Clinical ecology was the name given by proponents in the 1960s to a claim that exposure to low levels of certain chemical agents harm susceptible people, causing multiple chemical sensitivity and other disorders. Clinical ecologists are people that support and promote this offshoot of conventional medicine. They often have a background in the field of allergy or otorhinolaryngology, and the theoretical approach is derived in part from classic concepts of allergic responses, first articulated by Theron Randolph and developed by Richard Mackarness.
Clinical ecologists support a cause-and-effect relationships for non-specific symptoms reported by some people after low-dose exposure to chemical, biologic, or physical agents. This pattern of low-dose reaction is not generally accepted by toxicologists. Although some of the mainstream medical community continue to reject these claims, the concept is gaining some recognition under the modern and more clearly articulated classification of environmental medicine.
“Clinical Ecologist” is an environmental approach that is consistent with the practice of holistic medicine. Practitioners with this orientation do not use the term “Clinical Ecologist,” although those opposed to this complementary medicine approach to illness often still do. Unlike terms such as physician or nurse, the term clinical ecologist is not legally regulated in any jurisdiction, which means that any person may legally claim to be a clinical ecologist. If wanted, they may obtain an extralegal certification or membership from the unregulated private organization American Academy of Environmental Medicine upon payment of a fee.
Many clinical ecologists are traditionally licensed healthcare professionals who hold advanced traditional medical certifications. Others may have a more alternative training. 
Randolph published a number of books to promote clinical ecology and environmental medicine, including:
Randolph, Theron G. (1962). Human ecology and susceptibility to the chemical environment. Springfield, Ill: Thomas. ISBN 0-398-01548-1.
- Moss, Ralph W.; Randolph, Theron G. (1980). An alternative approach to allergies: the new field of clinical ecology unravels the environmental causes of mental and physical ills. New York: Lippincott & Crowell. ISBN 0-690-01998-X.
- Randolph, Theron G. (1987). Environmental medicine: beginnings and bibliographies of clinical ecology. Fort Collins, CO: Clinical Ecology Publications. ISBN 0-943771-00-5.
In 1965, Randolph founded the Society for Clinical Ecology as an organization to promote his theories based on the symptoms of his patients, known as multiple chemical sensitivities (MCS).
During the 1980s the movement was rejected by some medical organizations and judges, and health insurance companies often refused to pay their bills. The society’s name was changed from the Society for Clinical Ecology, according to its opponents, in order to flee from its bad reputation.
Despite the confusion in the traditional medical establishment regarding the classification and treatment of MCS, MCS has achieved credibility in workers compensation claims, tort liability, and regulatory actions. The pragmatic determination of MCS includes four elements: (1) the syndrome is acquired after a documentable environmental exposure that may have caused objective evidence of health effects; (2) the symptoms are referable to multiple organ systems and vary predictably in response to environmental stimuli; (3) the symptoms occur in relation to measurable levels of chemicals, but the levels are below those known to harm health; and (4) no objective evidence of organ damage can be found.