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Kaolin - Kukui Nut Oil

Beauty and Cosmetic Glossary - K


kabuki brushes.  This brush is used to apply loose powder after you have applied foundation to set it. Sometimes these brushes are also referred to as Large powder brush.

kaolin. Natural claylike mineral (silicate of aluminum) that is used in cosmetics for its absorbent properties.

Kathon CG. See methylchloroisothiazolinone.

katrafay oil. Emollient plant oil that may have anti-inflammatory properties; however there is no research supporting this use.

kava-kava extract. Extract of the Piper methysticum plant that has analgesic (anti-inflammatory) properties, but can also cause skin irritation and dermatitis (Sources: Alternative Medicine Review, December 1998, pages 458-460; and Clinical Experimental Pharmacology and Physiology, July 1990, pages 495-507).

kawa extract. See kava-kava extract.

kelp extract. See algae.

kelpadelie extract. Common name for an extract from Macrocystis pyrifera. See algae.

kerastase nutritive.  The Kerastase Nutritive Collection gives the correct level of nutrition to the hair without weighing it down. Hair feels soft, supple and tangle-free, whatever the degree of sensitivity.

Khaya senegalensis extract. May have some antimicrobial properties (Sources: Phytochemistry, November 20, 1998, pages 1769-1772; and Phytomedicine, July 1999, pages 187-195).

Khus khus extract. See vetiver oil or extract.

Kigelia africana extract. Extract of an African plant commonly known as the sausage tree. The African lore about this extract is that it can firm breast tissue, but there is no supporting research for this myth, or that indicates this plant has any other benefit for skin.

kinetin. The trade name for kinetin is N6-furfuryladenine. It is a plant hormone responsible for cell division. As a "natural" skin-care ingredient it is primarily being promoted as having been clinically proven to reduce the signs of aging, improve sun damage, reduce surfaced capillaries, and offer many other skin benefits of particular interest to aging baby boomers. There is a good deal of research on kinetin when it comes to plants or in test tubes (in vitro), with cells, or even on flies, but there is no published research on kinetin's topical effect, either on animal or human skin (Source: Dermatologic Clinics, October 2000, pages 609-615).

However, there are two unpublished clinical studies responsible for much of the attention kinetin is getting. Both were sponsored by Senetek, the company licensing the use of kinetin. On a closer look, according to (an Internet source evaluating the legitimacy of medical research), the data are far less convincing than Senetek would want you to know. The two studies, paid for by Senetek, were both done by Dr. Jerry L. McCullough, professor of dermatology, University of California, Irvine. According to MedFaq, "The first study was well-designed there was a control group and [it was done] double-blind. After 24 weeks, a good response was noted in 30% of the subjects treated with kinetin [but] there was no statistically significant difference between the people taking kinetin and the people just getting the placebo." Another study was then performed that did not use a placebo control group, but in which everyone was using a product that contained some amount of kinetin. Not surprisingly, in this protocol the results for skin were much better. "Essentially all of the subjects reported improvement after 24 weeks" regardless of how much kinetin the product contained. As MedFaq states, "This outcome could also have a variety of causes unrelated to kinetin: It could reflect an improvement over time, a change across seasons, the subjects' enthusiasm, or it could have been caused by the cream or lotion the kinetin is in. In the first study, all of the subjects followed a standard skin care regimen consisting of a gentle-skin cleanser and daily use of sunscreen.' If that regimen was followed in the second experiment, it too might explain the improvement."

