Based on the workshop on standardizing methods of assessing causality of adverse drug reactions held 14 18 june 1981 in morges switzerland and sponsored by. Allergic drug reactions account for only 5 to 10 of all adverse drug reactions any medication has the potential to cause an allergic reaction skin reactions eg urticaria erythema are the most common form of allergic drug reaction but can also include cough nausea vomiting diarrhea and headaches and in severe cases can cause anaphylaxis. Adverse event ae is a difficult process if a causal relationship can be confirmed an ae is referred to as an adverse drug reaction adr the reported signs or symptoms of an ae could be due to the drug the underlying disorder or other unrelated or concurrent factors the conventional approach to defining adrs. Numerous methods for causality assessment of adverse drug reactions adrs have been published the aim of this review is to provide an overview of these methods and discuss their strengths and. The adverse drug reaction adr causality assessment is a routine procedure in pharmacovigilance 1 because it allows assessing drug safety parameters and the relationship and likelihood between drug exposure and the occurrence of adr of health technologies in the post marketing period