Curr Allergy Asthma Rep (2012) 12:590–598 DOI 10.1007/s11882-012-0294-z PEDIATRIC ALLERGY AND IMMUNOLOGY (JM PORTNOY AND CE CIACCIO, SECTION EDITORS) Medical Causation and Expert Testimony: Allergists at this Intersection of Medicine and Law Howard M. Weiner & Ronald E. Gots & Robert P. Hein Published online: 29 August 2012 # The Author(s) 2012. This article is published with open access at Springerlink.com Abstract Clinical practice always necessitates proper diag- nosis and correct treatment. For most clinical fields, determin- ing the cause of the illness is irrelevant to the intervention. An oncologist, for example, has no need to explore the “cause” of the patient’s lymphoma. Allergists, by contrast, have tools and the need to examine the relevant allergen which is the putative “cause” of the patient’s allergic symptomatology. In the con- text of a legal claim, the “cause” of the symptoms or disorder is central, because it determines financial responsibility. How- ever, in the case of an allergic disorder and identified allergen, a claim requires more. Whose allergen? Where did it come from? These are crucial questions that must be answered. This paper explores the approaches to causal assessment which are important for the clinical allergist as he/she navigates the interface between clinical practice and legal proceedings. Its purpose is to help the allergist understand that interface, and to be prepared to enter an unfamiliar legal arena. Keywords Causation . Causation analysis . Medical/legal . Source identification . Differential diagnosis . Differential diagnosis vs. Causation H. M. Weiner (*) Medical Assessment Institute, Inc, 2385 NW Executive Center Drive, Boca Raton, FL 33431-8510, USA e-mail: howard@hmweinermd.com R. E. Gots International Center for Toxicology and Medicine, Rockville, MD 20850, USA e-mail: rgots@ictm.com R. P. Hein Fowler, Hein, Cheatwood & Williams PC, 2970 Clairmont Road NE Suite 220, Atlanta, GA 30329‐4414, USA e-mail: robinhein@apartmentlaw.com Introduction Diagnosis, treatment, and prevention are the primary roles of the practicing physician. What is wrong with the patient? How do I treat him? How do I keep him well? Causal analyses are secondary, and, for most clinical fields, entirely unimportant. It does not much matter to an oncologist, for example, what caused the patient’s leukemia. The patient will frequently ask or supply his own theories, but the therapeutic intervention is determined by the diagnosis, not the etiology. By contrast, legal disputes, as opposed to clinical ones, almost always involve causal questions and demand causal answers. Did the contaminated drinking water cause the cancer? Did formaldehyde from the insulation cause the chronic rhinitis? Did the mold in the home arising from a leaking roof or window cause the child’s asthma? Did the asbestos in the workplace cause the lung cancer or was it the 40 pack-years of cigarette smoking? The answers to such questions are central to asserting liability claims against the polluter, the insulation installer, the home builder, or the asbestos producer in a court of law. Allergists, as distinguished from oncologists, rheumatolo- gists, and orthopedic surgeons frequently address the ques- tion, “What caused the patient’s allergy?” This clinically important causal question, when addressed, may require fas- tidious history taking and diagnostic approaches such as al- lergy skin testing and other diagnostic inhalational/dermal/ oral/subcutaneous challenges. Since not all patients who are skin tested demonstrate clinical concordance with the history elicited, that question may have a presumptive, but unproven answer. For example, was it allergic versus vasomotor rhini- tis? Or was it allergic versus irritant-induced asthma. In the context of a lawsuit, an allergist’s working diagnosis is insuf- ficient. A supportable, final diagnosis is necessary. Another, less familiar, causal question is also demanded in legal proceedings. In addition to a determination of which