Despite the overly indulgent interpretation of these two studies by Senetek and those companies that buy kinetin from Senetek, there is intriguing fruit-fly and in vitro research concerning kinetin in regard to its cellular anti-aging affects (Sources: Biochemical and Biophysical Research Communications, June 1994, pages 665-672; and Biochemical and Biophysical Research Communications, November 1999, pages 499-502). Almost all of this published research was conducted by Dr. Suresh I. S. Rattan, PhD, DSc. In an interview I had with Dr. Rattan, associate professor of biogerontology at the University of Aarhus, Denmark, he stated that "Topically no one knows how or if N6-furfuryladenine is being taken up or used by the cell [but] We are curious about negative effects In cell cultures when a concentration of, say, 250 micromolars of N6-furfuryladenine was used, we got good results, but when we used 500 micromolars of N6-furfuryladenine, the cells started dying." In other studies Rattan conducted where flies were fed kinetin they sometimes lived, but they also died if the dose was just varied slightly. The possibility that kinetin may cause cell death has been investigated in other research as well (Source: Cell Growth and Differentiation, January 2002, pages 19-26). That may not be good news. I suspect that when applied topically kinetin can't exert any effect on the life span of the cell, which is good news. Even if it could somehow be utilized, there probably isn't enough kinetin in any product to have a negative or positive impact, but that is only a guess?no one knows for sure.

One recent study showed kinetin to have no antioxidant properties (Source: Bioorganic and Medicinal Chemistry, May 2002, pages 1581-1586), though there is other research suggesting it can (Source: Biochemical and Biophysical Research Communications, October 2000, pages 1265-1270).

kiwi fruit extract. As a food, kiwi has significant antioxidant properties that may even be greater than those of vitamin C (Source: Nutrition and Cancer, 2001, volume 39, number 1, pages 148-153). Whether that benefit translates to its use on skin has not been demonstrated. The acid component of the kiwi can be a skin irritant.

Kniphofia uvaria nectar. Derived from the plant also known as red hot poker or torch lily. There is no research showing this to have any benefit for skin.

Ko ken. See kudzu root.

kojic acid. By-product in the fermentation process of malting rice for use in the manufacture of sake, the Japanese rice wine. There is definitely convincing research, both in vitro and in vivo, and also in animal studies, showing that kojic acid is effective for inhibiting melanin production (Sources: Biological and Pharmaceutical Bulletin, August 2002, pages 1045-1048; Analytical Biochemistry, June 2002, pages 260-268; Cellular Signaling, September 2002, pages 779-785; American Journal of Clinical Dermatology, September-October 2000, pages 261-268; and Archives of Pharmacal Research, August 2001, pages 307-311). Both glycolic acid and kojic acid, as well as glycolic acid with hydroquinone are highly effective in reducing the pigment in melasma patients (Source: Dermatological Surgery, May 1996, pages 443-447). So why aren't there more products available containing kojic acid? Kojic acid is an extremely unstable ingredient in cosmetic formulations. Upon exposure to air or sunlight it turns a strange shade of brown and loses its efficacy. Many cosmetics companies use kojic dipalmitate as an alternative because it is far more stable in formulations. However, there is no research showing that kojic dipalmitate is as effective as kojic acid, though it is a good antioxidant. There is a small amount of research showing kojic acid to be a skin irritant (Source:, "Skin Lightening/Depigmenting Agents," November 5, 2001).

kola nut. One of the major components of the kola nut is caffeine, which can be a skin irritant. However, kola nut also has a primary amine content that can form nitrosamines, which are potential carcinogens (Source: Food and Chemical Toxicology, August 1995, pages 625-630). See also caffeine.

konjac powder. A dietary fiber that is highly absorbent, but not more so than other food substances (cornstarch for example) or nonfood substances (like talc, magnesium, or other minerals). If you have problems with breakouts, any oil-absorbing substance can be helpful for skin; however, adding absorbents in the form of food ingredients can increase the bacteria content in skin.

Krameria triandra extract. Derived from the plant commonly known as rhatany, it has a high tannin content and skin-constricting properties, making it a potential skin irritant. However, it also has antioxidant properties (Source: Planta Medica, March 2002, pages 193-197).

kudzu root. Source of isoflavone, genistein, and daidzein, all plant estrogens (Sources: Phytochemistry, June 2002, pages 205-211; and Journal of Alternative Complementary Medicine, Spring 1997, pages 7-12). It can be a potent antioxidant.

kukui nut oil. Non-volatile oil from a plant native to Hawaii; it has emollient properties for skin (Source: Journal of the Society of Cosmetic Chemists, September-October 1993).