Ubiquinone - UVB

Beauty and Cosmetic Glossary - U

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ubiquinone. See coenzyme Q10.

Ulva lactuca extract. Extract of the plant known as sea lettuce. It has some anti-inflammatory and antioxidant properties for skin (Source: Phytotherapy Research, December 2000, pages 641-643).

umbilical extract. Obtained from either human or animal umbilical cord. It is used in cosmetics with varying, though unsubstantiated, claims about the effect on skin. Use of animal- and human-derived ingredients is prohibited under the provisions of the European Union Cosmetics Directive. For animal-derived ingredients, this is based on concerns about transmission of bovine spongiform encephalopathy (Mad Cow Disease); for human-derived ingredients the concern is viral diseases such as human immunodeficiency virus (HIV) (Source: International Journal of Toxicology, 2002, volume 21, Supplement 1, pages 81-91). There is no way to know from reading a cosmetic ingredient label what the source of the extract is.

Uncaria gambir extract. Leaf extract of a shrub from the madder family. Some forms of uncaria have antioxidant properties. There is no research for the gambir variety. However, due to its tannin content, Uncaria gambir most likely has antioxidant properties, though the tannin content also makes it a potential skin irritant.

Undaria pinnatifida. Form of seaweed. See algae.

Urtica dioica. See nettle extract.

usnic acid. Antibacterial and possibly anti-inflammatory substance derived from lichens (Sources: Fitoterapia, September 2000, pages 564-566; and European Journal of Pharmaceutical Sciences, April 1998, pages 141-144). It can also inhibit cell production (Source: Cellular and Molecular Life Sciences, August 1997, pages 667-672).

UVA. Ultra-violet A radiation. The sun produces a range of ultra-violet (UV) radiation. Skin damage such as wrinkling, skin discoloration, sagging, and coarse texture is a consequence of unprotected sun exposure due to the cumulative effect of the suns UV radiation. UVA and UVB radiation are the portions of the suns rays that cause this damage. UVA rays have wavelengths of 320 to 400 nanometers; UVB rays have wavelengths of 290 to 320 nanometers. UVB radiation causes sunburn, while UVA radiation does not produce any short-term evidence of skin damage. Nonetheless, UVA radiation creates serious cumulative changes in skin that may be far greater than the sunburn caused by UVB radiation. Research has shown that unprotected exposure to UVA rays can, within one week, create distinct injury, such as inflammation, abnormal cell production, stratum corneum (outer layer of skin) thickening, depletion of immune-stimulating cells, and evidence of the possibility of elastin deterioration (Sources: Journal of the American Academy of Dermatology, May 2001, pages 837-846; Bulletin of the Academy of National Medicine, 2001, volume 185, number 8, pages 1507-1525; Photodermatology, Photoimmunology, and Photomedicine, August 2000, page 147; and Journal of the American Academy of Dermatology, January 1995, pages 53-62).

To be effective, sunscreens must protect skin from both the suns UVA and UVB radiation. In the United States, there are only three ingredients that are approved by the FDA that protect across the full UVA range: titanium dioxide, zinc oxide, and avobenzone (also called Parsol 1789 and butyl methoxydibenzoylmethane). Outside of the United States, Mexoryl SX is also used. (Sources: International Journal of Pharmaceutics, June 2002, pages 85-94; Photodermatology, Photoimmunology, Photomedicine, August 2000, pages 147-155 and www.photodermatology.com/sunprotection.htm; and Skin Therapy Letter, Volume 2, Number 5, 1997.)

The SPF (sun protection factor) number on sunscreens relates only to a product's efficacy against UVB exposure. There is no rating system for UVA protection. The only way to tell if a product can protect skin from UVA radiation is to note that at least one of the ingredients mentioned above is listed among the active ingredients on the label. Because UVA protection is so important, all sunscreen products must contain one or more UVA-protecting ingredients. See sunscreen, and sun protection factor.

Uva ursi extract. See arbutin, and bearberry.