Anything with a pH higher than 7 is alkaline; a pH below 7 is acidic. Water has a pH of 7; skin has an average pH of 5.5. Skin irritation can be caused by products with a pH of 8 or higher (Sources: eMedicine Journal, January 7, 2002, volume 3, number 1, www.emedicine.com; Cutis, December 2001, Supplemental, pages 12–19; and Contact Dermatitis, April 1996, pages 237–242). Also, research indicates that the bacterium that causes acne, Proprionibacterium acnes, proliferates when the skin is more alkaline (Sources: Infection, March–April 1995, pages 89–93; and Journal of Antimicrobial Chemotherapy, September 1994, pages 321–330).