While there is no international standard for defining the diversity of allied health professions, they are typically considered those which are distinct from the fields of medicine, nursing and dentistry.
[3] In most jurisdictions, AHPs are subject to health professional requisites including minimum standards for education, regulation and licensing.
[3] They may sometimes be considered to perform the role of mid-level practitioners, when having an advanced education and training to diagnose and treat patients, but not the certification of a physician.
Allied health professionals are different from alternative medicine practitioners, also sometimes called natural healers, who work outside the conventions of modern biomedicine.
Together with a range of technical and support staff they may deliver direct patient care, rehabilitation, treatment, diagnostics and health improvement interventions to restore and maintain optimal physical, sensory, psychological, cognitive and social functions.
These factors may include AHPs offering services in ways which support treatments provided by other healthcare professionals (working either in independent autonomous practice or under direct supervision), or by offering services which other healthcare professionals require but do not provide themselves (for example in the use of medical technologies).
[15] The explosion of scientific knowledge that followed World War II brought increasingly sophisticated and complex medical diagnostic and treatment procedures.
[20] In the United Kingdom there are 12 distinct professions who are considered allied health professionals; in combination they account for about 6% of the NHS workforce.
This is primarily due to expansion of the health industry due to demographic changes (a growing and aging population), large numbers of health workers nearing retirement, the industry's need to be cost efficient, and a lack of sufficient investment in training programs to keep pace with these trends.
[27] Advancements in medical technology also allow for more services that formerly required expensive hospital stays to be delivered via ambulatory care.