, each
composed of an assortment of 20 or so amino acids. The sequence of these amino acids determines the
unique properties of each protein, such as, for example, its role as an enzyme acting as a catalyst for a
specific biochemical reaction. If even one of the essential amino acids is missing, the protein cannot be