Health science is the name given to the helping professions that use applied science to improve health and to treat disease. There are a number of very different disciplines within the health sciences, each with its own training and educational requirements for practice. Outside of having a basis in biologic science and a common goal of easing the effects of illness, there are other important similarities between these health science disciplines. Those similarities have to do with responsibility and duty to the client, and those obligations exist as both professional and legal requirements of each occupation. Because health science professionals are entrusted with the personal secrets of their clients (patients), and because their decisions directly influence their clients' lives, almost all countries have some kind of licensing requirement for practitioners of the allied health sciences. Through these licensing requirements, the scope of practice for each of the health science professions is regulated.
Care versus Science
Of course, not all health care practitioners are involved in the health sciences, whether or not a license to practice is required. Healing arts developed long before the sciences matured, and traditional practices are the mainstay of health care in many communities in the world. Even if these practices are quite effective, they are not part of health science. A chiropracter can often rid a patient of troublesome back pain but, because the chiropracter's view of the causes of pain and the workings of the human body does not have a firm grounding in human biology, Chiropractic is not included here as one of the allied health sciences, but instead as part of alternative medicine.
Collaboration between the allied health science professions can act as a check and balance against medical errors and offer better health care. For example, when a patient in the hospital is given a powerful drug through an intravenous drip, several different kinds of health professionals are directly involved in that single treatment. Most typically the physician orders the drug, the pharmacist prepares it, and the nurse administers it. Each of these professionals evaluates the patient either directly by an interview and examination, or indirectly through review of the medical record. Each professional brings a different perspective to the same treatment, and, working together, increases the liklihood that the patient will receive proper care. When treatment of a disease is very complex, and requires many different treatments along with a variety of different tests and examinations of the body, effective care demands the co-ordinated efforts of an entire team of health science professionals.
Until recently, there has been little training of teams composed of different kinds of healthcare professionals in the formal mechanics of working together. However, as medical care has become increasingly complex, some educators have now focused on this aspect of training. 
Upward mobility for the Allied Health Professions within the structure of healthcare organizations is also a current issue in the field. Management positions in hospitals and other healthcare institutions have traditionally been accessible to nurses and physicians, but much less commonly attained by other categories of health science professionals. 
The profession of medicine first moved to a biologic basis around the Eighteenth Century, and physicians began gradually culling practices that either (1) could not be rationalized with a scientific explanation or (2) could not be proven effective through an examination of evidence using the scientific method. This refinement of medical practice from traditional western practices into an application of human biology is still occurring at the present time. Physicians have provided authoritative direction for the care of the sick and injured since ancient times in western civilization. Many societies, up until the mid-Twentieth Century, restricted the certification of physicians to qualified men. Although female physicians are now trained in roughly equal numbers to males, the medical profession remains, worldwide, predominantly male.
Nursing became a health science in the Nineteenth Century, primarily through the efforts of Florence Nightingale, who not only transformed the bedside care of the sick into a profession, but also spearheaded the imposition of sanitary condition in hospitals and infirmaries. At the time nursing joined the health sciences, the bedside care of the sick was overwhelmingly the province of women. Nursing remains predominantly female, although male nurses have long been included in the profession. Until women became welcomed into schools of medicine, a phenomonom thaat did not occur in the United States until the last quarter of the Twentieth Century, women with an strong interest in medicine often trained as nurses.
Rehabiliation of the seriously injuried and disabled became a recognized field of medicine after World War II. Along with the medical specialty of physiatry (rehabilitation medicine), the professions of physical therapy and occupational therapy became established.
See Medical research.
- Art therapy
- Dance therapy
- Medical technology
- Nutritional science
- Occupational therapy
- Physical therapy
- Respiratory therapy
- Speech-language pathology
- Medical informatics
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