ubiquinone. See coenzyme Q10.

ultramarines. Inorganic pigments (of various colors) permanently listed by the FDA for external use only, including around the eye area.

Ulva lactuca extract. Extract from the plant known as sea lettuce, it has some anti-inflammatory and antioxidant properties for skin (Source: Phytotherapy Research, December 2000, pages 641–643). However, there is no research showing that it has any benefit for cellulite reduction.

Undaria pinnatifida. Form of brown algae. See algae.

urea. Component of urine, although synthetic versions are used in cosmetics. In small amounts urea has good water-binding and exfoliating properties for skin; in larger concentrations it can cause inflammation (Source: Skin Pharmacology and Applied Skin Physiology, January-February 2002, pages 44–54).

Urtica dioica. See nettle extract.

UVA. Ultra-violet A radiation. The sun produces a range of ultraviolet (UV) radiation, of which UVA and UVB affect our skin. 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 visible 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, thickening of the stratum corneum (outer layer of skin), 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 truly effective and beneficial for skin, sunscreens must protect skin from both the sun’s UVA and UVB radiation. In the United States, there are four ingredients approved by the FDA that protect across the full UVA range: titanium dioxide, zinc oxide, avobenzone (also called Parsol 1789 and butyl methoxydibenzoylmethane), and Mexoryl SX (ecamsule). Outside the United States, Tinosorb is another. Mexoryl SX is a L’Oreal-patented sunscreen ingredient that received FDA approval in July 2006 for use in a single sunscreen, Anthelios SX SPF 15, from the L’Oreal-owned line La Roche-Posay. This is the only sunscreen with Mexoryl SX that is approved for sale in the United States (Sources: International Journal of Pharmaceutics, June 2002, pages 85–94; Photodermatology, Photoimmunology, Photomedicine, August 2000, pages 147–155 and www.photodermatology.com/sunprotection.htm; Skin Therapy Letter, volume 2, number 5, 1997; and www.fda.gov/bbs/topics/NEWS/2006/NEW01417.html). However, L’Oreal has been adding Mexoryl SX to products in their namesake line as well as in other lines they own, including Lancome and Kiehl’s.

Uva ursi extract. See arbutin and bearberry extract.

UVB. Ultra-violet B radiation. See UVA.