Alternative medicine is any practice claiming to heal "that does not fall within the realm of conventional medicine." It may be based on historical or cultural traditions, rather than on scientific evidence.[citation needed]
A 1998 systematic review of studies assessing its prevalence in 13 countries concluded that about 31% of cancer patients use some form of complementary and alternative medicine. Alternative medicine varies from country to country. Jurisdictions where alternative medical practices are sufficiently widespread may license and regulate them. Edzard Ernst has said that in Austria and Germany complementary and alternative medicine is mainly in the hands of physicians, while some estimates suggest that at least half of American alternative practitioners are physicians. In Germany herbs are tightly regulated: half are prescribed by doctors and covered by health insurance based on their Commission E legislation.
Alternative medicine is frequently grouped with complementary medicine or integrative medicine, which, in general, refers to the same interventions when used in conjunction with mainstream techniques, under the umbrella term complementary and alternative medicine, or CAM. Some researchers in alternative medicine object to this categorization, preferring to emphasize differences of approach, but nevertheless use the term CAM, which has become standard. Critics maintain that the terms “complementary” and “alternative medicine” are deceptive euphemisms meant to give an impression of medical authority.