Placebos are widely used in medical research and medicine, and the placebo effect is a pervasive phenomenon ; in fact, it is part of the response to any active medical intervention.

Placebos were widespread in medicine until the 20th century, and they were sometimes endorsed as necessary deceptions.

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.

Critics maintain that the terms “ complementary ” and “ alternative medicine ” are deceptive euphemisms meant to give an impression of medical authority.

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 .< ref name = Ernst_Cassileth > Alternative medicine varies from country to country.

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.

While one-third of alternative treatments have some published literature supporting their use, research on alternative medicine is frequently of low quality and methodologically flawed, which might cause these results to be exaggerated.

The term ' alternative medicine ' is generally used to describe practices used independently or in place of conventional medicine.

The terms ' integrative ' or ' integrated medicine ' indicate combinations of conventional and alternative medical treatments that have some scientific proof of efficacy ; such practices are viewed by advocates as the best examples of complementary medicine.

Ayurveda, Chinese medicine, Homeopathy and Naturopathy are cited as examples The term appears to have entered into usage through the National Institute of Health's National Center for Complementary and Alternative Medicine ( NCCAM ), which began to employ it as a substitute for alternative medical systems as a way of differentiating widely comprehensive systems of medicine, such as Ayurvedic medicine, from specialized alternative approaches.

Ralph Snyderman and Andrew Weil state that " integrative medicine is not synonymous with complementary and alternative medicine.

Some alternative medicine proponents postulate a widespread occurrence of systemic candidiasis ( or candida hypersensitivity syndrome, yeast allergy, or gastrointestinal candida overgrowth ), a medically unrecognised condition.

It is generally categorized as complementary and alternative medicine ( CAM ).